Pump and tank advice, please, borehole supply in the UK

[Jeremy Harris]

Hi,

I live in England, where it is rare for people to have a private well water supply. One consequence of this is that there are not many companies around who have a lot of knowledge about boreholes for private house water supplies, and I have been really struggling to get good advice. I've read a lot on this forum and it's clear that there are some very knowledgeable and experienced people here, so after having struggled for well over a year to get a good, working, borehole system I'd like to describe my proposed system and hopefully explain why I want to change things. I wish I were as lucky as you folk in the US, where it seems having a well water supply is pretty normal, rather than the rarity it is here in England. Please excuse the units, we're metric here but I'll try and convert to US units to make things easier to understand where I can. I also apologise for this being a long first post, but thought it'd help if I tried to give as much background as possible.

Our borehole was drilled through 40m (around 130 ft) of hard clay, then through a few metres of running greensand (where the aquifer is) and then down into the underlying sandstone. The total drill depth was 65m (~ 212ft). The drill job was not a good one, and the drillers didn't know they had hit water, as they were wet drilling with polymer mud and the black clay coming up into the settling tanks was making it hard to see what they were drilling through. We were going to abandon the hole as being dry when one driller decided to come back the next day to test pump it and found we had a yield of at least 4,000 litres per hour (about 1000 US gallons per hour), with only a few metres drop in level after pumping for a couple of hours.

We decided to line the hole and use it, so dropped in 15m (~50 ft) of 125mm (~5 inch) OD perforated PVC screen, with a cap on the bottom, followed by 125mm liner to the well head. The lower 25m (~80ft) or so of the space around the lining was packed with graded crushed glass as filter pack, then the remainder of the liner was sealed to the bored hole with bentonite, to stop surface water running down. A concrete cap and manhole cover was fitted on the top to cover the well head. A Grundfos SQ1-65 pump was lowered in to 45m (~ 146 ft)down, so 20m (~65 ft) off the bottom. The rest water level in the hole is around 3.5m (~11 ft) from the surface.

The first problem (I know now, but didn't a year ago) is that the driller didn't develop the well, but left it. It sat unused while we built a new house. After around 6 months I connected up the pump and started checking the well out. The pump would easily pump 1400 litres per hour (about 370 US gals/hour) for days on end, with the water level in the well dropping to around 12m from the surface (so a drop of about 25 to 30 ft from the rest water level). I pumped the well hard like this for a couple of weeks, at the recommendation of the driller, but it kept pumping lots and lots of greensand.

I pulled the pump up, extended the pipe and cable and tried lowering it further, but found it wouldn't go down at all, it hit what we think is hard-packed sand, right below where the pump was sat (so the bottom 20m (~ 65ft) of the well is filled with packed sand. The driller came back to pull the pump out and try and airlift the sand out, but it was too solid to shift. He suggested I pull the pump up, as the water level is always high. I raised the pump by 20m (~65ft) and as long as I don't pump hard I get clean water, far more than I need to run the house, so I'm going to leave the well as it is, even though is has sand in the bottom, and maybe revisit the well problem later.

The water analysis showed we had hard water, pH around 8, TDS around 380 with a moderate iron content and a tiny bit of stinky Hydrogen Sulphide. The drillers knew nothing about filtration or treatment, so I was on my own. I found a pretty good filter system that works well, and uses a sand/Aquamandix media and an air pocket at the top with a spray to oxidise incoming water before it flows down through the filter. This does a great job at getting the iron and hydrogen sulphide out and the water only needs fine filtering, UV sterilisation and softening to be really nice. The filter, steriliser and softener all work fine, with no problem.

The iron filter needs a high backwash flow rate (around 30 litres/min, or ~ 8 US gallons a minute) If I pump this hard from the well I draw up sand after ten minutes or so. To stop the pump from drawing sand I need to keep the flow rate down below 10 litres/min (~2.6 US gal/min). The drillers suggested I fit a break tank, fill the break tank with water from the pump, with a restrictor to keep the flow rate down, then use a second pump to charge the pressure tank and run the house supply drawing from the break tank. This works fine, but is pretty complicated and takes a lot of space up. I have a 650 litre (~170 US gal) break tank, with a float switch, plus a 1hp pump and a 300 litre (~80 US gal) pressure tank, just so I can backwash the iron filter. Apart from taking up a load of space, I have to protect the external break tank from freezing in winter and have the noise of the 1hp supply pump (basements are rare in British houses, so the pump and filter is in a small shed on the side of the house).

I'd like to make the system a bit simpler, and work on just the borehole pump. That can deliver loads of pressure, but has to be restricted to 10 litres/min so that it doesn't draw up sand (which is OK, it's about what the shower uses, and that's the biggest water draw we have). I have room for a second 300 litre pressure tank in the shed, so am thinking of the following system, to get rid of the break tank and the second pump.

Keep the restrictor in the borehole pump and feed it direct to two 300 litre pressure tanks in parallel, charged to 5 bar, so basically two 80 US gal pressure tanks running at about 74 psi max. The filter back flush takes 8 minutes at 30 litres/minute maximum (from the spec sheet, it actually seems to draw about 26 litres/min on back flush, measured). I reckon that, with the pump kicking in to deliver 10 litres/min, plus the usable reserve of around 200 litres in the two pressure tanks, that should be OK for the back flush requirement (this is based on my calcs of the drawn down volume and pump switch on point), The first question is, does this sound like a sensible think to do?

From my perspective, if it would work OK, then it has a load of advantages. I can get rid of the big break tank and get rid of the 1hp second pump. I can simplify the wiring so that the borehole pump is just switched from the pressure switch. The system will be a lot quieter (except when doing a short backwash) as I no longer have the extra 1hp pump. There seems less to go wrong if I just have the pressure tanks, pressure switch, borehole pump and filter system.

In case the above isn't enough detail, the iron/H2S filter is a 1252 vessel with a Clack WS1 head and an air draw kit, designed and set up to have an air bubble at the top in use. It's big for our needs (we use around 250 litres/day, about 66 US gals a day), and we have it set to back wash every three days, which seems fine for keeping the iron levels well down and getting rid of the H2S. We have a 5 micron pleated polyester filter after this, then a UV steriliser (sterilisation is mandatory here, even though the water tested clear for bacteria). The softener is inside the house, a Harvey unit that works very well. We run the water system at 5 bar (~74 psi) right up to other side of the softener, then have a pressure reducing valve that drops the house supply down to 2.5 bar (about 37 psi). I've done this so that variations in pressure vessel pressure between pump on and off and the slight pressure losses through the filters etc, don't show up on the house supply.

Sorry this is a long post, I guess what I'm really looking for is just either confirmation that I'm on the right track, or being told I have it wrong and should just leave things as they are.

I have an additional question about sterilisation, but it seems rude to add that along with the above lengthy post.

Many thanks in advance for your patience in having read this far.

Jeremy

 

[Valveman]

I think you would be better off staying with the break tank and the extra booster pump. You could use a submersible pump in the break tank as it would be much more quite.

Your idea would work if you could make sure the two pressure tanks were always full (50 gallons stored) but you cannot. If you have used water over time, the pressure in the pressure tanks could be (Murphys law say it will be) at 55 PSI when using a 55/75 pressure switch. This means your pressure tanks are empty when you need the water. So when the pump comes on it must supply your demands, while at the same time it sees the pressure tanks as an additional demand that needs to be filled. You will have no reserve of water over the 2.5 GPM the pump can supply, so the pressure will continue to decrease.

The break tank will always be full of water when you need it, and the extra pump can supply that water at whatever flow rate is needed. I would not even use a very large pressure tank with the extra booster pump, as that will just be an additional load that must be filled with water from the break tank.

 

[Sponsor]

 

[Reach4]

The driller came back to pull the pump out and try and airlift the sand out, but it was too solid to shift.

Was what the driller did was to use a realy big compressor and blow air down the hole creating a geyser, or was it a pipe and hose system called an air lift pump and a smaller compressor?

Is your sand really green? It is not important for the purpose, but I am just curious.

Sounds like to me that the driller should have used a finer screen for the PVC. I am not a pro.

 

[Jeremy Harris]

I think you would be better off staying with the break tank and the extra booster pump. You could use a submersible pump in the break tank as it would be much more quite.

Your idea would work if you could make sure the two pressure tanks were always full (50 gallons stored) but you cannot. If you have used water over time, the pressure in the pressure tanks could be (Murphys law say it will be) at 55 PSI when using a 55/75 pressure switch. This means your pressure tanks are empty when you need the water. So when the pump comes on it must supply your demands, while at the same time it sees the pressure tanks as an additional demand that needs to be filled. You will have no reserve of water over the 2.5 GPM the pump can supply, so the pressure will continue to decrease.

The break tank will always be full of water when you need it, and the extra pump can supply that water at whatever flow rate is needed. I would not even use a very large pressure tank with the extra booster pump, as that will just be an additional load that must be filled with water from the break tank.

Very many thanks, I think you've found the flaw that I just failed to spot, over-thinking it I think. You're absolutely right, the pressure in the tanks could be right at the lower limit when the filter calls for backwash, which would dramatically reduce the available volume and pressure needed to lift the heavy filter media and clean it. I'll have to have a think and see if there is a way I can resolve this, as getting rid of the break tank would solve a few other access problems around the rear of the house.

One quick fix that I've literally just though of, is that the tank pressure switch always runs to full pressure and then cuts off when the power is interrupted (it's an optical switch, with two movable beam-break sensors that are triggered by the needle on the pressure gauge). If I was to fit a time switch, that turned off the borehole pump power every night for a few minutes, an hour or two before the filter back washes at 2 am, then the tanks should always be full. I'll sleep on it, and see if the idea still makes sense tomorrow!

Thanks again for highlighting the flaw in my thinking, it's very much appreciated.

 

[Valveman]

If I was to fit a time switch, that turned off the borehole pump power every night for a few minutes, an hour or two before the filter back washes at 2 am, then the tanks should always be full.

Something like that could work if you can figure out how to make the timer turn the pump on, and still use the pressure switch to turn it off. Otherwise if the tanks are empty the timer might not be set long enough, but if the tanks were fairly close to full the timer might run the pump too long, which could cause high pressure problems and maybe even deadhead the pump.

Oh and I agree with Reach that if you could clean up the well it would be better to have the volume available from the source.

 

[Jeremy Harris]

Was what the driller did was to use a realy big compressor and blow air down the hole creating a geyser, or was it a pipe and hose system called an air lift pump and a smaller compressor?

Is your sand really green? It is not important for the purpose, but I am just curious.

Sounds like to me that the driller should have used a finer screen for the PVC. I am not a pro.

The drillers turned up with a massive compressor, towed behind a truck. They connected this via a small (around 3/8" maybe 1/2") airline to a sort of home made air injector. This looked to be a bit of taped clear air hose poked into a bit of 1" PVC rigid pipe. They screwed together enough lengths of this 1" PVC pipe to get to the packed sand layer, taping the air house to the side of it all the way. They could only crack the compressor valve open a fraction, as the truck-sized compressor they had was way to big, I think. All that happened was that the end of the PVC pipe got stuck in the packed sand and very little sand/water came up. If they lifted the pipe up then it would spurt water out, like in one of those videos, but very little sand. After I'd been paying them for around three hours, with nothing to show for it, I told them to pack it in and send me the bill.

The problem here in England is that there just isn't any real expertise in drilling well/boreholes, and once you have one drilled by one company, no other company wants to try and help out. It's a real headache trying to get hold of people who know what they are doing, so I've really been stuck trying to do a DIY job, with the aid of advice from forums like this.

The screen size may be a problem, but the driller reckons that the running sand should pack up around the crushed glass media and form a filter. I'm personally convinced that the real problem was that the driller didn't develop the well by pumping it hard as soon as it was completed, as I've read (and it could be wrong) that this helps to pull the fine sand out and allows the coarser sand to pack around the glass media to form a filter around the screen.

Yes, the sand really is green, a very dark green. It's pretty fine and settles to form a very hard layer.

I had seen that first YouTube video and I have made a gadget that is similar, with lots of lengths of threaded PVC pipe. I added a 28mm (1 1/8th inch) copper pipe on the lower section. with a sharpened end, and a brazed in copper air pipe, bent back up to squirt air up the pipe. I have a long length of airline and a small shop compressor, and plan to replicate what the chap in that YouTube video did, with the hope that the sharpened, bevelled end of the copper pipe might cut into the packed sand. I also added a valve on the top of the PVC pipe so I can blast air down to try and loosen the sand. I plan on giving it a try soon, to see if I can get the packed sand out.

 

[Jeremy Harris]

Something like that could work if you can figure out how to make the timer turn the pump on, and still use the pressure switch to turn it off. Otherwise if the tanks are empty the timer might not be set long enough, but if the tanks were fairly close to full the timer might run the pump too long, which could cause high pressure problems and maybe even deadhead the pump.

Oh and I agree with Reach that if you could clean up the well it would be better to have the volume available from the source.

I can easily try an experiment tomorrow, by switching the power off for a second and then back on again. I'm pretty sure the electronic pressure switch just automatically latches on until the cut off pressure when this happens, as I've heard the pump come on and run after I've turned the power off (I'm still building the house). I'll check and report back here, as it may be useful for others if it really does work like this.

Thanks again, I've had more useful advice from here in the past our or so than I've had from tens of hours trying to get well people here to sort this out!

 

[Jeremy Harris]

OK I've just tried an experiment by wiring up my spare pressure switch, to see what it does when the power goes off for an instant and then back on again. This is the type of pressure switch I have fitted to the top of my pressure tank: http://www.ebay.co.uk/itm/151020-Au...764?pt=LH_DefaultDomain_3&hash=item43cbbcef84 (I know that's an ebay link, but it is identical to the one that was supplied with my system).

This works by having two beam-break optical sensors that are turned on (left hand sensor) or off (right hand sensor) by the needle on the built-in pressure gauge. When the power goes off and then back on, provided the gauge needle isn't breaking the high pressure cut off sensor, the relay turns on to turn the pump on. The pump then runs until the needle breaks the high pressure cut off point. The selling point to me off this type of optical switch was that it didn't ice up in winter, which is, apparently, a problem with the standard spring loaded ones if exposed to cold.

This test confirms that if I were to add a simple time switch, to turn the pump power off for a minute or so, around an hour before the filter was due to backwash (which happens around 2am) then I could be near-100% certain that the tanks would be fully charged for the big pulse of water needed to lift the filter bed and backwash it. I already have a spare time switch in the shed, as I was using it to turn off the UV steriliser at night, to extend the tube life, but the building inspector didn't like that idea and wanted the steriliser on 24/7.

On the topic of sterilisers, has anyone any experience of the Doulton Rio 2000? Seems like a nice idea, using fine ceramic filters to get rid of bugs, but I have concerns over how frequently they clog up. My 5 micron filter catches fine grey/brown dust that I think comes from the Aquamandix media, and I have a feeling that some of that is probably fine enough to clog the pores of a ceramic filter. There seem to be a few online reviews saying these Doulton filters clog quickly too. Pity, as I like the idea of a steriliser that doesn't need any power (although I'm not sure our building inspector would approve of it, anyway).

 

[Reach4]

If you unplug your UV unit, it does not use power either.

For sanitizing, I like the method described here: http://www.moravecwaterwells.com/index.php/maintainance/disinfection-and-testing

What media does your planned iron+sulfur filter use? Katalox Light is good if you have enough backwash. Not cheap. Search it. It requires less backwash rate than many backwashing filters do. Since backwash rates are determined by the cross sectional area, a tall skinny tank will be better probably.

Your backwashing filter will filter out most of the stuff that your cartridge filter catches now. You normally want the backwashing filter first in line after the pressure tanks.

 

[Jeremy Harris]

If you unplug your UV unit, it does not use power either.

For sanitizing, I like the method described here: http://www.moravecwaterwells.com/index.php/maintainance/disinfection-and-testing

What media does your planned iron+sulfur filter use? Katalox Light is good if you have enough backwash. Not cheap. Search it. It requires less backwash rate than many backwashing filters do. Since backwash rates are determined by the cross sectional area, a tall skinny tank will be better probably.

Your backwashing filter will filter out most of the stuff that your cartridge filter catches now. You normally want the backwashing filter first in line after the pressure tanks.

Thanks, I used a similar sanitising method when I first commissioned the well, checking the pH and then using pool shock chlorine to sanitize the well, pipe work etc, as I initially had a small problem with iron bacteria (probably because the well wasn't commissioned properly in the first place). It seems fine now, and the water in the break tank tests clear, just with ferrous iron and the H2S smell, some of which oxides out in the tank. Nice to have it confirmed that what I did to sanitise the well and pipes seems to have been the right things to do.

The iron/H2S filter is a 1252 filter (so 12" diameter, 52" tall) and uses a mix of gravel at the very bottom, then Aquamandix and filter sand mixed. The media depth is a bit lower than for a plain sand or Birm filter, as it is arranged with an air head to better oxidise the H2S (and I guess the ferrous iron) as the water sprays through the air head to the filter bed. It's fitted directly after the pressure tank, via a check valve, to make sure it gets a good back wash flow.

The filter information I have says the back wash rate needs to be 8 to 10 US gals/min per square foot of media area. I make the media area just over 3/4 square foot, which suggests a back wash rate of between 6 and 8 US gal/min. In practice mine seems to draw around 7 US gal/min during back wash, which seems about right (I measured the level drop in the break tank to work out the rates). Back wash takes 8 minutes, followed by an air draw period of 15 minutes that uses a small amount of water (less than 10l/min, or ~2.6 US gal/min) to suck the water out of the filter. The filter then refills, compressing the air in it to a bubble at the top.

You're right, this iron filter takes out pretty much everything and the 5 micron pleated filter after it is really there to satisfy the building inspector. The specification for the UV steriliser says it has to have a 5 micron pre-filter, so I had to fit one (its a 10" big blue filter, with a washable filter element).

The house max water demand is about 10 l/min (~2.6 US gal/min) with the shower running, and everything else draws less flow. The total water used per day is usually less than 250 litres (around 66 US gals) as there are only the two of us. I probable made a rod for my own back by ordering too big an iron filter, as when I was advised to buy it I thought that over-sizing things would be a good idea. I now realise that by opting for the bigger filter I increased the back wash water demand, so I would have been better off using a skinnier tank and accepting the lower working throughput.

Still, we live and learn. Thanks to stuff I've read on this forum over the past 8 months or so I know a heck of a lot more about water supplies than I did when I had the well drilled. I've been kicking myself for not having read up on all this BEFORE choosing a well driller.....................

 

[Texas Wellman]

Can you get a sample of the sand and determine what the size is? If it's not too fine you might be able to fix it at the well since you already have a ~5" casing and have a little room to work. If it's too fine forget about it, it'll never stop. I think valveman has you on the right track.

Curious as to why they used a 3" grundfos pump in your well?

 

[Jeremy Harris]

Thanks again, I did some testing today and the good news is that the pressure switch always defaults to switch on until it reaches the high pressure cut off whenever the power has been off, even for a minute or two. I temporarily wired up the 1hp pump (which is the one running off the pressure switch on the pressure tank at the moment) with a time switch, and ran several tests just to be certain.

This means I can fit the time switch (a battery backed one that'll deal with power outages) so that it turns the pump off at around midnight and on again five minutes later and the pump will then run to the upper cut off, leaving the pressure tanks fully charged to 5 bar when the back flush timer comes on at 2 am. There's plenty in reserve with two 300 litre tanks, more than enough to deliver the 220 litres at over 2.5 bar that the filter needs to back flush, especially as the pump will kick in and meet around 1/3rd of the flush water requirement after a few minutes. The 5 bar initial back flush really seems to kick the filter bed up nicely, from the noise it makes, so I believe it is probably cleaning out the ferric iron particles OK.

The sand I was drawing up at high pump flow rates is really fine, as the pump is sucking it up from around 60ft below the pump. I tried a few sand filters to get rid of it, first a Rusco spin down filter with a 70 mesh screen that I imported from the US, but it went straight through that. I then tried a bigger spin down filter, a Cintropur, with a 50 micron screen, and it went straight through that, too. I ended up taking samples of the sandy water in clear wine bottles and doing a settling time test, using a stop motion camera. It takes around 2 to 3 hours for the water to clear, and I read (on here I think) that this means that the sand particles are too fine to take out with a spin down filter fitted around the pump (I had a look at these, too, as it seemed to make sense to keep the sand out of the pump).

Provided I don't pump at more than about 10 litres/minute I don't get any sand at all. I can pump all day (well, at least for 10 hours or so, which is the longest I tried) at this rate ( so around 6000 litres/~1585 US gals in total in one go) and the water stays crystal clear, with nothing settling out in my "clear wine bottle test". This is way more that we'll ever pull in a day, more than we'll pull in a week, I reckon.

The Grundfos pump was chosen because over here in England Grundfos pumps have a very good reputation for reliability, and this pump has a good reputation for being able to deal with sand, because of the "floating" impellers and ceramic bearings, supposedly. We don't have a lot of choice here when it comes to buying pumps, as so few houses have private water supplies. The people that do have wells tend to be farmers, with a high water usage and who don't want to pay the high prices for mains supplied water. The pump was expensive, but looks to be well-made, with a permanent magnet motor and some neat features, like a soft start and run-dry protection. Also, being European-made I should be able to get spares and repairs if needed fairly easily.

Thanks again for all the advice, it is great to be able to talk with people who actually know about this stuff!

 

[Reach4]

This means I can fit the time switch (a battery backed one that'll deal with power outages) so that it turns the pump off at around midnight and on again five minutes later and the pump will then run to the upper cut off, leaving the pressure tanks fully charged to 5 bar when the back flush timer comes on at 2 am.

I think the timer should be set to turn off the pump at more like 01:45 since you might use water at 01:00.

Now do you choose an electro-mechanical timer, which may be more reliable, or do you choose an electronic timer with battery backup for its clock, so that a power outage does not get you out of phase. If your filter uses an electronic timer, I would go electronic. Maybe that power outage thing is why you were giving the 2 hour leeway for your electro-mechanical timer.

Also, Grundfos makes 4 inch pumps too. Not so electronic.

 

[Jeremy Harris]

Thanks again. The filter uses an electronic timer, it's a Clack WS1 head, so an electronic timer is probably the way to go, I think. The worst case is if the timer comes on with the tanks just above the cut in pressure, when the pump will take around 15 minutes, worst case, to top them off, so I guess you're right, I should set the timer for a bit closer to 2 am, maybe with a bit of leeway for timing errors. I guess I'll have to leave both timers (the pump timer and the filter timer) on GMT (our "base" time zone) and not shift them to daylight saving time, just to make things easier. I am pretty sure the filter timer is still on GMT anyway, as I don't remember going out to the shed and changing the clock.

I didn't know about the Grundfos 4" pumps and just took the advice I was given that the SQ series was pretty much one of the most reliable pumps going. It was a lot of money for a pump, that much I do remember, and I reckoned that you basically get what you pay for. It does have the advantage of being pretty light, as I had to haul it out when I got the drillers back to try and clear the sand, and was surprised as to how easy it was to pull the pump out, It took me longer to jury-rig a frame to support the 25mm MDPE pipe so I could feed it around the house without it kinking as I pulled the pump out as it did to pull the pump out.

 

[Ballvalve]

Thanks again. The filter uses an electronic timer, it's a Clack WS1 head, so an electronic timer is probably the way to go, I think. The worst case is if the timer comes on with the tanks just above the cut in pressure, when the pump will take around 15 minutes, worst case, to top them off, so I guess you're right, I should set the timer for a bit closer to 2 am, maybe with a bit of leeway for timing errors. I guess I'll have to leave both timers (the pump timer and the filter timer) on GMT (our "base" time zone) and not shift them to daylight saving time, just to make things easier. I am pretty sure the filter timer is still on GMT anyway, as I don't remember going out to the shed and changing the clock.

I didn't know about the Grundfos 4" pumps and just took the advice I was given that the SQ series was pretty much one of the most reliable pumps going. It was a lot of money for a pump, that much I do remember, and I reckoned that you basically get what you pay for. It does have the advantage of being pretty light, as I had to haul it out when I got the drillers back to try and clear the sand, and was surprised as to how easy it was to pull the pump out, It took me longer to jury-rig a frame to support the 25mm MDPE pipe so I could feed it around the house without it kinking as I pulled the pump out as it did to pull the pump out.

You don't need the frame, just a helper or 2 to guide the pipe with. If it kinks, it's not pipe for a well.

 

[Jeremy Harris]

The snag is I was working on my own, I'm in my sixties, and I'd never done a job like this before, so I didn't want to screw up and damage something. You're right, the pipe is really hard to kink, I think, as it's thick wall stuff, and once I'd got the hang of it I could just pull it up in a big curve as far as I could in one go, tie off the pump safety line to hold it, then pull the pipe out and lay it around the house to keep it on a clean surface (the borehole is only about 15 ft from the back of the house).

Working on my own I did find it helped to have a frame to help support the pipe, I just made up a timber frame with a cross bar around 8ft up, some distance from the hole, so I could feed the pipe up and over it as I went to help it form a natural curve. It worked really well, and having done it once I'd have no qualms about pulling the pump again. The longest part of the whole process was washing down the pipe to try and limit any muck and bugs getting into the borehole, although I did chlorine shock it and pump it for a few hours, washing down the sides of the liner and the pipe with chlorine smelling water, as well as using it to disinfect all the pipe work over night, just in case any bugs got in there.

 

[Jeremy Harris]

OK,

This is a continuation of this saga, as you guys have been really helpful so far and I'd not want anyone to think that the advice given hasn't been appreciated - it has, a lot. As I've said before in this thread, expertise in this country on boreholes and wells is rare and I've not been able to get anyone to just come out and sort the problems (and I've paid a few so called "experts" who've done nothing but take my money and left me with the same problems).

Anyway, to recap, I fitted the second 300 litre pressure tank, pre-charged both to 2.5 bar and run both at 5 bar. I fitted the flow restrictor to the pipe from the pump and also fitted a timer that interrupts the pump power a short time before the backwash cycle. This always means that the tanks are at 5 bar (or just over) at the start of the backwash cycle and the pressure never drops below about 2.5 bar at any time in the cycle, so I think that the backwash is working just fine. I have no problem with drawing clean water up from the borehole and using the borehole pump alone as the water source. I even did a tough test by leaving the shower running continuously for 30 minutes last week and I still had over 3 bar left in the main tanks (and not even my wife takes a 30 minute shower - ten minutes is the max usually, whereas I'm in and out in less than 5 minutes).

I do need to tidy things up, though, as the installation isn't pretty and I'd also like to have another go at cleaning out all the packed sand in the borehole, as it doesn't sit comfortably with me knowing that the bottom 60 feet plus of my borehole is full of hard packed greensand, even if the well is working OK.

Just to give an idea of what I'm dealing with, this is a photo of the well head pit:




With the lid lifted this is what lies beneath:




There is an electrical box screwed to the wall of the concrete pit that has an armoured cable coming in (to the right of this shot) and a waterproof connector that allows the pump to be disconnected completely pretty easily (I added this, as the original electric connections weren't waterproof and looked seriously dodgy to me).




The well liner is a 125mm OD PVC pipe that at the moment has a poorly fitting 140mm ID plastic cap over it, with the pump pipe, safety rope and cable coming up out of it. It ain't pretty and is frankly a mess. There's a flow restrictor in the tee and I had a gauge on it for a while, and that air vent has since been replaced by a pressure relief valve set to 95 psi to protect the pump should the pressure get to high (after a contributor here kindly pointed out the dangers of "dead heading"" the pump accidentally). The two pipes to the right run to underground ducts, one feeds the outside tap one feeds the treatment plant in a shed on the back of the house and then to the house suppy. The pipe work in the pit isn't good, with a LOT of strain on the fittings, which is one reason I want to tidy it up.



It's hard to see, but there is a bit of perforated land drain pipe set into the tapered concrete cast base at the bottom that connects to a big soak away drain to keep the pit dry (it used to fill with rain water, as the top soil is clay).

The plan is to get rid of the pipe that feeds the outside tap and re-plumb that tap with water taken from after the iron filter. I'm going to leave the pipe there as a spare duct, maybe to feed a cable back into the house with a remote level detector or something to read out the water level in the borehole (nice to have, but way off in the future, if ever).

I've purchased a 125mm ID PVC flange fitting, that fits nicely on to the 125mm liner, and I've machined up a bit of 5mm 316 stainless plate as a cover flange, with holes drilled to take a pipe fitting for the pump pipe, a stainless eye bolt for the safety rope and a proper gland to protect the pump cable. I've drilled 6mm holes around the edge of this and drilled and tapped the thick PVC flange to take these. I've also added a stainless steel lifting eye to the top, to make pulling the thing up easier (although it's not that heavy).

I have the pump pulled out at the moment, ready to fit the new cover and connections and I'm going to have another go next week at pumping the sand from the hole with an air lift. If this works, then I may leave the air lift pipe and air pipe down the hole, but under the flange, as the small Grundfos pump will fit in there with the air lift pipe in place and it may give me a fairly quick option to just hook up the compressor now and again and suck out any more sand that gets in through the media pack and well screen.

I'll update this thread with photos of the new well head arrangement that I'm hoping will be a lot neater looking than the present arrangement. With luck I may well have pumped out all the sand at the bottom of the well by then, too!

 

[Jeremy Harris]

Thanks, I did try a few, but found that the settling time is too long for them to work. First off, I imported the Lakos sand separator, with the spin-down filter, but this just let the sand straight through the 74µ mesh with very little getting trapped, just the heavy stuff ended up in the collector at the bottom.

Next I tried a much bigger Cintripur centrifugal separator, but again the very fine sand went right through. If anyone in the UK wants either a Lakos or Cintripur centrifugal separator then they can have mine for free, as they wouldn't work for my problem. I'm sure they work very well with regular sand problems, as they both seem to have a good reputation, but they just don't work with the very fine Greensand we have.

Next up I tried filtration, but the sand would go straight through a 25µ filter and clog a 5µ filter in minutes, even the washable pleated polyester ones in the 20" Big Blue housings. One of the best companies I has advising me (and trying to sell me their spin down cyclone separator) were great, they were determined not to sell me something unless they had a good feeling that it would work. They had me do a series of settling time tests, to see how long the water took to go from dark grey to clear. I did these using clean clear glass wine bottle (it was US wine, too, a Californian Pinot Grigio that was, I have to say, a very enjoyable way of getting test containers..................).

I set up to do these settling tests with my digital camera set to take time lapse photos, with the clear bottles against a white card background. This worked great, but showed why the sand separators weren't working; the water was taking between 4 and 8 hours to settle clear, so the particle size and mass was just too small and light for the centrifugal systems to work, I have to give it to the guy trying to sell me the expensive spin down cyclone system, as soon as he saw the results he said right off his product wouldn't work and he had doubts that any spin-down filter would work.

I then got my drillers back in to try and clear the sand from the hole. I won't go into details, but they were nice guys and their attempt to pump the fine sand from my borehole (there's around 20m of it packed in the bottom) failed, for several reasons, not least of which was (putting it politely) their rig was crap. I've now read up on sand lifters from loads of useful web sites (all in the USA for some reason - you guys over there dominate the world in well technology you know!) , and made my own - it's getting tested out next week - wish me luck!

Next up in my train of experiments was a two tank set up, where I pumped from the borehole to a 650 litre tank fitted with a float switch, then pumped from about 1/3rd of the way up the 650 litre tank with another pump to feed the house. At the same time I fitted a venturi air injector to the feed from the borehole, that restricted the flow but helped oxidise the iron and drive out the smelly hydrogen sulphide. This worked well, but could only be temporary as I have no room for the second tank and had to stand it on the back path whilst I was using this set up, where it got in the way.

I learned several things from doing this. Pumping at full rate (without the air injector venturi fitted) filled the tank with cloudy water with loads of sand in it, and it never got long enough to settle before it'd get drawn into the second pump and iron filter. Fitting the venturi fixed this, by throttling back the pump flow. I found (after loads of experiments, moving the pump up and down the hole, changing the flow rate by throttling the pump with a valve etc, that with the pump 25m down the hole and a flow rate of not more than 10 litres/minute I ALWAYS got crystal clear water. I've been treating these as magic numbers, as I can pump all day (literally, I've just left the tap running all day) at 10 l/m and the water is always clear. with no sand or sediment at all.

Another thing I learned is that air injection works exceptionally well at getting rid of both iron and hydrogen sulphide. Furthermore, when I added a home made ozone generator to the venturi air feed the results were outstanding, the oxidation was very rapid indeed, such that the clear section of PVC I fitted straight after the venturi went brown with rust within a few hours. The taste of the water improved massively too, it really was the best water I've had out of a tap in a house (not saying much, though, as our municipal water supplies are often highly chlorinated and taste awful).

So now I had learned a lot of useful stuff:

1: I have a LOT of very fine (between 5µ and 20µ) Greensand that gets through my glass media pack, though the slotted liner and through a packed layer of (I guess) coarser sand that is covering all of the slotted lined screen section. There are no gaps in the liner; it's screwed together sections of 125mm PVC and I've had a video camera survey, and all is nice and clean and tidy until the packed sand layer at about 45m down a 65m deep borehole.

2. The fine sand takes 4 to 8 hours to settle out, and so centrifugal sand separators don't work and I don;t have the space for staged settlement tanks (I did sort of consider it, as a sort of garden feature, but She Who Must Be Obeyed said NO.................).

3. Conventional filters clog too quickly. It even clogs the mixed media sand and Aquamandix iron filter I have within an hour or two, slowing the flow rate right down until I back wash it (luckily the stuff is fine enough to backwash out OK).

4. Oxidation works really well at cleaning up the hydrogen sulphide and iron problem and adding a bit of ozone makes a massive difference to the effectiveness of this.

5. Keeping the borehole water flow rate down below 10 l/m means I always draw clean water. To get enough to backwash the iron filter I've fitted two 300 litre pressure tanks, charged to 5 bar with a 4 bar pump cut in pressure and a 2.5 bar pre charge. This works well, I get enough backwash water from the tanks and just have to make sure they are fully charged before the backwash. This I do with a simple time switch that turns the pump pressure switch power off for five minutes half an hour before the timer backwashes the iron filter. Turning the power off and on again like this triggers the pressure switch to always turn the pump on until the 5 bar cut off is reached.

So, I have a system that works, but is a mess. I don't know about you guys, but that well head looks like a right bodge job to me, and the well needs a proper cover and the pipework tidied up. That's one thing planned to do next week, with luck.

I also want to aerate the water as I used to do with the two tank system, as it did make the water taste a lot better. I'd like to pump air is at the flow restrictor at the well head, and maybe look at adding ozone injection there too. I couldn't buy one of the air tanks you can get over there in the US, so I made one. I managed to buy a straight 1054 tank with fittings, screen and riser and have adapted it to take an air bleed line, using a length of 8mm pipe fed down through a pressure gauge fitting (1/4" BSP) to around 18" below the top. I've fitted a bottle type air vent to this (with a 10 bar rating) and I've tested it and it seems to work. If aerated water fills the tank the bottle vent lets the excess out until the level of the bottom of the pipe. This works a treat and allows me to take a feed from the pump, restricted to 10 litres/minute maximum, with air (or later ozone) bubbled in to it. The excess smell air comes out of the bottle vent and the water goes on to the filtration system.

It's a work in progress, but I'm learning a lot, hopefully passing some of that learning on to others here in the UK who are, like me, finding it hard to talk to trustworthy people who know their stuff, and all because some of you guys are helpful enough to offer advice and criticism which is really appreciated. Thank you all for your help so far - you can have no idea how important it is to have comments from people who know what they are talking about. If I had the money I'd import one of you experts over here for advice, feed you up on local food and beer and take you to see some of the interesting stuff around, like Stonehenge just up the road a few miles, or the Roman baths at Bath, that are still working today 2000 years on (now that's a good bit of water engineering!)

 

[Jeremy Harris]

I guess you're spot on - all sand is not equal!

We were warned that our aquifer was "running Greensand" at a depth of around 40 to 50m. The hydrologist was spot on and put a small note reminding the drillers to not fit a geofabric sock over the slotted liner screen section (here it is normal practice with our more normal chalk drilled wells to fit a sock over the screen as a filter), as it might clog and reduce yield. I now know exactly why he wrote this comment, but just didn't realise how significant it was at the time. With hindsight I should have asked the hydro geologist more, as I'd then have probably chosen a different drilling company and may not have run into so many problems.

On the down side, I'd not have learned as much about a load of realjy interesting (to me) well stuff!

 

[Jeremy Harris]

I'm sure this thread is as boring as hell to you guys, but what I'm doing over here is really exciting to me and very educational, as I'm finally, after a year of struggling, getting to grips with the problems with this well. I am now more than convinced that I've had very bad advice from people over here right from the off. Some of you guys could make a killing if you moved over this side of the Atlantic and started offering your really professional services - trust me, there is a big gap in the market here!

Today I tried my home made air lifter to see if I could get some of the sand out that the drillers failed to shift. Now, to re-cap, this well was supposedly bored to 65m and lined to that depth with 125mm diameter PVC liner, with a 15 m slotted section at the base, with crushed glass filter pack around the hole (which was bored to 200mm (~8inch) and the top 20 to 30m or so packed around bentonite to give a sanitary seal from surface run off.

Last time we tried to air lift the well the guys got to 45m down and hit packed sand, which their bodged up air lifter (bits of 25mm pipe and a bit of bent over PVC tube run off a mother fucker compressor towed behind a big truck). After three house they didn't get anywhere, I p[aid them a few hundred dollar equivalent for coming out and sent them home.

Since then I did some reading up and made my own air lifter pipe. I used a piece of 28mm copper pipe (around 1 1/8") and cut an angle on the end, with the sharp edges bent in a bit so they didn't catch on the joints in the liner (the liner is threaded together). I brazed in an U shaped air line out of 8mm copper pipe (around 5/16" diameter) and brazed on a 3/4" BSP fitting do I could screw this to a longer lift pipe. Here are some shots for those bored enough to want to see some pictures by now (this must be every day stuff to to you guys!):

This is the sharp, business end of the air lifter, with the sharpest pits bent in a bit to they didn't snag the joints in the liner. I wanted something sharp, so I could penetrate the hard packed sand that's sat at 45m down (yell if you want this in feet, it's getting tedious doing all the conversions). A few inches up from the end I drilled a hole and brazed in a U shaped bit of 8mm copper pipe, to the pipe is more or less in the centre of the lifter pipe, facing upwards, but with a connection on the outside for 5/16" bore air hose ( brazed a pipe olive over the end of the pipe to give the hose something to grip on):




Close up of the brazed in air pipe:



I chucked this down the borehole and when I hit sand I turned on the air. Sure enough water and sand gulped out the end. Now, I was using a small 1 1/2hp shop compressor, set to around 80 psi to get enough air to overcome the head of water. Two lessons here. The first is more air is NOT a good thing. You try a little bit of air and think, well, a little works OK, so more should work better, right? NO. What happens is that your air lifter turns into a wild animal, and forces itself out of the borehole. You experienced guys are probably killing yourself laughing now, but trust me, when you're torn between getting to the compressor to turn the power off or trying to force 40 odd metres of pipe back down a hole against its will, and you're on your own, it is not a joke.......................

Suffice to say that there is NO way you can force the pipe back down the hole with even a puny little 1 1/2 hp shop compressor set to around 80 psi feeding it. You have to turn the air off, then push the pipe back down, then GENTLY turn a LITTLE bit of air back on. I was amazed at how little air the thing needed to work. Set to optimum it would gulp out sandy water, like this:






Which was just about perfect. The compressor would only fire up every 10 minutes or so, that's how little air it was using.

I pushed the pipe down, wiggled it too and fro and rotated it in the bore, and in the space of an hour or so I had got the packed sand depth down from 45m to about 55m, so a lot of sand has been shifted. When I left this evening the pipe felt like it had bottomed out, so I'm going to chuck a camera down tomorrow and see what's at the bottom. I have a strong suspicion the lined hole ends at 55m, not 65m as in the spec, as it feels very much as if the pipe is now hitting the plastic end fitting.

I'll mod the copper part tomorrow too, to add an extra length of slightly smaller diameter copper pipe at the bottom, to maybe get a bit more lift and clean the hole right out.

The tech specs for this aren't great, it's a 100m roll of 25mm MDPE water pipe (so around 1" OD, maybe just over 3/4" ID and around 300ft long) that I left full length on the roll. The air hose is that standard 5/16" nylon reinforced stuff use for tool air lines. I bought a 100m (roughly 300 ft) roll and didn't cut it, just used the whole length. The length of copper pipe is around a metre (say three feet) with the brazed U bend air pipe around a foot up from the end. It has a 3/4" threaded and brazed on and that fits to an MDPE fitting.

The device is a bit Heath Robinson, but extremely effective. I reckon that given another hour or two tomorrow the borehole will be as clean as a whistle.

Some have asked about the very fine Greensand that makes up our aquifer and causes the problems. Here are some photos, not too great, that show the wet stuff on the boards where I was discharging the hose and also some coarser dry stuff on the ground from a previous clean out attempt:





Tomorrow I hope to be done with clearing the borehole out and am hoping that with the pump set at around 20m down (lowest ever pumped level has been about 12m down, and that was when pumping at the max the pump could run at, in excess off 2000 litres per hour, which is way more than we ever need. Normal rest water level varies between 3.5m down and 4.5m down, although the hole did go artesian last Christmas when all the local aquifers saturated after days of heavy rain (one reason I'd like to have a bolted flange on top of the head - should have one later this week with luck.

If this gets too dull, just tell me to shut up and go away!