Submersible Pump:Noobie questions

[Keithwl]

Hi, All.
I have a well which was originally badly 'outfitted', (not me!), and now I need to improve it.
The well is a cased bore 16cms diameter, and is about 75 feet deep. The water has then to be pumped uphill to the house through a vertical distance of about 50 feet. (the actual pipe run is about 350 feet). The original installation was a deep well pump, with a pressure tank fitted at the head of the well. In general, when it was working, it was reasonably good, but had a number of problems. This all came to a head a few days ago when we found the cast iron pump housing had frozen, resulting in a large crack.
I have been considering changing to a submersible pump for a long time, but have no experience of them, so maybe I can get some help here please?
1) What size pump do I need for the above well, or how do I calculate what I need - flow rate is not an issue, because the water can be pumped slowly to a reservoir tank before use - ie the water is not used 'online'
2) I have read a lot of conflicting information about torque arrestors and/or spiders, ranging from 'definitely fit this' to 'never fit this', often no reason given. What should I do?
3) I would like to keep the existing system after the pressure tank - in other words, simply fit a pipe down the well with the sub pump on the end - any reasons why not?
Thanks.

 

[Reach4]

Nice big casing.

Presuming the well is set at about 65 to 55 feet. So figure the pump to be pumping up about 50+50 ft from the water surface vertically, for about 100 ft of head. The 350 ft of 1 inch pipe or bigger will not be a big drop.

Why cannot the water be used on line? The answer must be that the well goes dry. Otherwise, you are are better with the water online rather than stored.

Online, the pressure tank can be at the house or at the well. With the tank at the house, pressure regulation with different flows will be better. However the pressure switch needs to be at the pressure tank.

Stored, no pressure tank needed for the submersible. Then there is a float switch at the storage.

If you don't want to run wires to the storage tank, you can use a pressure switch and pressure tank near the pump, and have a float-controlled valve at the storage.

The smallest common submersible pump motor is 1/2 HP. A 7 gpm 1/2 hp pump would be good for direct where the pump also provides the pressure for the house. For indirect, maybe 10 to 16 gpm 1/2 hp.

The only check valve (one-way valve) should be at the pump. You can have one just above the pump and/or in the pump.

Regarding torque arrestors, keep reading. Your well is big, so maybe you could have one as a bumper without extending out to the casing.

You would like to have a "flow inducer" (sleeve). With your 1/2 HP motor it may not be needed, but it is best. It is cheap.

 

[Sponsor]

 

[Valveman]

That 50' of lift is costing you about 21 PSI loss. So to get 40/60 at the house, the pump needs to be working at 60/80. You will probably need a submersible pump, as most jet pumps cannot build that much pressure. If you install a pump that can do 60/80 and the well can make enough water to supply the house, then you don't need to go to a storage tank and booster pump.

But if the well is a weak producer, a storage tank or cistern with a booster pump is a good idea. Even then you can use a submersible in the cistern to be able to build the extra 21 PSI needed to work at 60/80 pressure.

 

[Keithwl]

Reach4 and Valveman:
Much useful information, for which I thank you.
Your answers have also told me that (in my ignorance), I probably omitted some information.
Original pump was a jet pump when we got the house. The first one failed (bearing and seal) some time ago, and due to other pressures, I replaced the pump with an identical unit. It has never been really satisfactory, for a number of reasons.

The water level is subject to quite a wide variation. At times the water level rises to within about two metres of the surface, and at other can fall until there is maybe only 4 meters of water in the well. The well has intersected a supply of water which lies below 8 metres of soil, then 12 metres of solid rock. It is not high volume, but does seem constant. I believe we are also getting some seepage into the well due to surface water, because the well is at the foot of a hill - the water is pumped up about 50 ft to the house at the top of the hill. I think this seepage is causing the fluctuation in height, because late in the year we get very heavy rainstorms, but then can go from May to October with virtually no rain, and temperatures of 40°C+. It appears that the original reason for not using the water online is that the reservoir supplies water when the well is very low, or during our (frequent) extended power cuts - this is a small village in the back of beyond in eastern Romania!

At present, the water is pumped to an 'interim' tank on the ground floor of the house, and then using a small centrifugal pump it is pumped up to a 1000 litre reservoir tank in the roof. I believe this was done because originally the well pump was not able to get the water to the roof tank in one lift. This transfer is automatic using float switches, and works reliably, so I am happy to leave it in place. Internal house pressure is no problem, and is handled by a small 'on-demand' pump to provide good pressure from the reservoir.

The pump at the well was originally controlled by a float switch in the 'interim' tank, and its pressure by a mechanical pressure switch.
When we first moved there, I found the mechanical switch was unreliable. A change had no effect, so I built a PIC microcontroller unit which uses electronic pressure switches to detect high and low pressures. After a bit of software tuning, this has worked well, and it also has a facility for detecting excess pump runtime, preventing more pump damage if there is no water in the system. My intention is (was?) to use it on the new system, depending on what I decided to install. Incidentally, it would be a lot of work to run wiring from the house to the well - about 350 feet of trench digging through rocky ground. (Maybe the wife could do it for fun......)

However, the jet pump itself is a damn nuisance. It needs priming (on several occasions it has lost suction due to water level fluctuations, and I cannot extend the tailpipe any lower, because of picking up dirt, and the priming process is a pig in itself. The pressure tank needs re-pressurising every 6 months (I was told) otherwise it no longer works as pressure tank, and the motor cycles on and off repeatedly. I had to pull the pipes once to replace a broken filter/check valve at the bottom of the pipes, and that was no joke - the connections to the pump gave me 'a lot' of trouble, partly due to limited space at the well head.

So the intention, after Jack Frost ruined the jet pump, and reading all I could find online was to fit a submersible pump. I can get the pipes below the frost level with a bit of work, and I can easily obtain a subpump, but wasn't sure what size - they are available here from about 1/2 HP to anything I can afford to pay. I have found one which is 1.5HP, and capable of 250 feet (80metres) head. (but the tech data shows delivery rate is 0 litres/Min at 80 metres!). I estimate I have to lift an average of 35 feet from the well, then 50 feet up the hill, so this pump seems more than adequate - I may eventually then be able to do away with the 'interim' tank - but I was interested to know how to determine what I actually needed - obviously bigger pumps cost more, and I ain't a millionaire!
SO thanks for your information - Its given me something to think about, and now I know where I can get well-informed help - sometimes the internet can be pretty misleading when you are feeling your way.

 

[Reach4]

1.5 HP is silly. Why not pick 1/2 HP, even if it costs a little more?

 

[Valveman]

You won't be able to get a submersible as deep as a foot valve, and sucking up dirt will still be an issue. But a 1/2HP, 10 GPM sub would do what you want.

 

[Keithwl]

Thanks, Guys - this is just what I wanted to know. I mentioned the 1.5HP pump because I was offered one at a good price, but I had no idea what was needed or correct, so I'll take your advice - thanks again.
I put the water through a sediment filter now to clean it a bit, and I guess I will keep that. It appears to be like very fine sand, or more like dust, but its an aesthetic thing - I had the water tested, and it is clean and fit for drinking (no chemicals here up in the woods!), but it makes the water look a bit discolored.

 

[Keithwl]

Just wanted to say thanks to you guys for the advice. The system is up and running now, and I am busy kicking my own backside for not fitting a subpump long ago. I eventually fitted a 1HP pump, simply because it was the best available at the price. I noted the suggestion that a pressure tank was not necessary with our stored water system, but in the end, I left the tank from the original system in place - just 'cos it was already there.
A small issue did come up, which I think I have resolved. As you guessed, it is possible to pump the well dry, because we get very long dry summers, and the ground water drops quite seriously. On the original system, this meant the deep well jet pump ran dry, because it had no system to stop it in the event of no water, and I had to replace the seals in the pump twice. I experimented with depth sensing to stop the motor if no water, but never really got a decent system up and running- I ruled out sensing 'electrodes' in the water due to connection and corrosion problems, and experiments with a closed pipe and a pressure sensor at the top were not satisfactory. It was also difficult to calibrate with any accuracy - temperature had a bad effect. In the end, I put a timing loop in the pump control software.

The original system operating pressures were set up so that it pumped up to about 6 bar, then the motor cut off, and water flow was maintained by the pressure tank down to about 3.5 bar, at which point the pump was switched back on. This meant the pump was cycling on and off, with on and off times of roughly 3 minutes. This proved to work reasonably well: It usually needed to run about once or twice a day, and the pump cycled on maybe 10 times at each occurrence. Not perfect, I know, but it worked. Because of this cycling, I was able to put a timing loop in the software which was just longer than the 'ON' part of the on-off cycle. This timer was reset every time the pump started. If the water ran low, then the pump could not get to pressure (6 bar), so continued running - the timer timed out, and cut off the pump after a few seconds more than the normal run time - it had to be manually reset, to prevent it trying to run again and damaging the seals by running dry - no big problem.

The duty cycle for the subpump is S1, or continuous if the temperature was not exceeded, so theoretically I could just let it run, but I still had the problem of possible low water. The obvious solution was to adopt the same timer solution. This meant I could use the computer control system virtually unchanged. All I found I had to do was to reduce the maximum pressure it reached - It was only necessary to set it to about 4.5 bar. This was because of the time that the pump took to reach this pressure, else I had to change the software (again!). So now it cycles on-off between about 3 bar and 4.5 bar, and is protected against running dry.

I intend to 'fine-tune' it when I get time. I think it could happily cycle between 3.5 and 6 bar, but because it takes longer to reach the high pressure than the timer runs, I will also need to alter the timer software. This should reduce the number of times the pump cycles on-off, with consequent less wear, I guess. But thats for later - as they say - so much to do and so little time.

Thanks again for your advice - useful and to the point.

 

[Valveman]

One of these would make your life much easier.

 

[Keithwl]

Interesting info, Valveman, but could I respectfully suggest you consider life in rural Romania - I lost several items through our customs refusing to release it because 'its illegal here' - you have to experience Romanian bureaucracy to really appreciate it . Not only that, it it perfectly possible to have to make several trips to the main customs office in Arad to actually (maybe) get your own property. Arad is only 25 kms from where I live, but the traffic and driving is so bad, it can easily take 5 hours to get there and back - I know... don't ask me why I live here. Officialdom here has not progressed in the 25 years since they shot Ceacescu.
I did find a similar device that was made in Germany on sale here in Romania, but it cost the earth and half the moon - I built a similar unit using a PIC16F84A for the equivalent of about 5 dollars and 5 hours work, and it does seem to work OK, so I'll be content with that. Its unfortunately a fact of life that many things which you guys in the States can get easily and take for granted, are not available or are bl**dy expensive in Europe, so making it is often the best option.
All the best.

 

[Valveman]

Sorry for your problems. You are doing very good with what you have available. It is just much easier and more reliable to do dry run protection with low amps instead of time.

 

[Keithwl]

Hi, Valveman,
When I was messing about with the protection system, it did cross my mind that maybe the pump motor would take less current with no water (no load), but I couldn't find an easy way to install a method to monitor the current. I know there is the 'classic' way of voltage drop across a resistor in series with the motor, and it also occurred to me that if I was measuring current, I could in effect build a 'window detector' - sense the current within a 'normal' operating range, and that way I could protect the motor against both 'underload' and overload. However, after messing around with it for a while, I decided it would not be easily practical. I could fit a resistor in series at the controller I had built, because this has a connector to provide power to the motor, but I already had the controller (with the timer), and since we had no water without the pump, I decided to use what I had. However, its gone on the pile as a possibility when I have more time to get a 'roundtuit'. Thanks for the suggestion.
I'm beginning to think I should go into business here. Its 2019, Romania is (allegedly) a reasonably modern European country (more than 25 years since they shot the last dictator), the village has maybe 1000 people, but we have no piped water, no mains drainage, no form of heating other than wood (and since we are surrounded by a huge oak and ash forest, the major industry here is wholesale uncontrolled log theft - they get about 800 euros for a single oak log 6 metres long, which they steal for free). The only modern thing which seems to work is our broadband connection, but I did notice the last storm left branches hanging on the cable.
As far as I know, I am the only person in the place to have gone to the trouble of fitting a pump to provide water to the house, and a modern plumbing system - everyone else trots down to their well with a bucket. Its not uncommon to see the proverbial little old East European lady, who looks as though she is 70 years old, but is really only 45, trundling down the road with a bucket swinging from each arm. Most of the wells are hand-dug open stone-lined wells collecting rainwater and groundwater, they do not tap into any aquifers, so they are usually dirty. We were lucky to find a piece of land with the drilled and cased well into the aquifer - apparently someone had grand plans to start a horse-riding school, but underestimated his costs. Some families have an income which only amounts to about 100 dollars a month, or less - the joys of the old communist government!
The European Union has reputedly paid to lay new roads and provide the other necessities, but the cash has all been embezzled by local and regional politicians....and of course, once the EU has allocated the cash, it has no follow-up to check on correct usage, etc. I know, why the hell do I live here? The local wine and food is good, the weather is wonderful, cost of living is cheap (important when you have a fixed pension) - I'm happy, at least I have something to moan about
All the best.