Pump Sizing Advide, Deep Well, High Water Level

[lightnb]

Looking for some advice on a new well pump install.

The current water depth (using a fishing bobber) is about 40' down from the surface. The well itself is somewhere between 340-360ft deep. There's 6" diameter casing for the first 60' until it hits bedrock. Then there's no casing, just rock the rest of the way.

This is new construction, so I don't have any way to test the refill rate, although I think the driller said it was at least 5GPM refill.

If a 6" well is 1.5 Gallons Per Foot (got that figure online somewhere), then water at 40' and a 340' depth would mean 300' x 1.5 = 450 gallons in the shaft. At 10GPM, that would run continuously for 45 minutes without any refill factor, if the pump were near the bottom.

For two people, I can't imagine using that much water at a time. A washing machine and a shower (there's only one shower and one bathroom right now, but I might add (at some point) another toilet+sink (no shower or tub) so guests don't have to use ours.

I also plan to do some gardening and will need water to fill a pond (if rain is insufficient) and for irrigation. But that seems more like low-flow over a longer time. For example, a hose bib left on for a few hours.

I'm thinking I should get the biggest pressure tank I can, maybe something in the 80 gallon range, to minimize pump cycles. An 80 gallon tank could supply a 30 minute shower with a 2.5 GPM head with only one pump start. A 10 GPM pump would then run for 8 minutes to refill the tank before shutting off. (I'm sure that math isn't quite right... because it's based on pressure, not on the tank being empty, but I think you get the jist of it).

An 8 minute run of a 10GPM pump would draw down ~55 feet of depth, reducing the water level to about 95' from the surface.

Except, with 5GPM back-filling, 40 gallons would come back in during that 8 minute draw, replacing 26 feet. So it would be 70' to water level after the completed pump cycle.

So: How stupid would it be to set the pump at 150ft? 200ft? And not 340ft?

And: If the refresh rate is 5GPM, is there a reason to do a 10GPM pump?

I also want to do a hand pump because I'm in a rural area where the power company takes it's time restoring after a storm. ie. seven days. So I was looking at the Bison, because it works inline and can refill your pressure tank. So you could hand pump the tank full then take a shower.

Friction loss: Is this calculated horizontally from the well head to the pressure tank, if the pressure tank is right next to the well head? Or should the line to the house (after the pressure tank) be factored in?

I feel like I'm going in circles with the horse power, depth, and GPM ratings. Not sure what size to use.

It looks like a Franklin Series V "7GPM" 1HP can do 9GPH @ 50PSI @ 100ft water depth. If I'm reading the table correctly. And I assume that means if it's 100' to water, no matter how deep the pump is.

But I'm not sure what depth to set it at, vs HP, vs GPM rating. Any recommendations?

 

[Bannerman]

Assuming you are intending the common 40/60 psi pressure switch range, an 80-gallon pressure tank will effectively contain 0-gallons @ 40 psi, and approx 20-gallons @ 60 psi.

Unless the water consumption rate matches the pump delivery rate, the pump will continue to cycle. For instance. if water is consumed at 3 GPM for a shower, a 10 GPM pump will then deliver 3 GPM to the shower and the remaining 7 GPM will refill the pressure tank. With a 7 GPM pump, 4 GPM will be refilling the pressure tank.

Once the pressure switch senses 60 psi, the pump will be shut down so any further water use will cause the system pressure to drop to 40 psi whereby the pump will be again activated. You shower pressure will continually be either rising from 40-60 or dropping from 60-40 psi.

You may want to consider a Cycle Stop Valve. https://cyclestopvalves.com/

Not only will a CSV prevent either capacity pump from cycling so long as more than 1 GPM is being consumed, but the pressure will also remain consistent at 50 psi. Because the pressure tank will be restricted from filling faster than 1 GPM, a 4.4-gallon pressure tank will be typically all that will be necessary.

Forum Moderator Valveman is the inventor and manufacturer so you may wish to direct questions to him after reviewing the info and videos included on that website.

 

[Sponsor]

 

[Valveman]

Thanks Bannerman! It is a common mistake to think an 80 gallon pressure tank holds 80 gallons of water, when about 20 gallons is all it can actually hold. So, you would need four of those 80 gallon tanks to get the run time and draw down you are figuring. I don't see any reason to set the pump at the bottom of the well. You would need a really deep set pump, that would be working to lift water from only 40' most of the time. This causes upthrust on the pump and is not good. You would have to use a flow limiting device like a Dole valve to keep the pump out of upthrust when the water level is high. Because, no matter how deep a pump is set, it is only lifting from the water level.

The average home only uses 300 gallons per day. At 1.5 gallons per foot you would only need about 200' of submergence. That would mean setting the pump at about 250'. However, for irrigating and filling a pond it would be good to know from what level the 5 GPM refill rate is coming from? You may need to set the pump at the bottom to access all the water you can get.

Pressure tanks are not made to store water. Your water is stored in the well and supplied by the pump. The only purpose of a pressure tank is to limit the number of on/off cycles on the pump, and when you have a Cycle Stop Valve to do that for you, a small pressure tank is all that is needed. A 10 GPM pump can pump as much as 17 GPM. But the CSV will turn that pump into a variable flow pump that can supply from 1 GPM to 16 GPM, matching the amount being used at the time. So even with a 10 GPM pump, you can safely use 5 GPM for sprinklers and irrigation without cycling the pump to death. I would use a 10GS10 Goulds or a 10S10-15 Grundfos set at about 340'. Then I would install a 15 GPM dole valve and a PK1A control kit with a 10 gallon size tank and a 50/70 pressure switch. In this way you can use water anyway you want and have a strong constant 60 PSI while doing so.

 

[Reach4]

I also want to do a hand pump because I'm in a rural area where the power company takes it's time restoring after a storm. ie. seven days. So I was looking at the Bison, because it works inline and can refill your pressure tank. So you could hand pump the tank full then take a shower.

Also look at Simple Pump. https://www.simplepump.com/

 

[Valveman]

Hand pumps are great to get a few buckets of water. But hand pump enough into a pressure tank to take a shower and you will really need that shower. Lol! Better get a generator.

 

[lightnb]

Hand pumps are great to get a few buckets of water. But hand pump enough into a pressure tank to take a shower and you will really need that shower. Lol! Better get a generator.

In certain types of situations, gas may not always be available. I can live without showering, but I can't live without drinking, so having something that can at least draw enough to drink is important.

Also look at Simple Pump. https://www.simplepump.com/

I'd read about them too a few years ago, but forgotten the name. Thanks for reminding me.

it would be good to know from what level the 5 GPM refill rate is coming from?

There was very low flow until they got to the bottom. My understanding from neighbors is that there is an aquifer (like an underground river) running through the bedrock that is about ten miles wide. And when you drill deep enough into the bedrock, that underground river, which I assume is under some sort of pressure, forces the water up the shaft. But not a geyser.

You may want to consider a Cycle Stop Valve. https://cyclestopvalves.com/

I've seen them mentioned in other places but with some controversy. Just watched the video, but it doesn't explain how it works. ie. does it drop the voltage to the pump, like a (designed-for-motor) dimmer switch? Does dropping the voltage void the mfg warranty?

I've also seem some pumps that have an electronic control box at the top of the shaft (usually in a shed of some kind). Is that similar? Or an alternative?

So it's sounding like the best pump size would be one where it runs continuously at the desired pressure and flow rate. So if I needed 2.5 GPM continuously, a 2.5 GPM pump would be best because it would start and keep running.

Is it ever advisable to size the pump based on intended usage, not on the house? ie. If two "old people" live in a 3/3 but don't have kids anymore, you would size the pump for just one bathroom because that's all you really use?

I'm also the kind of person that is consciousness about things going on at once. So, Just because I have a dishwasher and a washing machine and a shower, doesn't mean I would ever run them all at once. I might run the washer/DW at the same time on "cleaning day". But usually time my shower around the washer so not to use both at once.

I don't know what a residential hose bib uses, but assuming it is about 2.5GPM, then it seems a 2.5GPM@50PSI continuous pump is hat we would want for irrigation with one sprinkler (set) or a pond filler. (Pond/aquarium filling usually is done very slowly because deep well water usually has low oxygen and too much at once will crash oxygen levels and kill fish. Ponds are larger bodies, but I always use just a trickle on an aquarium, run over several hours.

 

[Bannerman]

The video Valveman included is only one of the videos included on the CSV website.

A CSV is a fully mechanical valve which will limit and regulate the water flow from the pump. No electrical adjustments are made so the pump will continue to operate full speed but will consume less electricity while less water is flowing as it will be doing less actual work.

In using a CSV, you won't need to worry as much about pump size as the flow rate from the pump will be variable and will be always equal to the flow rate being consumed. If only 2.5 GPM is consumed for a shower, the pump will deliver 2.5 GPM. If someone turns on the washing machine that requires 5 GPM while the shower is running, the CSV will immediately increase the flow to 7.5 GPM from your 10 or 17 GPM pump, while continuing to deliver consistent 60 psi pressure as Valveman suggested.

A CSV drastically changes the way a well pump will deliver water. Any controversy is usually from people including most pump installers who don't understand how a CSV works.

 

[lightnb]

What are your thoughts on roll pipe vs sticks?

Do you ever use an aircraft cable/"wire rope" as a safety/lift cable on the pump so you aren't lifting the pump by the pipe and electrical cord?

 

[lightnb]

The driller said his records said it was a very high refresh rate, like 30 GPM and "not likely" ground water. So we should be able to set the pump higher like at 200'? Any reason to go lower than that? That's 225 gallons in the shaft (above the pumping height) and a refill rate faster than a 10GPM pump.

Also, is this suitable as a lowering/safety cable:
https://www.amazon.com/Stainless-Ai...485702011&s=industrial&sr=1-18&ts_id=16413891

 

[Reach4]

The driller said his records said it was a very high refresh rate, like 30 GPM and "not likely" ground water. So we should be able to set the pump higher like at 200'? Any reason to go lower than that? That's 225 gallons in the shaft (above the pumping height) and a refill rate faster than a 10GPM pump.

Probably not. Use a flow inducer sleeve. One of the things that will do is keep you from pumping right against a loose stratum.

Don't use a safety cable, because it can get you into trouble.

Also, is this suitable as a lowering/safety cable:

No cable is better. I did not look at your link.

I am not a pro.

What are your thoughts on roll pipe vs sticks?

SIDR polyethylene is good if you are not using a hoist. Ideally use 2 extra-long barbs with 3 worm gear clamps each. Tighten to 5 ft-lb (60 in-lb).

If you are a pro with a hoist truck, PVC is better.