Well pump struggling to reach cut-off

[hamm107]

I don't know the specs on my pump, but we are in Maine with a drilled well, probably around 200' with a submersible pump that probably puts out less than 5gmp. It is a residential set-up, but we also grow about 1.5 acres of vegetables which have some drip irrigation and some sprinkler units. The pump is likely at least 15 years old and it's been used pretty hard.

We run a set of sprinklers that uses about 5gpm total. They will run fine, but get a little weaker after 20 minutes, but still will run as long as we want to leave them on at that slightly weaker flowrate. The pressure at the tank will sit around 30psi the entire time they are running. However, after we run them for a couple of hours, the pressure will very slowly rise from 30... it could take an hour to reach 50 and shut the pump off with nothing running. We have not lost water yet. If I shut off all water inside and outside and shut off the pump breaker, the system does appear to hold its pressure, so I'm guessing no leak. If we never lose water, I'm guessing we're not running the well low/dry, but I don't know if that's an accurate assumption. I do think that the pressure gauge and switch are not clogged and are reading accurately because the switch does open when the pressure gets to +-50. I haven't checked the pressure tank air pressure with the tank empty, but I believe that would help if we were cycling a lot, not the opposite where the pump just keeps running and takes forever to get to 50.

Would love some insight if anybody has some thoughts to offer. Thanks

 

[Valveman]

Sounds like you are still pumping the well off. If you are trying to use 5 GPM but but the well is only supplying 4 GPM, the pump will just do what it can with what it is getting. It is not good for the pump to run this way. If you run one sprinkler at a time instead of two the pump will probably cycle on and off, which also isn't good for the pump. Test how much is coming out of the sprinklers when it has run at 30 PSI for a while. Then adjust your sprinklers to use about 1 GPM less than that amount. If the pump cycles on and off at this flow rate you can restrict the pump with a ball valve before the pressure tank, or add a Cycle Stop Valve to restrict the pump automatically as needed.

 

[hamm107]

I have also recently noticed that even after laundry or a shower, once it is off just like the irrigation, the pressure takes a very long time to reach cut-off. I will let it sit for a couple of hours and I will pay attention to how fast it gets to cut-off if I only use a little water, like just enough to get it to 30 psi for the pump to turn on.

I can try reduce the sprinklers and drip systems to better match the well. When I said the pump puts out about 4gmp that's just from it filling a bucket with about 4 gallons in a minute... I have no idea what the well refill rate is from the aquifer.

If I am running the well down, does it make sense that I would still have constant flow, consistent pressure around 30psi, and then when water is shut off, that it can take over an hour to reach cut-off? Is the theory that the pump is just pumping the water that is flowing in from the ground at this point, not the reserve that is in the well, because I have drained that pretty quickly? If that were the case, once everything is shut off, shouldn't it still be able to reach pressure pretty fast and the pump would shut off? I don't think it would take too much water to just pressurize the line to the pressure tank from the pump at the bottom of the well (which should be completely full because we never lost water)? Thanks,

 

[Valveman]

Yeah check and see how fast it fills the tank after the well has rested for a while and had time to recover. Should fill the tank in a minute or two. Like I said it is not good to run a pump that way, and you may have damaged the pump until that is all it can make.

A good pump in a weak well will pump good water for a short time and drop off suddenly. A bad pump working in a good or weak well will start out pumping slow and take forever to fill the tank.

 

[hamm107]

So after I let the well rest for a few hours I ran a faucet to bring the pressure down to 30 and turn the pump on (maybe 2 minutes). Once the pump kicked on I shut the faucet off and watched the gauge and switch... it hit 50 and shut off in probably 30 seconds.

What do you think that means?

Likely the pump is fine and we are drawing the well down too far when we use larger amounts of water? And after we use a lot of water and draw the well down, the pump is only pumping the water that is refilling the well through the ground/aquifer, and is probably cavitating some and sucking some air, but there is enough water flowing into the well to keep a steady flow and roughly 30 psi up top?

 

[Valveman]

So after I let the well rest for a few hours I ran a faucet to bring the pressure down to 30 and turn the pump on (maybe 2 minutes). Once the pump kicked on I shut the faucet off and watched the gauge and switch... it hit 50 and shut off in probably 30 seconds.

What do you think that means?

Likely the pump is fine and we are drawing the well down too far when we use larger amounts of water? And after we use a lot of water and draw the well down, the pump is only pumping the water that is refilling the well through the ground/aquifer, and is probably cavitating some and sucking some air, but there is enough water flowing into the well to keep a steady flow and roughly 30 psi up top?

Yep. So, you need to test the GPM of the well and use less water than the well can produce.

 

[wpns]

Our well originally only made about 2GPM, and after a couple of decades of manual water management and irrigation zone juggling, we had it hydro-fracked, was over 13GPM, but needed an iron filter, should have done it originally. NOT inexpensive, but might be worth exploring.

 

[ESTIMATOR]

How old is your "pump tank"? How many gallons?

 

[Valveman]

Iron clogs up everything, especially well screens. Might need to shock the well if iron has built up.

 

[hamm107]

Sorry, missed seeing the notifications that there were messages.
We have a 5 gallon pressure tank that is probably 10-15 years old.
Interesting about fracking it. I would probably go in that direction if we owned this place, but we rent the house and fields. Why did you need to add an iron filter after that, does the fracking open up so many cracks that minerals are more likely to be in the water? Is a fracking also more likely to cause contamination issues down the road?

I wouldn't doubt that iron has clogged things up, have you guys seen screens on the pumps clogged up? It does seem like since I have good pressure and flowrate when I let the well rest and fill up that it's not the main problem though.

In the meantime, since I can't really use a 2-3gpm well which is probably around what we have, I started pulling from the river/stream near us for irrigation. 85' of head and 800' of line, but with a 6hp honda engine and a pressure pump I can get 40gpm at 35-40psi at the fields. That gasoline isn't cheap though. Maine used to be pretty reliable for an inch of rain per week, but not in the last 5 years. If you're growing you pretty much need a surface water source or a good well. A lot of people are just watching the radar looking for the chance evening thunderstorm to pass their way.

 

[wpns]

Interesting about fracking it. I would probably go in that direction if we owned this place, but we rent the house and fields. Why did you need to add an iron filter after that, does the fracking open up so many cracks that minerals are more likely to be in the water? Is a fracking also more likely to cause contamination issues down the road?

Maybe. In my case, fracking changed things enough that 'some iron in the water' turned into 'a lot of iron in the water', and I had to add an iron filter. I should have added the iron filter originally, and should have done the fracking originally, but hindsight's 20-20, you know?

If you don't currently have an iron problem, I'd be surprised if you developed one by fracking.

OTOT, since you don't own it, that's a negotiation with the owner...

 

[wpns]

We have a 5 gallon pressure tank that is probably 10-15 years old.

Do you have a CycleStop Valve, or when you say "5 gallon" do you mean 'drawdown' or total capacity? Seems kinda small...