Water hammer loud thunk when submersible pump shuts off remove inards check valve at tank

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aviator79

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So this check valve has always been here at tank and after much reading seems consensus is that only check valve should be at pump and none above ground. So getting a loud thunk when pump shuts off assume could be due to this check valve so pulled and can see spring gone but plunger still there so thinking thunk due to check valve slamming shut after pump stops due to pressure in tank. I have been unable to find info on removing inards so figure make this post as I do it and test results.

Grabbed rusted nut with plyers and broke off easy, popped out plunger and figure just remove plastic guide as shown.

Cleaned up threads, rinsed out gunk and blew out with air compressor. Will clean threads on nipple adapter and tank, retape and may add very light coat thread seelent and reinstall.

If works then pump CV good, if tank drains guess will replace this CV for now and plan to pull pump. 282ft deep well.

Pump has Grundfos control box. Tank dated 2013 and where wired go thru wall looks like was redone so assuming pump replaced same time. Will see if can find paperwork and call town to find if permit pulled to confirm date and maybe figure out what pump is down there. House built in 1996.
 

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Reach4

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Good going on the check valve innards removal. Replacing the pressure tank without changing the pump would be pretty common.

What is CV in this context?

I would also check the air precharge on the tank. Air precharge is measured and set while the water pressure is zero.
 

aviator79

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Good going on the check valve innards removal. Replacing the pressure tank without changing the pump would be pretty common.

What is CV in this context?

I would also check the air precharge on the tank. Air precharge is measured and set while the water pressure is zero.
Thanks. I had been searching for info about removing innards on check valve and just couldn't find info. While I assumed would not be hard just like to find info before attemt. On rusted one like this clearly easy and assume non rusted can back nut off or just break but or cut plunger rod so ya it is easy.

Right my assumption that pump was replaced at same time is just assumption. However a pump lasting 26 years from when house built also seems unlikely? I've owned since 2014. Grundfos control box also looks new but still no idea age of pump.

CV in first post was in reference to pump internal check valve or one installed just above pump.

First thing I did yesterday was check precharge and was low. Showed 20psi after shutting well pump off and draining system. Brought up to 28psi as forgot to check pump on set pressure and was not sure if was 30 or 40. So after turning pump back on and seeing on set to 40psi I drained again and brought up to 38psi.

Still had thunk, though at first thought this had solved it as didnt hear it right away but it came back. Why was hesitant to say this solved problem but just watch another pump cycle and zero noise.

Was not sure this would work but today decided to remove innards of CV and so far seems to have resolved hammer/tank at pump shutoff and holds pressure.

However tank now gets to 70psi before pump shutoff. Used to be 60 so not sure if due to air in water side of tank...as certainly some would have got in there and have a hard time getting out with outlet at bottom. So think need to drain system again and drain tank and see if gauge settles back to show 60psi. Dont know how this would make a differende.
Switch reads just before gauge and gauge is new...so I guess can lower off set at switch if needed. Just dont fully understand what would cause change...my prv at tank not leaking like would expect if was actually seeing 70psi...idk. I'm new to this all.

I have some experince as I did replace WM boiler with WGO-3 (was oversized WGO-4) and redid all plumbing for that including adding 2nd pump for ID hot water tank as originally on a 5th zone valve, and other issues like expansion tank location wrong, added spirotherm, added valves all over to be able to isololate and fix as needed without draining, etc... did that on another forum but attached pic. Really need to see a before to understand but was a big job for me.

But in terms of well pump and such still learning. Expect will have to pull pump some day. Want to be ready.

Thanks.
 

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LLigetfa

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It is possible that water got on the air side of the tank which displaces some of the air volume so you would not get the normal range of travel on the diaphragm. Watch the gauge to see if it rises very quickly from 60 to 70 which could indicate the diaphragm is hitting an internal limiter dome. Also make sure that the air gauge is calibrated to read the same as the water gauge.sd

Lastly check that the nut on the small spring has not been changed from the factory setting. Normally the delta using only the big spring is around 20 PSI and the small spring if tightened would increase the delta.
 

Reach4

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Regarding the control box, check that for date codes maybe. If it may have been in service for 26 years, you might consider replacing the start capacitor before there is a symptom. Those are non-polarized electrolytics, and will go bad with time and starts.

Yet there is another possibility: the pump was replaced at some point with a 2-wire pump. And the box stayed, but the wiring just bypassed that to provide power straight through to the new pump. That would be more likely with a 3/4 HP pump. If the pump is 1.5 HP, a 2-wire pump is less likely. And with a well as deep as yours, a 3/4 HP pump is less likely.
 

aviator79

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It is possible that water got on the air side of the tank which displaces some of the air volume so you would not get the normal range of travel on the diaphragm. Watch the gauge to see if it rises very quickly from 60 to 70 which could indicate the diaphragm is hitting an internal limiter dome. Also make sure that the air gauge is calibrated to read the same as the water gauge.sd

Lastly check that the nut on the small spring has not been changed from the factory setting. Normally the delta using only the big spring is around 20 PSI and the small spring if tightened would increase the delta.
I can't say if water got into air side but when empty tank is light so I would say no.
Gauge increases linearly from 40 to 70.
Not sure how to calibrate as only single gauge. I can only say that yesterday pump would stop at 60psi. Now stops at 70. No real issue with that just need to figure out why.
Factory settigs are 30/50 per cover on switch but clearly main adjustment changed to 40/60. Cannot see noticeable marks but assume high limit not changed as said pump was turning off at 60psi yesterday as always had.

Could it be an air bubble in line to pressure switch? Idk (i dont know) if that could cause issue. Not familiar with how they work, if it has an auto air bleed valve or what, as assume when install line would be full of air unless attach to nipple on switch as water coming out of line. But any air in that line could throw off psig reading? where reads lower than actual? Again idk.

As is it works and PRVs not dripping so not too concerned and will figure out tomorrow.

Appreciate replies as this has been stressing me out as know the pressure spikes I was seeing due to hammer were high and wanted to resolve. Just wasn't sure I would solve. And hope at least others now can see how easy it is to pull guts from check valve if have same issue.
 

Reach4

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I don't think air would be a factor. If you want to reduce the cut-in and cut-out pressures about 10 psi each, rotate the nut on the big spring 3.5 turns CCW.
 

LLigetfa

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Before adjusting the nut on the big spring, loosen the nut on the small spring when the pressure is low. It can be loosened all the way until the spring is loose. Then check what pressure it kicks in and out which should be around 20 PSI difference.

As for calibrating the air pressure gauge with the water pressure gauge, just read the air pressure while the pump is running and compare it to the water pressure gauge. They should both read about the same unless the tank is tall in which case compensate 0.43 PSI per foot of height.
 

Valveman

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Before adjusting anything check the pressure gauge. Verify with a tire gauge on the tank, or drain the system and see if the gauge goes to zero as it should.
 

Bannerman

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or drain the system and see if the gauge goes to zero as it should.
Only the water pressure gauge should go down to zero.

While the water pressure is zero and the tank is completely drained of water, the tank's air pre-charge pressure should continue to remain at 2 psi lower than the pressure switch cut-in pressure.

yesterday pump would stop at 60psi. Now stops at 70.

Did you by chance adjust the smaller nut and the larger nut within the pressure switch? The smaller nut will adjust the differential pressure between cut-in and cut-out. That smaller nut is preset at the factory for 20 psi differential, which normally should not be adjusted.
 
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