Indoor check valve BANGS at pump start

[Mooch91]

Hi all,

Submersible pump in a 150' well with an indoor check valve right at the inlet to the pressure tank. Historically, this check valve has BANGED (makes a popping sound) when the pump started, but it always did it intermittently. I'd go for months without hearing it, then it would do it consistently for a couple of months, then stop again.

Pump was replaced about 4 months ago. The BANG stopped. It has since returned over the last couple of weeks. Maybe it's correlated with the winter weather, or maybe it's a coincidence.

I've read a lot on here that if the check valve at the pump in the well doesn't seal, that a vacuum can be created on the indoor check valve, and when the pump is started, the indoor check valve releasing is the source of the noise.

Can the check valve on the new pump be bad already?

Other than the noise being a little disturbing, the situation does appear to be contributing to the pressure relief valve dripping ever so slightly. I have plastic piping in the house, so I'm not a fan of a continued hammer situation.

I did confirm that the pressure tank bladder is intact and the pressure on the air side is holding just fine.

Thanks in advance for any help!

 

[FredG]

Remove the check valve at the tank, and the hammer will most likely disappear, if you have no other check valves other than the one on the pump.

 

[Sponsor]

 

[Bannerman]

The only check valve to be utilized, should be the one at/in the submersible pump.

Remove the above ground check valve or alternately, prevent it from functioning by removing the internal components from within.

Without the above ground check valve present or functioning, whenever the pump is not operating, the pressure tank will maintain pressure within the drop pipe, all the way back to the pump's check valve, thereby eliminating the water hammer condition currently being experienced. Also eliminated will be the possibility for a vacuum situation before the above ground check valve which can cause contaminants to be drawn into the piping between the well and the pressure tank.

 

[Valveman]

As was said, remove or gut the check valve at the tank. Water hammer happens very fast like 5000 feet per second. The pressure relief valve doesn't see the 500+ PSI shock valve long enough to open up and dump water. But the prv is leaking because it is getting the same damage from water hammer as every other component in the water system.

Oh and BTW, that check valve is probably in the perfect spot to be replaced with a Cycle Stop Valve, which will stop cycling and the water hammer that is happening on pump shut off.

 

[Mooch91]

Thanks to everyone who responded. But isn’t there the possibility that the valve at the pump is currently leaking? I thought it was the vacuum caused by a leaking pump valve which holds the above ground valve closed, resulting in the bang when the pump is started?

I just don’t want to take out the valve and find I have a larger problem in the ground.

Thanks.

 

[Reach4]

But isn’t there the possibility that the valve at the pump is currently leaking? I thought it was the vacuum caused by a leaking pump valve which holds the above ground valve closed, resulting in the bang when the pump is started?

Possible.

I expect there is a check valve at/in the pump too. Removing/disabling the topside check valve will likely cause that bottom check valve to work properly. But be prepared to put that topside check valve back in if it is needed to work around a problem, until you get the pump pulled later for some other thing. More likely than not you will not have to put that top check valve back.

Another possibility is that the bottom check valve works perfectly, but there is the tiniest of leaks in the pipe. Water leaks out with time, and a vacuum (water vapor) forms down to about 30 ft above the water line. If the top check valve is removed, the pump simply runs every 15 hours to make up for the lost water. No vacuum. No bang.

What is your well casing-- 4 inch (4.5 OD) steel? or something else? Not directly relevant, but it is good to think ahead to when the pump does need replacing.

 

[Mooch91]

Possible.

I expect there is a check valve at/in the pump too. Removing/disabling the topside check valve will likely cause that bottom check valve to work properly. But be prepared to put that topside check valve back in if it is needed to work around a problem, until you get the pump pulled later for some other thing. More likely than not you will not have to put that top check valve back.

What is your well casing-- 4 inch (4.5 OD) steel? or something else?

I’m hoping it’s not bad after only 4 months but I guess anything is possible. Will be prepared to reinstall if needed. I’m hoping instead there is something wrong with the above ground one which has been in place for 18 years.

I thought diameter of well was 6” but not entirely sure off the top of my head.

 

[Reach4]

I thought diameter of well was 6” but not entirely sure off the top of my head.

Close enough... not 4 inch steel, so no special planning needed.

See the cross-section picture on https://www.ebay.com/itm/335419896492 for one type of check valve construction where removing the poppet is possible, but would still need access from both ends.

 

[Bannerman]

isn’t there the possibility that the valve at the pump is currently leaking?

Additional check valves such as the one located above ground, will too often prevent the pump's check valve from closing fully. Removal of the additional check valve(s), will usually result in restoring proper operation of the lower (pump) check valve since no vacuum condition can occur above the pump, and the additional pressure supplied by the pressure tank while the pump is shut off, will cause pressure to be constantly supplied on the lower check valve, thereby assisting the spring to close the lower check valve's gate/poppet.

The fact that an above ground check valve has been present for 18 years, is not an indicator that an additional check valve should be utilized.

Too many pump 'guys' don't appreciate the issues that an additional check valve creates, but they install then as that is what their Daddy and Grand Daddy had always done and taught them to do.

Of course, with additional repeat service work created, there will be little incentive to investigate why lower check valves are often not functioning correctly (seemingly), or why water hammer is occuring, resulting in drop pipe and supply line failure issues, usually requiring the replacement of those sections of pipe.

If for redundancy, you wish to utilize an additional check valve, an external one maybe threaded directly to the pump's outlet connection, thereby locating the 2nd CV within a few inches of the pump's internal check valve. In this manner, no vacuum condition can be created between them.

 

[Reach4]

Too many pump 'guys' don't appreciate the issues that an additional check valve creates, but they install then as that is what their Daddy and Grand Daddy had always done and taught them to do.

To be fair to those pump guys, there are voices that still contradict this. For example https://www.flomatic.com/news/submersible-check-valves-installation-when-where-why/ says "A common misconception is that just one submersible check valve is necessary for the entire system." I don't agree with that Flomatic statement, but it more than an old-timer passing information down. It may be Flowmatic's etc granddaddys. I would like to think they are not saying this just to sell more check valves.

So I go along with the thought that one in the pump and maybe one right above the pump would be best. But there are other voices out there. A check valve above the water line just does not make sense to me. Keep that piping pressurized when using a precharged pressure tank!