PK1A Installed 2 years ago - PVC Elbows started failing

[mwolf00]

In the past year, every single PVC elbow that runs from where the well pipe enters the house to the valve has failed.  They were all installed when the house was built in 2004.  They started by dripping and then spraying water when under pressure.  They did not break altogether but they got the floor pretty wet each time.

I never even realized that PVC elbows could fail as they seem so solid.  The pipe run is all 1" PVC and there were a total of 12 elbows in the run.  They didn't all fail at once and I'm not sure it is due to the valve but the timing seems a little odd.  I have replaced them all but I'm wondering if I should be using something other than PVC for that run - a neighbor has suggested PEX but I don't know anything about it.

[Cary Austin]

PVC is better than Pex. The glue welded part is the weakest link in PVC though.  1" PVC pipe is good to 450 PSI but the glue joint is only good to 270 PSI.  Even still, you should not be seeing anywhere close to 270 PSI back pressure.  Do you know what model pump you have and how deep it is to water?  Or, do you have a check valve at the tank or after the elbows somewhere that could be causing water hammer damage?

[mwolf00]

I'm really not sure about the well pump.  I seem to recall it is about 150' down and about another 200' from the house.  I am fairly certain that there is no water hammering happening.  I would hear/see it if I were next to everything when it started/stopped, right?  I could never actually tell where the leak was in the joint but the cement weld does make the most sense.  I observed one go from a small drip to a fine spray over the period of about a week so it was getting progressively worse over time.  It was never anywhere near a total failure.  Rather it was a nuisance that I needed to deal with when I could make the time.  Fortunately, the basement is not finished.

[Cary Austin]

If you have a check valve before the pressure tank, there will be water hammer.  You may not feel or hear it as the pressure tank absorbs most of the blow at that point.  But on pump start, the water hammer pressure before that check valve can be several times more than the pump can even produce.  Without knowing what pump you have, installing a pressure gauge before the CSV is the best way to find out how much pressure your pump can build.  Either you have a pump made for a 1000' well and it makes too much pressure, there is a check valve at the tank causing water hammer, or the glue was just bad from the beginning.  But that is not a normal problem.

[mwolf00]

On second thought, I definitely do not have a check valve.  It sounds like the issue is most likely poor gluing during initial construction.  All of the elbows have been replaced now.  I was just wondering if I need to do something to prevent future issues.  Overall very happy with the PK1A.  Thanks for your responses.

[Cary Austin]

There will be higher pressure on the pipe before the CSV than after.  How much pressure depends on the size of the pump and the depth to water.  That is one of the things we check when sizing a CSV to a pump system.  The CSV itself has a max pressure rating, and we want to make sure we are working with regular size pumps that can't build more pressure than the pipe or CSV can stand.

[mwolf00]

Eventually every single fitting failed.  I have had a plumber come in and fix some of them and install a pressure gauge before the PK1A.  This was after a fitting blew while I was out of town which flooded the basement.  The pressure in the well feed pipe runs about 50psi until the pump turns on.  At that point, it jumps to 170psi and stays there until the pump turns off.  Is there anything that I can do short of getting a new well pump to help regulate the back pressure when the well pump is running?

[Cary Austin]

Sorry for your problem, but I looked it up again.  1" sch 40 PVC with socket weld joints are good to 270 PSI.  You should have no problem with only 170 PSI.  Must have a batch of bad fittings.  Can you move the CSV closer to or install it at the well?  Only the pipe before the CSV sees the 170 PSI as after the CSV the pipe will only see the 40/60 from the pressure switch.

I do systems that require 150-170 PSI on the pressure switch side and have up to 256 PSI on the pump side.  Your 10/50 system with 170 PSI back pressure is normal and should not be giving you problems with fittings. 

PVC has a much lower pressure rating as the temperature increases.  Any chance you have heat tape or a heater on that pipe?