csv installation

[dooguy]

I have two csv installed on my water supply line going to my pressure tank.  They were installed when I had a new well drilled.  The well is 550' not sure where pump is placed probably around 500' level.  To prevent water hammer the csv's were installed.  After several years in service my supply line fittings have had some failures.  the pressure gauge between the two csv's will go to around 110 psi on well pump side until pump shuts down and then shows around 60 psi when pump is off.  pressure tank set to 40 -60 psi.  Is there a way to alleviate this high pressure that my pipe is seeing.  My pvc should be good to 200 psi (sch 40 pipe) but i believe this high pressure is causing my pvc fittings to fail.

[Cary Austin]

110 PSI is nothing.  Like you said your pipe is probably rated at 200 PSI, which means the burst pressure should be at least twice that much.  Most likely you have too many check valves.  A check valve on the pump is the only one needed.  If you have another check up top, especially before the pressure tank, the water hammer that happens between those check valves can cause 500 PSI spikes during pump start.  A steady 110 or even 200 PSI won't hurt the pipe.  But those little spikes between check valves will blow fittings or split the pipe.

[dooguy]

thanks for the reply.   Because of the depth of my well I have several check valves in the discharge line but none after leaving the well. I just have 2 csv's before the pressure tank.  Are you saying the  extra  check valves in the well could be causing the issue with fitting failure?

[Cary Austin]

Yes!  When the pump starts each section below a check valve crashes into the nest check valve up the line, which can cause severe water hammer and split pipes.  But why do you have two CSV's?

[dooguy]

I do not know why they installed 2 csv's.  I know there was a issue with water hammer when well was installed and they couldn't stop until they installed 2nd csv.  probably a case of pump guy not knowing what they were doing.  now that I am starting to have fitting failures and researching I am asking same thing.  I read the post or sticky about too many check valves.  All I know is it sounds like std practice to install multiple check valves on pump discharge.  i never questioned because i thought they were the experts on this.  You are saying 1 check valve is plenty on any depth well?

[Cary Austin]

Yes one check valve at the pump is the only one needed.  When was the water hammer happening, on pump start?

[dooguy]

i believe on shutoff

[Cary Austin]

Water hammer a second or so after pump shut off is from a bad check valve.  Either the check spring is broken or the guts are worn and the water must reverse direction before the check valve will close.  This will cause a loud bang a second or so after the pump shuts off.  Wear on a check valve like this is usually caused by cycling the pump on/off too much.