Water Hammer on Community Water System

[Tom101]

Hello Ron Kyger.  I talked to someone at your office and they said you could help me.  I have a 5 HP well pump that supplies water to about a dozen homes.  Every time the pump starts or stops I get a water hammer throughout the entire system.  How can I fix the problem?

[Ron Kyger]

The Cycle Stop Valve would eliminate your problem as long as everything is set up properly. What is your cut-in and cut-out pressure? How many gallons per minute are you pumping at full flow? What are you using for pressure tank(s)?

The way the CSV would solve your water hammer condition would be as follows:
1) Let's assume you are wanting a constant pressure of 60 psi. The valve would be adjusted to maintain 60 psi in your system.

2) Either adjust your current pressure switch to cut-in at 60 psi or install a 60/80 pressure switch. By doing this, the pump will start with a small flow which would eliminate hammer at cut-in.

3)  At cut-out, the check valve in your system is only open a couple thousandth of an inch. Your flow at this point is only approximately 5 gpm. Because the flow is minimal at cut-out, the system gently shuts down and hammer is totally eliminated.

What is likely happening now is that you are starting at 50-60 gpm which creates a "shock-wave" in you lines. The same thing is happening at cut-out; you're going from 50-60 gpm to 0. This too creates a "shock-wave". The pressures created at cut-in and cut-out are extreme and you cannot see the pressure spikes on your pressure gauge.

We have eliminated this problem for many people. If you get back to me with the specifics requested above, I can tell you what size valve you would need and the pressure settings for both the valve and the pressure switch. Also let me know about the pressure tank configuration you are using.

Thanks,
Ron

[Tom101]

Thanks Ron.  MY pump is a 40 GPM with a 5 HP motor.  It is 80' to water and the pressure switch is set at 60/80 on a 119 gallon bladder tank.

[Cary Austin]

Hi Ron, thought I might chime in.  Very good explanation of how a CSV stops water hammer.  I have learned something recently.  You do not have to have the CSV set at the same pressure as the pressure switch ON setting to eliminate water hammer.  With a 60/80 pressure switch you could set the CSV for 70 PSI and the pump will still start at 5 GPM with no water hammer.  It seems that even though the CSV is set at 70 and the pump starts at 60, the CSV will still be in the closed to 5 GPM position when the pump starts.  It will not stay in this position for long but, will still absorb the shock wave as the pump starts, then quickly opens to allow full flow from the pump until pressure reaches 70 PSI.  The loading chamber or bonnet of the CSV will be full of water holding the valve closed when the pump starts.  As soon as the pump starts, the flow from the pump will begin to lift the diaphragm to an open position.  The diaphragm will still only open as fast as the water in the diaphragm chamber can be pushed out through the pilot valve and control tubing.  In other words, with the valve set at 70 using a 60/80 pressure switch, the valve will quickly open when the pump starts but, will still make the pump start at 5 GPM which eliminates water on pump start up.  The CSV must still be set lower than the OFF setting of the pressure switch to eliminate water hammer during pump shut off and also to allow the CSV to function.

[Ron Kyger]

Thanks for the info on the cut-in pressure vs. CSV pressure setting Cary.

The tank size is perfect..you will have approximately 12 gallons of drawdown.

I need to know if you have any elevation changes from the wellhead to any of the homes on your system.

Thanks

[Tom101]

The houses start close to the well and the last one is up on the side of the mountain about 80' higher than the well.

[Ron Kyger]

Do you happen to know the manufacturer and model number of your pump?

The 80' of elevation gain could prove to be a problem. Does that home currently use a booster pump?