replaced everything, still hammer on cut out

[kelly]

Hello,
         After reading so many posts I decided to ask about my issue.  I have had water hammer and short cycles for the last couple years on pump shut off. I finally saved enough money to take care of this. Well first found out my tank was waterlogged and had 52 lbs in it, I thought weird, but let air out until new tank came in. I went with a Flexcon pro 32 gal. with a 9.5 draw, due that it fits under the stairwell so biggest I could go. I also upgraded from galvanized pipe, 1in, to a stainless steel tee and fittings, gauge, shutoff valve,etc. 40/60 d switch, I tied it all together with sharkbite fittings and copper pipe 1in, to the black poly line coming out of the basement floor thru 4 in corrugated. All set right? Turn on water and try, still have hammer, so much the black poly pipe moves about 2 to 3 in upward as it did before all of this, same issue. So I secured black poly pipe and verified tank pressure at 38 psi drained.  Then called well company, said probably check valve in pump, I said change pump, figuring it was due, being  14 years old.  So new Sta-rite Sk plus pump, 1/2 hp, 10 gpm, 2 wire 4in sub in well, replacing a red jacket pump. So all new, no checks at tank or pitless due to its only a 62 ' well static water level at about 20'.  Only the check in the pump, called well company and they are going to work with me and swap out the pump again, but they suggested putting an additional check right on top the pump. Is that ok or should the check be torn out of the pump first, don't know if 2 checks back to back is bad? I called Sta-rite tech line and they said their pump is fine,  I have some sort of plumbing issue.  Any way I had just ordered a csv1w to install at the tank, Just wondering if I'm just masking a problem, because I'm thinking the csv1w will fix my water hammer, and give me longer cycle time than 38 seconds from 40 to 60 psi?

[Cary Austin]

Filling a tank that hold 9 gallons in 38 seconds means your pumping level is so shallow that a 10 GPM pump is putting out about 15 GPM.  At 15 GPM through 1” pipe the velocity is pretty high.  Anytime you stop a pump while the velocity in the pipe is over about 5 feet per second, water hammer can happen, even with a perfectly good check valve.

But usually water hammer at pump shut off means the check valve is sticking in the full open position, and doesn’t close until the flow reverses.  A spring-loaded check valve is suppose to pull the check valve closed before the flow reverses.  But a flapper style check with no spring, like comes in many pumps these days, won’t close until the flow reverses, which can cause water hammer.

The CSV should solve this problem.  The CSV closes down to 1 GPM to finish filling the pressure tank.  At only 1 GPM, the check valve is only open the thickness of a piece of paper.  So when the tank is full and the pump shuts off, the check valve is almost closed already, and there is no reversal of flow and no water hammer.

Adding a second check valve, especially a sprig-loaded one may also solve the water hammer on pump stop.  But if the bottom check is sticking, as I suspect it is, the second check valve will then cause a water hammer on pump start.  So you would just be changing one problem for another.

[kelly]

The well company said they are going to swap out the new pump on Tuesday, I had talked to them today and if the hammer is still there,  they would pull the second new pump out, take out the internal check valve that's in the pump and put a spring loaded check valve,  stainless steel o-ring -Viton type, in on top of the pump. I believe made by Boshart ,(BII). PN 17cvss-100. I hope this cures it,  but I'm still going to install the csv1w to increase my cycle time to extend the life of the pump. thoughts?

[Cary Austin]

I think the spring-loaded check valve may solve your water hammer problem, but it won’t stop the tank from filling in 38 seconds.  With a tank that holds 9 gallons of water, you could get 9 minutes of run time if you set the CSV the same as the pump start pressure.  However, you only need about 2 minute or less of run time.

With the CSV reducing the amperage of the motor, the motor is “de-rated” so much that it doesn’t really need the 1 minute minimum that non-CSV systems need.  However, 2 minutes is still a good run time for the pump/motor.  So with a 40/60 pressure switch, you set the CSV at about 55 PSI, and it will only take about 2 minutes to top off the last ¼ of the tank at 1 GPM.

[kelly]

Update:
        The well company came out and this time I was there to observe.  They pulled out the new pump and installed another new pump.  All in and still had the hammer.  They pulled the second new pump out and reinstalled my original new pump, and I told them to rip out the pumps check valve and install the separate check valve on top of the pump.  So they did that and installed.  The water hammer was barely there, you really had to listen for it, otherwise you wouldn't hear it. They said there was nothing more they could do and the little hammer is just going to have to be there.  So I gathered a list of fittings to install the csv1w, and installed, I have the switch at 43/63 and the csv at 55, I used the washing machine filling as a setting and turn the csv screw clockwise, about 2 1/2 turns to regulate the water at 55 psi.  My run time from 43 to 63 psi is 2 min 11 sec. My system is totally quiet now, all I hear is the click of the pressure switch.  Your valve has totally fixed all my issues, hammer and to fast of a fill time.  I am so glad I came across your product, I am going tell all my friends, most of my area is all wells.      Thanks again KELLY    

[Cary Austin]

I am glad you got it fixed and thanks for the update.  There are a lot of people out there who argue with me about this very thing.  It is great to hear from someone who tried everything else first, then solved the problem with a CSV.  It is so obvious after you have seen it work, that using a CSV to reduce the volume and velocity to 1 GPM before the pump shuts off, completely eliminates water hammer by causing almost any check valve to close gently.

The same thing happens on larger systems like municipalities.  The engineers will tell you that the water tower or big pressure tank will catch the water hammer.  Transient pressure waves that cause water hammer travel at 3,000 to 8,000 feet per second. You can’t catch water hammer, it has to be PREVENTED. That would be like trying to catch a riffle bullet with your teeth.

The CSV will eliminate water hammer on municipal systems the same way it does for domestic systems.  Except on residential systems all you hear is the annoying “thump”.  In municipal systems that water hammer causes millions of dollars in damages to the distribution system and millions of gallons of precious water wasted.