almost out of bullets on water hammer

[SGkent]

background - sprinkler system was put in about 1996. Water hammer started about 3 years ago. Sounds like a foghorn. Originally when it started it went off odd hours but only at night. You don't hear it in the house - only the back sprinkler valves.

* Replaced toilet valves and flappers
* Turned off washer, dryer, dishwasher etc to see if they played a apart
* Rebuilt PRV It is set to 60 PSI at rest and drops to about 50 psi when significant water is flowing like washer on warm. City pressure before the PRV is about 100 PSI. We now have water meters between the main valve and PRV but that was put in about 10 years ago so it predates foghorn.
* Installed a pressure gauge so I can see it easily anytime I am in the garage.
* Installed smaller water hammer arrester near kitchen sink because those pipes would hammer one time when faucet turned off before that arrester and expansion tank were installed. That hammer is gone.
* Installed expansion tank (ST-5) sized for 50 gallon water heater on cold supply side near water heater. It is properly pressurized for PRV to 55 PSI which is what system falls to when light water is used like a single faucet. Highest volume sprinkler line or clothes washer on warm drops water pressure to 50 psi. The pressure on the gauge never climbs above 60 PSI that I can catch it and I have looked at that gauge a thousand times now. The PRV appears consistent.
* As I recall PRV is installed before the water take off because sprinkler valves can't handle 100 PSI, and drip can't drop 100 PSI on drip regulators.
*Installed all new 12 sprinkler valves. The foghorn has not gone off on its own since then but it does so when a sprinker is turning on or off. Usually #2.
* Considered that a Ham Operator down the street is overloading the Rainbird Controller and causing it to chatter when his antenna is pointed this way. Odd hour only at night foghorns might be his signal causing the contoller to pulse 24V AC to a valve randomly. Starting to reach now.
*Considering making a water hammer arrester per a plumber's suggestion at Lowes which is how he has stopped this on other systems. Online reading suggests a vertical pipe without a bladder is an old way that is no longer acceptable.
* I have rebuilt several faucets, made sure no hoses leak when this happens. I have never been able to catch it doing it and when it wakes me up at say 2am making a foghorn by the time I get out there it has stopped. That is why I replaced all the valves.

Anyone want to lend some bullets?

 

[Geofd]

you don't mention a backflow preventer on your lawn sprinkler system.....when ever im working on anything with a quick open/close valve I install a spring loaded check valve before that system usually within a foot of the back flow device on the house side ...which separates your drinking water from a source that could contaminate it or the public drinking water that backflow device must be a testable device which in city or town is required to test once a year

 

[Diehard]

.

 

[SGkent]

all 12 valves are anti-siphon and at least 8" above the highest sprinkler in their circuit. I thought anti-siphon valves acted as a backflow prevention device, and removed the need for a check valve. We are in area that does not flood.

 

[Geofd]

each states code are different
in mass there are 2 different testable devices.... one were the device is a min of 12" above the highest head the other is used when the device is below that
the spring loaded check valve before the back flow device stabilizes pressure flucuations

 

[Geofd]

each states code are different
in mass there are 2 different testable devices.... one were the device is a min of 12" above the highest head the other is used when the device is below that
the spring loaded check valve before the back flow device stabilizes pressure flucuations

that spring check is a personal preference its not required

 

[SGkent]

each states code are different
in mass there are 2 different testable devices.... one were the device is a min of 12" above the highest head the other is used when the device is below that
the spring loaded check valve before the back flow device stabilizes pressure flucuations

I haven't measured the height but they all could be 12" above the highest sprinkler. Whatever Rainbird specified in their specs is what I followed when designing the system. I think I went with the anti-siphon because it was less prone to back flow.

 

[SGkent]

Well, we left the controller off for two nights and there appears to be no foghorn. Tonight will leave it on and see if it comes back. If so it will be either a defective controller or a Ham radio operator triggering chatter in the switching diodes that control the valves. Will be a strange one if it is. That said I have another question on water hammer that I discovered while testing the valves. When some of the valves turn on there is no chatter or unusual noise at the valve but there is a banging in the water heater. AO Smith 50 gallon. I get the same banging really loud if I open the pressure release and let go of it. Really loud. Metallic rap. Multiple bangs. I can put my hand on the water heater and feel it. I can also put my hand on the expansion tank next to it and barely feel it. Also hold my hands on the pipes. The noise is definitely inside the water heater. Are there baffles or things that can come loose inside them? This sound does not appear related to the foghorn on the sprinklers in the middle of the night.

Edit: I drained the water heater about half way to check the anode. The noise is the pressure relief valve. It thunks really loud unless released very slowly, This may be by design. What cause my eye is that it banged a little when the front sprinklers came on - even with an expansion tank next to it. Sounds like I need to add some kind of water hammer arrestee near the water heater or just live with it.

 

[SGkent]

update June 7, 2019. Two kinds of foghorn that sound the same. A short burst that is the sprinkler valves hammering when they shut off. That one a water hammer arrester will solve.

The other (unless the sprinkler horn is enough to shake the pad next to it also is the AC unit doing some kind of a pressure bleed about 10 minutes after it shuts off. We heard the long one go off while we were right by the back door - flew like the wind and I told Cathy who was ahead of me feel the AC unit as you pass by it on the way to the sprinkler heads next to it in case it is the AC. The whole thing was vibrating like a foghorn. Then as usual it petered out like someone letting air out of a balloon. Never made it to the sprinklers but unless they were vibrating the concrete pad the long foghorn is the AC. It wasn't running so it has to be some kind of residual pressure thing. Not a humm like a bad starting cap but a foghorn just like the sprinklers. I balanced a bolt on top of each sprinkler valve. Will see if they are there in the morning if the foghorn goes off again.

 

[Geofd]

if this is all related to your lawn sprinklers you need a spring loaded check valve within a foot of your backflow device on the house side....I also had an issue with water hammer in my boiler....so I installed a check valve on the cold water feed to my internal tankless and I split the domestic hot water feeds up by floor and I istalled hammer arrestors on each feed

 

[SGkent]

I was thinking about that but the articles are split on it. The valves are full anti-siphon at a correct height so they meet California code. I have the water hammer arresters - got them yesterday. Didn't have time to day to dig up the line to the sprinklers and design something so the arresters are in air space and not contacting soil. What brand and style check valve did you use?

 

[Geofd]

I was thinking about that but the articles are split on it. The valves are full anti-siphon at a correct height so they meet California code. I have the water hammer arresters - got them yesterday. Didn't have time to day to dig up the line to the sprinklers and design something so the arresters are in air space and not contacting soil. What brand and style check valve did you use?

don't remember the brand but I used an ips(iron pipe size) that way I could use a male adapter on one side and male by copper union on the other so it could be changed out easily so if those valves meet code install the check valve before them I would hold off on the hammer arrestors and try the check valve first....the checks valves could have been febco or appollo not sure.....

 

[SGkent]

thank you

 

[Diehard]

@Geofd
I do remember the recommendations for the use of a check upstream of backflow preventers to prevent chattering and such.
What I don't remember is whether it matters if they are swing check valves or spring loaded check valves or either.
I know in the bigger sizes that I typically dealt with they were always swing checks.

Don't think Febco makes single check valves.???

 

[breplum]

I have solved a very similar noise issue by replacing the PRV.
Either a higher flow capacity type like Watts U5B or using another brand and oversizing.
What PRV is in there now.
I have had so many defective PRVs out of the box, that we only use double union models now. Saves your butt, when you get defects.
Personal defective-out-of-the-box experience: 4 in 44 years. various brands.

 

[SGkent]

It is a Wilkins. Soldered and screwed on. Not easy to replace but I have rebuild kits, I bought about 40 years worth before they went rare. Usually about every 5 to 7 years I rebuild it. It holds pressure very steady and the pressure drop with flow is well within the allowable amount. A similar model now is like $400. It is set to 50 PSI right now. That is a bit low but we live with it and California these days has Jerry Brown pricing on water.

 

[SGkent]

coming back to update this thread. Last month I noticed that although the PRV was working, it had about a 1 1/2 to 2 second delay in adjusting pressure when the washing machine came on so I rebuilt it again with a new kit. The pressure would fall way down then pop back up and hold steady. It turns out that the internal valve body was very hard to move by hand. The new one was like silk when it moved. Either corrosion or just bad clearances when the old one was made. With the new valve the pressure regulates immediately, the pressure needle barely fluctuates, and this morning when we turned the sprinklers on - no more hammer. What was happening is that the pressure would fall when the sprinklers came on then as soon as there was enough differential the valve body would move and the pressure instantly recover. That delayed pressure swing was hammering the whole house as the expansion tank unloaded and loaded.