Loud Thumping/hammering sound

Irrigation systems, sprinklers & other watering topics
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Tgod288
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Re: Loud Thumping/hammering sound

Post by Tgod288 »

I rebuilt the sprinkler valve except for the body with no positive results. I then took apart the vacuum breaker and reassembled (waiting on parts to rebuild) and it seems to have made it a lot better. When zone one shuts off I can still feel/hear about 3 hammers in the pipe, but it is very faint. I would prefer no hammer like the other 4 valves, but not sure what else to do.

ionicatoms
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Re: Loud Thumping/hammering sound

Post by ionicatoms »

Tgod288 wrote:
Wed Jul 29, 2020 5:01 pm
I would prefer no hammer like the other 4 valves, but not sure what else to do.
This guy has three general suggestions for mitigating water hammer:
• Use a larger diameter pipe to reduce the velocity of the water.
• Close the valve more slowly.
• Supplement with an anti-surge device.

This guy has 4 suggestions that overlap the first guy: https://www.thebalancesmb.com/solve-wat ... ues-844851
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Re: Loud Thumping/hammering sound

Post by BadDogPSD »

Strange that it's just that one valve that causes the issue.

Topic Author
Tgod288
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Re: Loud Thumping/hammering sound

Post by Tgod288 »

Agreed. Think I will try a water pressure reducing valve at the backflow pipe.

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Tgod288
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Re: Loud Thumping/hammering sound

Post by Tgod288 »

except if the pressure is fine for the 4 other valves, then why wouldn't it be ok for the zone 1 valve? The pressure is about 75 psi.

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Re: Loud Thumping/hammering sound

Post by acampinoob »

I suspect Zone 1 may have higher flow than your other zones or is further away than your other zones from the PVB. This creates more water moving in the pipe at a greater velocity. It's the sudden "stop" of the column of water that creates the water hammer, not the static operating pressure of the water itself. You can see this in a roll of garden hose when you open the handle quickly and the hose roll jumps. Now imagine putting that in a straight line in a rigid pipe. All of the water hammer is directed in one direction (unlike the hose) and that's what you are hearing.

Topic Author
Tgod288
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Re: Loud Thumping/hammering sound

Post by Tgod288 »

Yes zone one is furthest and most sprinklers. I installed a water pressure reducing valve and it is still hammering. Don’t know what else to do at this point.

Topic Author
Tgod288
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Re: Loud Thumping/hammering sound

Post by Tgod288 »

If I stand at the valve box, I can faintly hear the hammer in the pipes underground when valve one closes. Is that worth worrying about?

acampinoob
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Re: Loud Thumping/hammering sound

Post by acampinoob »

As mentioned by others, you can install a mechanical water hammer arrestor. Don't do a length of pipe with air in it, because over time air diffuses into the water and becomes useless. Another option is to split zone 1 into two zones to reduce the speed of the water column doing the hammering. It's your call on whether to do it or not. If you've had your system for some time and haven't had any main breaks, I'm inclined to leave it alone.

ionicatoms
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Re: Loud Thumping/hammering sound

Post by ionicatoms »

Maybe swap to lower flow sprinklers and water for a longer duration.
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Re: Loud Thumping/hammering sound

Post by johnr »

@Tgod288 Perhaps you are dealing with a simple and common "water hammer" problem. That is, the water shuts off abruptly in your lawn system and sends a shock wave thru the plumbing. More details in linked article. Also note that the article mentions a 'simple' fix of just turning off the household water and draining your system, which clears the air chambers in your system, and you are ready to go. Hopefully one of us can help.

https://www.thespruce.com/fix-water-ham ... es-4126485

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