Irrigation causing water hammer, where to put PRV?

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GuitsBoy

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Hello all -

I have a late 60's early 70's colonial, and over the last 2 to 3 years, Ive developed severe water hammer from the irrigation system closing zone valves. I've done my best to secure the pipe hander and strapping everywhere I have access to, and have opened a few walls to try to find the source without any luck.

After seeing some suggestions online, I drained both the hot and cool side in the hopes any air chambers would be re-filled with air. I've not actually seen any air chambers, so I dont know if the house actually has any. However after draining and re-filling, I did see quite a lot of disgusting murky water come out the taps and shower heads. Not sure if this is evidence of the existence of air chambers (and stagnant water). At first, this seemed to have helped reduce the water hammer, but after a couple dozen tests runs, I've still had a few large bangs.

The city water service appears to be around 80 psi, which seems high but not crazy high. Ive already installed a small water hammer arrestor screwed into the outdoor tap on the irrigation feed line. This did not do much if anything at all.

I'd like to add a pressure regulator since my home does not have one. However, there isn't enough room between the water meter and the tee for the irrigation system. What's more, the sprinkler reach and coverage is already somewhat suspect, and I'm not sure I would want to further reduce it.

Directly above the irrigation tee is where the main ball valve is (aside from the old style valves on the meter). I'd likely have to install the PRV just above this. However I'm not sure installing the PRV on the potable water side would do anything at all to reduce water hammer.

Any thoughts on what I should do here? Should I try a larger hammer arrestor even though the small one didnt help? Should I install the PRV on the household water side even if the irrigation stays at the full 80 psi?

Thanks for any suggestions.
 

Tuttles Revenge

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Water hammer is caused by the mass of the water flowing through the pipes suddenly stopping by the quick acting solenoid valve. Water hammer arresters are supposed to be installed at the end of the line where the valve is located. It acts as a spring would.
 

Jeff H Young

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Regardless of water hammer or not . 80 psi is where PRV starts being required , So install your PRV at least to the home . and hope hammer goes away but either way you need a regulator
 

GuitsBoy

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Water hammer is caused by the mass of the water flowing through the pipes suddenly stopping by the quick acting solenoid valve. Water hammer arresters are supposed to be installed at the end of the line where the valve is located. It acts as a spring would.
Yes, I do understand that. The service entrance is 3/4 inch copper from the street, maybe 75 feet, and goes directly into the basement and meter. From there it Tees off one leg going to the irrigation, and the other leg feeding the rest of the house fixtures. When the sprinkler valves close, we experience water hammer / pressure spike in the rest of the house, even though its on a different leg. My best guess is that this is due to the mass of the water in the 75 feet of service entrance suddenly coming to a halt, and creating the pressure spike in the rest of the house.

Adding a small dishwasher sized water hammer arrestor on the irrigation leg has not helped at all. Its not behind the irrigation valves, but it's as close as I can reasonably get it. I have my doubts that a larger one would do anything either.

I dont think PRVs are fast acting enough to combat this if we put it only on the house leg. And if we put it before the tee, we'll lose coverage on the sprinkler system.

Not really sure what else to try.

Thanks for your thoughts.
 

Jeff H Young

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I have my doubts too that a larger arrestor will solve. but I don't doubt that at 80 psi you need a regulator. I think there is a good chance it will help but no guarantee.
 

GuitsBoy

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How about swapping the solenoids out for Slow Closing?
Are the solenoids themselves slow closing? Or the entire valves? The valves are dug into the ground, and replacing teh whole thing seems like a much bigger job than I'd want to take on right now. The valves are irritrol 205s valves which I replaced the diaphragms in a few years ago. If I understand correctly how they work, water from the inlet pressure side goes through the center diaphragm stem hole to fill the top side to close the valve. I could partially seal the center stem in the diaphragm with something to slow the flow of water to the top side of the diaphragm, but seems like it would eventually wear away. Its already a tight tolerance.

I have both a PRV and another larger water hammer arrestor arriving at the house today. I plan to put the PRV on the house side and the hammer arrestor on the irrigation side as close to the valves as possible. Hoping for the best.
 

Reach4

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Brilliant. When I looked them up, the solenoid controls a pilot valve, and that feeds water pressure to a diaphragm which controls the valve.
 

GuitsBoy

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Brilliant. When I looked them up, the solenoid controls a pilot valve, and that feeds water pressure to a diaphragm which controls the valve.
My understanding is that the supply water bleeds from the bottom of the diaphragm to the top of the diaphragm, and the larger surface area of the top chamber will push the diaphragm to the closed position. The solenoid opens to bleed off pressure on the top of the diaphragm (or opening the bleeder screw) and the reduced pressure on top can no longer overcome the higher pressure of the bottom, and the valve opens. The only place I can see for the water to move from the bottom supply side of the diaphragm to the top side, is directly through t he center hole that rides on the shaft/pin. closing the gap just a touch would potentially slow the migration of water, and in theory slow how quickly the valve closes.

But that all sounds like a big pain, so Ill try the PRV and big hammer arrestor first. They were fairly cheap anyway.
 

jadnashua

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An expansion tank has a significant volume and may work as a hammer arrestor for you. You'll need one when you install your PRV...see what happens after that install.
 

Reach4

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But that all sounds like a big pain, so Ill try the PRV and big hammer arrestor first. They were fairly cheap anyway.
Those sound expensive and PITAs compared to a pressure gauge.
Or maybe "The city water service appears to be around 80 psi" was your way of saying you measured your water pressure.
 
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Jeff H Young

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guitsboy, how about trying one thing at a time ? personaly I think the slow closing valves sound great but rebuilding them might do trick. but again the 80 psi is on high side and might just do it I dont usually get lucky just putting an arrestor but that could do it. These are all viable attempts and I wont argue with any of these ideas thjere is no book on stopping water hammers (well there might be) but there is a little guess work involved sometimes.
Let us know how you wind up Im just hoping you do one at a time for us to know how it worked out to know what " fixed it"
 

GuitsBoy

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An expansion tank has a significant volume and may work as a hammer arrestor for you. You'll need one when you install your PRV...see what happens after that install.
Thanks, I have briefly considered this since I thought I had an old expansion tank laying around, however I just cant seem to find it. The watts PRV that I purchased has a backwards flow valve, so no expansion tank is needed. Water can simply flow back into the city water system from the house, just as it does currently. The irrigation leg of course has a backflow preventer, but not the potable water side.
 

GuitsBoy

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Those sound expensive and PITAs compared to a pressure gauge.
Or maybe "The city water service appears to be around 80 psi" was your way of saying you measured your water pressure.
Yes. It fluctuates slightly over the course of the day, but measured at the hose bib, its normally in the 76 to 80 range. We have noticeable lower pressures in the early morning while everyone in the neighborhood is showering and sprinklers are going. I supposed this is because we are at the end of a dead end street. I have not measured the water pressure spike from the waterhammer, since my gauge doesn't have a tell-tale. I suppose a temporary solution might be to run the sprinklers during times of high demand, but that seems like a inconsiderate thing to do.
 

GuitsBoy

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guitsboy, how about trying one thing at a time ? personaly I think the slow closing valves sound great but rebuilding them might do trick. but again the 80 psi is on high side and might just do it I dont usually get lucky just putting an arrestor but that could do it. These are all viable attempts and I wont argue with any of these ideas thjere is no book on stopping water hammers (well there might be) but there is a little guess work involved sometimes.
Let us know how you wind up Im just hoping you do one at a time for us to know how it worked out to know what " fixed it"
OK, I can try the two separately easily enough... The 3/4" sioux chief hammer arrestor came in yesterday, and its a monster compared to the little washing machine sized arrestor. I'm suddenly feeling more optimistic about it. Ill report back with my results.
 

GuitsBoy

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Water hammer appears to be 95% fixed!

But I have bad news....

I can't positively state which one did it.

With the way irrigation branches off the main line after the meter, it made more sense to cut both lines at once, rather than try to wrestle and bend the copper, or stress the existing joints. I cut both at the same time, sweat the fittings in place, threaded in the hammer arrestor into the tee on the irrigation leg, and put the PRV in place between the union fittings on the potable water leg. The irrigation leg maintains the 80 psi pressure from the main, while the fixtures in the house see 50 psi now. The water pressure seems slightly reduced, but nothing alarming. Showers are still forceful enough at 50, and if need be, I can always bump it up a bit. Cycling through my irrigation zone valves, I no longer have a violent jolt in the pipes. You can feel the valve close, while holding the irrigation leg, but it no longer has the tremendous kick it used to. Upstairs in the bedrooms, the water hammer used to wake us from a dead sleep like a gunshot. Now I can't even make out the faintest sound as the valves close. In practical application, I'd say its completely fixed, though since I can still feel the valve close right where the irrigation leg splits off, Ill call it 95%. No matter what, we're in a much safer and much more comfortable position.

Thanks for posting your thoughts, everyone who chimed in. Thanks for helping my family sleep a little better at night.
 

Jeff H Young

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would have been easy to test it with a plug installed to determine if the hammer arestor caused improvement or the prv . glad it fixed though thought that would do it
 

GuitsBoy

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Yeah, youre probably right, but I dont have a plug at the moment, and its all nice and leak free, so I'm reluctant to try and do anything now.

However as a test, I ran a facet in the bathroom at low to medium flow to make sure the PRV was not completely sealed shut, then I cycled the sprinkler zone valve. I did not hear a clunk, and did not see much if any change in flow at the faucet. To me, this points towards the hammer arrestor doing it's job, and less towards the PRV being responsible for blocking the spike.

Had the faucet flow been greatly affected by the closing sprinkler valve, then I would assume that at times when nobody is running any water, the PRV was isolating the water pressure because it was effectively shut/closed.

Not a perfect test by any means, but at least a couple data points to consider.
 
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