SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Glad we could help.
Have a good weekend.

I found your thread after googling my pipe thumping. I had the same exact problem which started after I finished the basement. I had a plummer state he would place a special valve outside my house with the sprinkler that would have to be removed every winter that SHOULD fix the problem. (Total price of $250)
After reading your fix, I remembered that the whole house valve was not completely opened when I first shut off the water to plumb the basement. When I finished plumbing, I completely opened the valve as I had always been taught.
After reading this, I turned down the main water supply and also solved the problem.
Thanks SOOO much!.

I believe I have fixed the problem.



And the solution could not have been simpler. I started thinking that this all started happening a year and a half ago, when our PRV stopped working, and I had a plumber replace it. Today I put a gauge on our hose bib, and saw that the house pressure was 80 psi (Only a little lower than the incoming 90-100). I think he adjusted it so that we'd have a lot of house pressure without it being so high as to cause water hammer. I got thinking about the theory that the fast water/instantaneous low pressure in the starting-up sprinkler line was drawing water from both sides of the tee, so I adjusted the PRV so that the house pressure is 60 psi.



I then tested the sprinklers. No more thumping. I can't believe it was such an easy fix.



Thanks for your help - trying to troubleshoot this one was not fun....

The ever-so-slight problem with that page is that it suggests placing a check valve in the house supply without first installing an expansion tank on the water heater. If you do install such a check valve, and there is no expansion tank, the water heater will do its job of heating water, and since heated water expands, the increased pressure can burst the plumbing.

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By the way, if you think about it, every home with an expansion tank in their plumbing, and no check valves, might be a likely candidate to create pipe banging when a sprinkler zone turns on. And yet, this isn't happening, and why? Because a properly designed sprinkler system doesn't have excess flows that create the pipe-banging problems.

Yeah you are probably right.
It sounds like a good idea.

Good Luck

I found another possible solution online - What do you all think of this idea?



http://www.rilawnsprinklers.com/blog/2009/07/noisy-pipes-when-irrigation-system-is.html



It seems to describe exactly what I'm experiencing. (The paragraph on "System is making a loud noise when the zones are starting, then the noise goes away until the next station/zone starts or only on specific zones.")

You said that the diaphrams did not fix the problem. What is the valve make and model that you changed the diaphragms? How many diaphragms did you change? Is there a Master Valve you can tell this by the controller? What is the model of the Rotor Heads you are using and what is the nozzle in there? Rotor heads will use more water or Gallons per minute the higher the water pressure. If you have High water pressure and you nozzles would use 2 gallons per minute with 50 PSI they will use 6 gallons per minute at 80 PSI. This is just an example, but you get the idea. If you are exceeding the recommended flow through your pipe size you will get the water hammer. 1 inch pipe should only flow 15 or so gallons off of the top of my head. 3/4 pipe should flow up to 10 gallons per minute off the top of my head. 1/2 inch pioe should flow 5 gallons per minute off the top of my head. Also you don't want the water in the pipe to flow faster than 5 feet per second. This is why the pressure and nozzle selection is so important in how many gallons per minute is flowing through your pipes. The cheapest way to fix it is to buy new rotor heads and use the nozzle that has a chart that can tell you how many gallons per minute are flowing with your high pressure and stay with in you pipe size flow chart recommended flow as I have outlined above. The next is to use flow control valves. You probably need new heads anyway. Unless this all started when you changed the heads or paid somebody to change the heads that did not know what they were doing.

Good Luck

Flow control valves are a good idea, since they can be throttled down, and that will slow a rush of water. Unfortunately, this isn't an easy problem to deal with, especially since it is mostly the result of poor system design.

Well, there's already a 3/4 inch copper supply line - I'm hesitant to go replacing that unless it's a surefire solution.



What do you think about replacing the valves with ones that have flow control? I've also seen pressure regulators that can be installed on the valves. In your opinion, is it more of an issue of high pressure, or high velocity?

Another possibility is to up-size the sprinkler supply, with the idea of reducing the effect of the large amount of water rushing through the supply line. Of course, in copper, this is an expensive solution. You see this phenomenon in systems fed from smaller-diameter plumbing far more often than from larger-diameter plumbing.

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Of course, the idea of installing a pressure reducer in the sprinkler supply, assuming you can stand to lose the pressure, has value in that a lower supply pressure can't produce the same initial flow that the higher pressure can.

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Beyond anyone's budget, are specialty valves that contain the means to prevent fluctuations. They don't open fully until the downstream pressure has risen to a set point.

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Reducing flows is as simple as changing nozzles on sprinkler heads. Experiment with a single zone first, that has all check-valve heads.