Experiencing water hammer when watering ends

Hi everyone.

Newbie here. I’m enjoying my Rachio unit but wanted to ask on water hammering. I have this enabled in the app and it definitely smoothes out when valves are turned on and water starts flowing. However, when watering ends, I hear a loud thud when the valves close. I’m afraid any potential pipe bursts. Any suggestions on how to fix this? Am I doing something incorrect in my set up?

Thanks in advance

From an app perspective, we just keep the previous valve open for about 10 seconds while the other valve is opening so there is a nice overlap. I can’t be that helpful regarding the thud at the end :wink:

Hopefully someone with more plumbing experience can help.


Water hammer is directly related to water velocity. This usually is the result of poor design. You can reduce the flow by changing nozzles, reducing qty of nozzles or increasing pipe size.
Overlapping valves works well until the last valve has to close. The water-hammer will reduce the life expectancy of you system. How much? Who knows.

1 Like

My neighborhood has 90PSI water pressure and this was causing me water hammer in part of my system. The fix for me was a pressure valve (this one) ahead of the valves.

1 Like

Wow, 90 psi? My gawd man. And I thought I was a stud at 76

We have 100-115 at the street. I put a PRV on the irrigation down to 70. House down to 50.

What if you make the smallest zone the one that runs last?

Yep… we did not realize it for years. We had leaky toilet valves and copper pipe joints leak a few times and finally a plumber noticed the contractor had not installed a pressure valve on the house and tested the pressure. Ever since we installed the valve on the house all the problem are gone.

I installed one myself on the irrigation pipe when we went to desert landscaping and drip last year. I have the house set at 60 and irrigation at 50PSI.

1 Like

Don’t forget to test the regulator yearly. They are a good part of my revenue. Regulators do work well and are required for high pressure. Water hammer however can be eliminated without a regulator by proper irrigation/plumbing design. Also, systems designed for a specific dynamic pressure may not perform correctly/efficiently at lower pressures. This usually is not a problem in residential applications but possible.

1 Like

I have a loud “thud” sound when my Rachio system turns on and again at the end of the watering cycling. Then again I hear the same “thud” sound when the dishwasher and clothes washer are done filling up with water. Our house is only three years old. I’m guessing crappy builder plumbing installation.

Here’s a great primer (among many great irrigation tutorials) on water hammer:


1 Like