I installed Rachio-3 and now whenever it turns on I have water hammering. I turned on the no water hammer setting but I am still having issues. Earlier it was only on one zone. However, now I get the water hammer when any zone starts. Someone experienced this and how to address?
The hammer prevention feature only works to prevent water hammer when running multiple zones, when switching from one zone to another. This excludes the first zone starting and the last zone stopping.
Was your previous controller not giving you water hammer at all?
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No. There was no water hammering before.
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Do you have a master valve?
Yes
Thank you.
@franz is it possible to do some testing on the sequence of turning master and zone valves on and off, and some timings? Could it help if master and zone do not open at the same time? i.e. open master first, then zone a second later? or the other way? could it be that some of these combinations reduce water hammer? Assuming the controller is unable to apply PWM to open the valves progressively?
Do you have a hammer suppressor? I had a system many years ago that had a very bad hammer, built a suppressor & it was still bad. I talked to a sprinkler supply store and they suggested changing out the cheap box store valves for better ones. I did and it reduced the problem tremendously. I have not used those valves since.
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The way that irrigation solenoids work, I don’t believe PWM would work. They are either “on” or “off”. The plunger isn’t moving more than a single mm or less, so not a lot of room for PWM.
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thank you! I was fearing this. Most movement would happen in a very short range of the percentage, so no benefit st all 
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Is there a way to set the PWM timing so that there is an overlap ( more than 10 seconds)between the two zones. Maybe adjusting that will allow two zones to be completely open before one of them closes. Right now the hammering is when every zone turns on. Everything was working fine until I replaced the rain bird controller with Rachio
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PWM (pulse width modulation) is the idea of slowly opening the valves, but since they are a solenoid valves, that can’t happen, even if Rachio had a way to ramp up voltage to the valve.
Water hammer is a result of your irrigation system “outflowing” the water source. If you have a bunch of GPM hungry sprinklers (or a leak) trying to run off a 1/2" spigot from the side of your house, the water is free flowing so fast, that when the valves close, it sends a shock back through the system.
There isn’t anything inherently different about Rachio vs. Rain Bird that would cause the issue. Both controllers send a small voltage to a solenoid to activate, which is an on/off command. If you are hearing water hammer at the start of the run, many times that can be an issue with a backflow device. There is a diaphragm and spring assembly in there that can wear out and when water starts to run, it will repeatedly open/close creating the effect of water hammer. You can get a similar effect if the solenoids on the irrigation valves themselves are failing.
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Agree that controller is not the issue. It may just be coincidence that problem started happening after the replacement. Checked for leaks and there is none. Only thing possible is back flow valve. Possibly it is bad and the line is emptied and during the starting of each zone water might be gushing causing hammering.
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I’m dealing with that issue right now on a small portion of my yard fed off a hose bibb. I’ve got parts coming to replace the guts or the backflow. I’m 99% sure thats my issue because of the fact that it happens at the start of a run.
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