Question
I have a Hardi RD-600 Controller and 6 Hardi Solinoid Control Valves.  When irrigation is turned on "manual or auto" innitially the system "hammers" when valves open.  It appears this happens across the 6 zones.  Do the solinoid diaframs require replacement???   The system is about 10 years old.  Our water pressure (from street) is about 60-80 lbs.   Any help would be appreciated.
Thanks

Answer
George,
Sorry for the late reply.
The diaphragms don't normally need replacement unless the valve won't open or close. Water hammer is a tough one to resolve. It is a problem with the valves opening or closing too fast.
A few simple cures:
Look at the top of the valves, in the center, for a screw or handle. This is a flow control adjustment. (all valves don't have these)If you have this type of valve, try turning the screw in a few turns. This reduces the water flow a bit but may stop the hammering.
The other simple trick is to slightly close the supply valve to the system. By restricting the flow just a little, you may help the situation.
Good luck.

Matt