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Irrigation / Re: Downhill water hammer

« on: December 04, 2019, 01:42:45 PM »

Anytime the pump shuts off while pumping maximum flow rate, as with a relay and timer, the check valve slams shut from the wide open position.  When you valve down the flow rate to like 1 GPM, as is the case when using a CSV, the check valve is barely open and therefore there is no slamming shut causing water hammer.

However, in your case you may simply get rid of the water hammer problem by switching the "flapper" check for a spring loaded check valve.  The spring pulls the check closed as soon as the flow stops and doesn't have to wait for the water to reverse the way a flapper check does.

I have a 3HP Sta-rite DHJ too at the edge of a pond. My check valve is almost closed at 2 GPM. Is it defective then?