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Frequently Asked Questions / Re: How is Water Hammer Caused by Check Valves

« on: July 05, 2022, 12:02:16 PM »

The best way to eliminate water hammer on pump stop is to reduce the flow from the pump to a small amount before shutting off the pump.  As when using a CSV, the water flow will be reduced to 1 GPM before the pump is stopped.  At 1 GPM the check valve(s) are only open the width of a piece of paper, and there is no water hammer when the check valve(s) fully close after the pump shuts off.

With the check valve only open the width of a piece of paper is there concern of wire draw on the check valve as typically found in control valves where erosion or scoring of the valve’s seat and/or disc material is caused by the seat and disc being very close but not completely closed or tight at the shut off position. This is typical of a valve which is oversized for the demands of the application. This would render the check valve useless over time and if pump mounted in a submersible system could be a rather large repeat problem.