I couldn't believe they actually worked when I first hooked them up. I have two sump pumps, main and standby. First I replaced the check valve on the primary pump. When I started the pump I didn't hear the water flow through the check valve and there was absolutely no sound when the valve closed. The standard check valve that the plumber installed on my new build made a noticeable "pop" with the amount of water going into my sump every time it was closed, ie every 42 seconds. I knew I didn't want to live with that noise more than 80 times an hour, so I looked for quiet check valves. You are perfect! I sent my builder a photo of the box and valve installed and told him they made no noise and he said he would pass the information on to his plumber for use in his homes in the future. If you currently have a knocking check valve, replace it with one of these and the problem will be solved.
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