Swing Check Valves Slip - 1 1/2" - 3"
Check valves are essential when using a waterfall filter in conjunction with a pond skimmer.
The check valve will prevent water from the filter from back-flowing into the skimmer when the pump is switched off.
Check valves are also essential when an external pump is being used.
The Check Valve prevents the water from draining back into the pond or reservoir, keeping the external pump primed with water.