[C320-list] Blockage in head sump pump hose

[Pat Ireland]

Mark

Antisiphon valves have a cap with a hole in the middle for a rubber vent
port that lets in air to break/stop any siphon flow.  The cap locks down
and holds the vent rubber in place.  Take care to review the correct
configuration of the rubber vent valve, because if installed backward,
water will leak out of the vent.  If the vent is blocked, it can not allow
air into the valve and water will siphon flow.  When installed properly,
pressure on the valve holds it closed.  When water pressure drops, air
bleeds into the valve and stops the backflow of siphoned water.

Good Luck - Pat