How Swimming Pool Valves Work
Swimming pool valve operation can be one of the toughest aspects of pool maintenance to master.
First, you must understand that some valves are working under suction, and others under pressure, depending on the water flow.
Any valve coming from the front of the pool pump is working under suction. This is water being pulled from the swimming pool or spa. There should be a lid on the pump (usually clear or tinted) with a basket inside that catches debris and can be removed for cleaning.
This is the last point of suction. The valves are usually marked "off" on one side, and have a handle on the other side. Whichever way you point the handle is "ON", which means this is where the water is being pulled from.
From this point you can trace the water flow through the pump, filter, heater, and any other equipment until you find the RETURN valves.
These are the pressurized valves, and depending on which way you turn the handle will decide through which pipes the water returns to the pool. The Handle still decides the direction of water flow.