Originally Posted by
Poconos
There are at least a couple types. One is the flap door that you mentioned and another is a cylindrical plastic device that fits inside a round skimmer basket. Hard to describe but the skimmer basket has slots vertically on the inside for tabs on the weir device to slide into. The slots and tabs keep it captive and allow it to float. There is an air pocket ring at the top to keep the top even with the water level. Does the same thing as the flap. When the pump stops the device floats and keeps crud in the skimmer basket from returning to the pool. When the pump is running the thing is sucked down a little to let water enter. If you need a pic I can do that too. The danger with either is the thing sticking and not letting water into the skimmer and the pump running dry. I have the basket kind and when the water level is high I've had it cock and stick high and water didn't flow. So...the fix, I don't use it unless the water level is below the middle of the skimmer opening.
Hope this helps.
Al