I live in south FL and during the summer, evaporation is a big problem with my in-ground pool, 19000 gals. Every few days we have to refill and inch or 2. We do get some incredible rains during the summer which refill the level nicely and more. Therein lies the problem: the pool has an over-flow drain that's shown on this site as a Woodberg drain: . We can get 3" of rain at a time, but over night it's gone and we're back to evaporation... Does anyone know of some sort of cap or stopper or something that can temporarily close up this drain so we can save some of the water when it rains? Thanks for any suggestions.