My pool is 18 x 36 IG vinyl, and I only have one skimmer--no main drain. The skimmer is located just short of halfway of the length of the pool, and the two returns are located at either end of the pool, both on the same side as the skimmer. They do a very good job of keeping the pool clean, and I don't miss the main drain. I never close my pool, and I use my Poolbuster and Polaris solely to keep the pool floor clean.

The only time I can think that a main drain might be useful is if I had to drain water to close, or if I used a telescoping vacuum, but honestly, I don't miss not having it.

Janet