Thanks for all the information on this site, it has helped me turn my green pond from a foreclosed house into a blue oasis. I am almost there! I have a question that has perplexed me for a while. I have three return lines into the pool, but the middle one (pictured below) was never pushing out water. My wife and I plugged the other two, and still nothing. This led me to put a hose into the pool end of the return line, and it popped off the cap of the pipe in the picture of the pump. The pipe is to the left of the return and inlet pipes. It seems like it is an isolated pipe that runs from the above the ground and straight into the pool. My question is why?????? Thanks!