Yes, It is white PVC. No, it is not from a heater. We do not have a polaris pool cleaner but the original pool owners did! It is probably a few feet below the pump and skimmers but it is not lower than the drain. My original thought is that it was a back up drain for leaks but the pool people (without looking at it) said there is no such thing. I have quit refilling the pool to see if it stops at a certain level. Right now, the level is 4 inched below the skimmer.

Thanks for any input!