I recently purchased a home built in 1972. I don't believe the pool was original, but I would guess it's 20+ years old. My question is related to the plumbing. The pool deck is surrounded by concrete, so I can't easily dig down to see how the pool is plumbed. There are 2 suction lines coming into a 3-way valve which feeds the pump. I observe that one line sucks from the spa and one from the skimmer. The pool main drain seems to be clogged, since I swam down to the bottom and felt no suction with the 3-way valve turned either way. Is it likely that the pool main drain and the spa drain would be on the same line or, the skimmer and the pool drain on the same line? The pool is an in-ground 14' x 30' pool in southern California. It seems to me that in order to ever effectively heat the spa, I would need the spa suction line on it's own (there is currently no heater, nor do I know if there ever was one). But wouldn't the pool main drain need to be on it's own line in order to drain the pool? By the way, on the return from the filter, there are two line with a 3-way valve, one goes to the pool and one to the filter.
Besides all the plumbing questions, if anyone has some tips on unclogging the main drain, that would be great too!