I have a bit of a puzzle to work out...
To my simple mind, there should be 2 pipes between our pool shed and our pool. Filtered water, and unfiltered water. We are doing a landscaping/pool maintenance/rebuild project, and in our digging we have managed to unearth 3 lines to the shed. I don't know why we would have 3 lines.
A neighbour tells us that at one time a drainline to the deep end was leaking, and was abandoned. Would that be the third line? Or would that be the capped inlet in the skimmer (I thought the capped inlet made sense, but now I wonder...)?
In any case, if anyone knows where I can find a schematic showing how a pool is plumbed, I would really appreciate the info!
Edit to add: I found this online, which confirms my theory. Any other ideas of where that third line would be from? http://www.pool1.com/plumbing_basic.asp