Where do these pipes go?

[wdsheffer]

I've just about got my head wrapped around my pool's plumbing and equipment system, at least insofar as I understand what things do and what valves send water where. But I have two things I'm unsure of.

First, I've got two skimmers and a main drain in the pool and a drain in the spa. Here's a pic of where my suction plumbing emerges from underground at the pump. The pipe on the right is labelled "Spa Suction" so that's clear. The far left pipe must be the skimmers, since I know those are operating, and the diverter is open that way. Then I suppose the middle pipe is the pool main drain. How are the skimmers typically plumbed if they emerge as a single suction line at the pump? Is it a long run of pipe from the far skimmer to the pump pad with a lateral teed off to pick up the near skimmer? Or maybe two separate home runs teed together closer to the pump? Each skimmer has a single port in the bottom. Also, this main drain is clearly off, and I've seen numerous references to bottom drains being unnecessary and excluded from new builds. Will I ever have reason to operate the main drain short of using it to pump the pool dry?



Second, I have a booster pump for the Polaris pressure cleaner, and I have a pretty good idea that once the pressure side pipe goes underground it heads directly to the port in the side of the pool. However, the suction side pipe also disappears into the ground and don't know where it pulls from. Would it typically be teed off the pool return pipe? If so, I don't know why it goes underground to do that, when the return piping is aboveground about a foot away.



Any good guesses?

 

[BDY]

Re the skimmers - it all depends. My two skimmers run a short distance to a T in the middle of the two (which are on the same side) and then drop down a foot to run back underneath all the way to the pad.

With only one main skimmer pipe to pad it means there is a T “somewhere” but short of having the drawings or doing some fancy tracing work you won’t know. You will though have one skimmer that is the dominant suction due to less overall pipe distance to pad. you would have to have two skimmer pipes to the pad in order to have them be separately balanced.

Re main drain - I think the consensus seems to be to drain a pool with a sump pump not your pool pump. Many run the MD off or barely on for water circulation. It doesn’t hurt to have it on a little bit so long as your skimmers are having enough skimming action for your taste. The prior owner could have turned it off for that or for a leak too.