Weird pool plumbing?

[hiandrew1]

Hi everyone, first post. Nice to meet you!

I've got a kidney shaped approximately 25k gal in ground pool, possibly built in the 60's. I've been fighting my aging pump and filter for a few years now and I'm finally replacing it. I've never been able to figure out exactly how my plumbing is set up...

I've got a drain in the deep end, a skimmer, and a suction port on the wall. As far as I can tell, most of the suction is coming from the skimmer, and that's where I've ran a suction vacuum in the past. The port on the wall's auction seems weak. Going into my pump is only one single pipe, I would expect more coming from the different suction ports, no?

Then on the return side I have an outlet pipe from the filter to a 3 way valve going to two return lines that I always thought had one to sewer and one to the pool, but I took the valve apart today while I have the pool drained and stuck a hose in each side. Both sides spit water out of the same return jets in the pool wall. Why would there be two pipes going to the same place and why would there be a 3 way valve on them?

There's also a wrist deep hole near my pool with a valve in it that I can't figure out the purpose of. Could this have something to do with the drain and skimmer lines?

What I'd like to know: what's up with two return lines going to the same jets? And why is my drain, skimmer, and wall suction all connected to one inlet pipe to my pump?

Just wondering if this makes sense to anyone. If it's an "I'd have to be there to look at it" kind of thing I completely understand. This probably sounds like a mess. Thanks in advance!

 

[kadavis]

Usually the main drain is connected to the skimmer. If there is two holes in the bottom the front one goes to the drain and the rear one is the main suction to pump. The valve in the ground, is it a 3 way? Probably controls the suction between the skimmer and the vac port in the wall. You can check this by turning it opposite of the position it's in, if the skimmer slows or stops check the vac port for suction. Of course a few pictures might help, not really sure about the return plumbing

 

[hiandrew1]

Duh, I guess pics would be good. Haha sorry about that. It's dark now though. I'll try to post some tomorrow.

The valve in the ground is similar to a water valve. Just on or off.

I took some more stuff apart and tried some more backflushing. Hose in the skimmer pipe trickles out of the wall suction, nothing else. It's entirely possible that it needs to be snaked. Hose in the inlet pipe makes water come out of the wall suction and a bit from the skimmer. Tried the valve off and on while doing this with no change. No response from drain that I could tell.

- - - Updated - - -

Also I put the three way valve back together and backflushed in both positions. One side sprays water from the wall jet, the other side backs up and overflows. Not sure where that other side goes to now...