Mystery ports on bottom of pool

[gkw4815]

I'm considering installing a SWG on my pool and did some digging around the pool equipment today in attempt to confirm that the blue-circled location in the attached picture is suitable for installing a SWG.

I did confirm that water flows through this loop whenever the pool pump is running in pool mode, so I think this location will be suitable.

The pool equipment features a red-circled three-way valve that has always had one of the outlets closed off since we bought the pool (ie the side flowing towards the chlorinator is open). I tried opening this closed-off side, and discovered that this causes water (as wells as a ton of leaves and crud) to shoot out of these two threaded ports in the bottom of the pool, roughly halfway between the shallow and deep ends.

Any idea what the purpose of these ports could be? It doesn't look like an in-floor cleaning system - those have a bunch of heads spread out through the pool, correct? If it helps - the pool was built in 1996 in the Houston area.

 

[DeltaP]

I think this might be a reverse flow conversion — where the pool is replumbed for reverse flow through the main drain(s) (effectively converting the main drain(s) from suction outlets to pressure returns), which is done by rerouting the main drain suction line to the pump output.

I wouldn't be all that shocked if the elevated section of pipe circled in blue in your first pic is part of the cross-connect installed between the original main drain suction line and it's new tie-in to the return/output side of your filter pump.

Edit: Dang it, I didn't notice that there was a smidgen of a drain cover visible in one of those pics. I think @mknauss probably has the right answer then. The spacing between those outlets is a little overly wide for a main drain reverse flow conversion anyways.

 

[mknauss]

Likely to send heated water to the bottom of the pool. Slightly assists in distributing the warmer water quicker.