Return Line Question

[corey.nolta]

I've been running my current set up for about 7 months now and I have not been able to figure something out regarding my return plumbing. On the return line from my sump I have two T offs. The first one (quick connect) goes to my reactor, but the second one (valve) I have no idea what it is for. What would / could this be used for? Did I set something up wrong? Or is it just an extra piece to the plumbing?
I initially thought it would work for water changes, but it definitely does not due to the baffles in the sump.
Thoughts / Suggestions????
(This was a build I purchased from a tear down sale, so the build is not my own)

Thanks!!

 

[Waters]

Could have been used for doing water changes...easy way to quickly remove water.

 

[BetURWrasse]

More reactors, uv, cleaning any number of things

 

[corey.nolta]

That was my initial thought when I originally put everything together, but because of the baffles in the sump it's only able to pull out less than a gallon of water. So I don't think that's what it's for.

 

[R_C]

Possibly to another reactor or if the pump was too strong to recirculate some water back to the sump. I have 3 reactors on mine carbon, biopellets and Rowaphos.