Very new to owning a pool/spa and this site has been indispensable. I've gotten the pool (mostly) in order and now am familiarizing myself with all of the functions of the spa. Had a new 333k BTU Sta-rite propane heater installed which has worked wonderfully.
What I'm still trying to figure out is the function of this piece of the spa:
Referring obviously to the bit next to the return.