I have a pipe valve labeled DH. I can't figure what it stands for. Does anyone know?
DH is connected to the bottom returns.
So, I was told it meant Deep Heat... anyone know what that means?
That is a good question! My guess is that it is on the discharge side of your plumbing since one says Spa Overflow and the other says RT1 (Return 1?).
Unless someone else chimes in, follow the instructions on our guide on How to Identify Pool Plumbing Lines and Valves and let us know what it does!