Anybody know what this is? Looks like a bypass on cold water supply to hot water tank. One line has vacuum break going into drain stand pipe. Im not sure why it was done like this? Your suggestions are greatly appreciated. Thank you.
I’m not sure but I think it’s a pressure release valve. Not the TPR but one of another type.
Flow through trap primer
ahh… nice, thank you 
Looks like some sort of air bleed valve to me. It’s hard to tell from the picture though. Something similar to what is usually installed on hydronic heating systems. If that’s the case, it looks like it’s installed upside down.
It’s hard to say without actually being there and getting a true 360 degree view.
Right on, Barry. Just installed in a different manner.
what is it for?
Some plumbing codes require that floor drains (having p traps), that may not receive water for years at a stretch or even “never” , must have water supplied intermittently or, in this case, slowly through a constant drip through a small diam (1/4 or 3/8") tube to above the trap. This is to maintain the trap water seal.
Another method is to have the small supply pipe connected to a regularly used faucet. Each time the faucet is used, a small quantity of water is delivered to the trap.
I prefer the second method over the first as I have seen many of the drip type now not funtioning either due to corrsion, or possibly dirt, blocking the drip mechanism.
No matter how filtered or softened your water is eventually the minerals that escape that process will clog the drip. I agree Brian.