What is this plumbing?

I am not sure what this is. The house has 3 water heaters and a boiler. The boiler appears to be connected to the radiant floor heat. The vertical copper pipe goes to a floor drain. Is this some kind of zone valve or relief valve? Could it be the backflow preventer? The boiler is in another room on the other side of the house.

Could be some sort of flush valve system Mike.


Thanks Mr. Larson. I am glad that I was thinking in the right direction.

I will make it easy from the PDF

Good catch Mike

Designed for installation on potable water lines to protect against both backsiphonage and backpressure of contaminated water into the potable water supply. Assembly shall provide protection where a potential health hazard exists.