What is this water fixture?

[mariner36bob]

Attachment 78771 this valve is inline cold feed to a water heater. Appears to restrict flow in direction of the arrow. What is it and it's purpose?

[Nicholson58]

hard to tell but - guess check valve. take the screws out and see what's inside - its a guy thing.

[Nicholson58]

could be a back-pressure relief. Free flow with a spring loaded valve designed to create back pressure.

[sailorchic34]

That is a check valve. It is generally not required for US water heaters, though it might might reduce hot water migration to the cold side. If you do install it on the water heater, be sure to add a expansion tank after it, so that the hot water when heated has somewhere to expand. The T&P relief will pop and dribble water into the bilge otherwise.

If you had a large yacht with a hot water return line and pump, then the check valve would be required. For small yachts its not really needed.

[Chasing Summer]

I agree ... besides being a guy thing ... it's probably a check valve. It prevents hot water migration when the engine or what ever you heat your water with in non-active.

[Uncle Bob]

Originally Posted by mariner36bob

Attachment 78771 this valve is inline cold feed to a water heater. Appears to restrict flow in direction of the arrow. What is it and it's purpose?

Looks like a non-return valve installed to prevent hot water expanding into the cold water system.

[mariner36bob]

Yeah I have a tendency to disassemble things that don't need it.

Sounds important.
Think I'll put it back.

thanks