Check valve necessary on cold water supply?

[briandm]

I'm trying to find out if I need a check valve on my cold water supply line to my water heater.
I have a tankless water heater, 2 gal expansion tank, and a separate recirculating pump. I had to replace part of my stack that cracked and noticed a check valve on the cold water supply that feeds into that loop. It's faulty and putting a new one in would not be simple because of location/complexity of the space. So before I tore apart wall and equipment to redo enough of it to give me space, I thought I'd check if it's even necessary. I've looked and I can't find anything in Washington/King County code in my searches, but I'm not sure if that's because there is no requirement or because I'm searching for the wrong terminology.

Does anyone happen to know if this is required in my location (Washington/King County) or have advice on what to search for to get an answer?

Thanks!
-Brian

 

[SHEPLMBR]

Why o you have an expansion tank if you have a tankless?

 

[sarg]

If on a municipal water system a check valve is "usually" required to protect from contamination. If on a well the only check valve would be on the pump to make the system function.
With the independent expansion tank that indicates municipal water..... unless your "expansion tank" is really a pressure tank.

 

[Twowaxhack]

Typically if the water provider requires a check valve it’s at the water meter.

You may or may not need the check valve to make your plumbing system operate.

Some codes require an expansion tank, period. I don’t know if yours does. If your tankless heater has a buffer tank and you circulate your hot water, that’s why you have an expansion tank and it might be why you have that check valve on the cold line.

 

[Geofd]

We use check valves on our domestic hot water systems if there is a circulator pump, the reason is if the building is dormant the circulator runs and heats up the cold into the heater, so you will get hot water out of both sides the check valve prevents that

 

[briandm]

Thanks all. The practical issue of hot bleeding into cold makes sense as a possible reason and I'm ok seeing how it plays out without one.

I'm member of a large privately owned water association run off of several large wells that serves just over 1000 homes. I have double check valves leading to irrigation and home sprinkler system and the association concerns themselves with getting those checked every year. So I'm guessing I don't have a check valve by the meter.

I'm the second owner of our home and it's quite possible that it was a tanked system at some point and the expansion tank was a result of that. But no, I don't think the current tankless has it's own buffer tank.

If I were trying to read the local code, what terminology would I search for to see if there's a requirement?