Hot/Cold Mystery

[Donald Stauffer]

Fittings under a bathroom sink. My best guess it has to do with the hot/cold lines entering from a tankless water heater. Your view appreciated.

[Jerry Peck]

Farthest bathroom from the water heater?

May have been an autocirc (or similar) when there was a standard storage tank type water heater installed. Those are designed to keep hot water at or close to the point of use to save from having to run gallons of water to get hot water to the sink.

Another possibility is that is a tempering valve which keeps the hot water from getting too hot (it mixes cold water with the hot water so the hot water is not scalding hot).

[Donald Stauffer]

Thanks, Jerry.
Yeah, I'm guessing tempering mixing valve. I have one on a shower. Keeps hot water from scalding.
Close match pictures on Granger site.
Best to you.
Don

[Rick Cantrell]

All (2) tempering valves I've seen have Hot in Cold in and Mixed out piping.

[Jerry Peck]

All (2) tempering valves I've seen have Hot in Cold in and Mixed out piping.

Looks like that valve has three connections: left, right, bottom into wall ... looks like ... :)

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Auto circulation has nothing to do with a mixing valve.

I don't recall anyone saying they did? ???