Inspecting a manufactured home, under two sinks I find a check valve allowing hot water to the cold water supply. Does not look to be original. Only at these two sinks, the water temperature was over 140 degrees F. Can anyone make sense of this?
Possibly a recirculation system. Did you see a small pump anywhere near the water heater?
Yes they had one at the water heater. It was a large house. So this is to prevent backflow to the pump?
I ran across something similar for hot water recirculation and took some time reading about since it seems cool but didn’t make sense at first. Here is a video of Taco Genie’s system with a great diagram starting at 0:13 in the video: Taco Genie
Some tankless water heaters give the option to use a recirculation system. It includes a pump and a check valve. A pump is located under the farthest, highest sink to draw hot water faster. Yours isn’t a pump under that sink though but the one near the water heater is probably doing the work. I won’t try to explain it all because the video can do better than me.
So as crazy as it looks, it allows hot recirculation so that you have instant hot water at the tap. when you turn on the cold water faucet, the pressure equalizes and runs cold. Hope that makes sense!
The ones I’m familiar with are temperature based. They shove lukewarm water back into the cold, until a preset threshold is reached, then they shut off.
I have yet to see one that’s just a pure check valve. That must work on pressure only, and won’t be regulated. Hope you like drinking warm water from the cold tap
In the one system I inspected that already had this installed, it wasn’t “instant hot”. It still took around 20-30 seconds to get hot but this was a large home as well as in an upstairs bathroom. I guess the benefit is hot water faster than without the recirculation and the cold water gets returned reducing wasted water.
You got it.
Faster hot water, not always wasting energy hot water.
The cold return is a cheap/existing home thing. It works better with a dedicated return line.