supply line and hot line from water heater both hot

Has anyone ever encountered this? Both the supply water line and the hot water line from the water heater are hot. Any idea why this might be?

Is there a circulating pump on the Hot water line … Roy


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Unfortunately, I did not get a picture of the water heater, but I do not remember seeing one.

As pressure in the tank rises, some water will move a little ways up the supply line to equalize. Also metal pipes will conduct heat pretty well. How far from the tank did you make your observation? What was the piping material? When you ran hot water in a fixture, did the supply pipe cool down?

Great points, Chuck. The lines were your typical copper lines. I didn’t check the pipe in conjunction with running the hot water to check for a drop in temp. Will definitely do that next time.

In all, I was wanting to know if this was a deficiency that I should call out. Both replies here have helped. Thanks fellas!

Copper is an outstanding thermal conductor

We just had a cold spell today, so I thought I would check my water heater surface temp and noticed that I get about the same temp (6 degrees difference) on both the supply and outlet lines. Going only 12" up I see a difference of 15 degrees and the gap only includes the farther I go up the lines. This could be both heat transfer through the water as heat rises and equalization. My lines are CPVC which is common for almost all new houses in my area and also is a poor conductor of heat which could point more towards equalization of the tank. All temps were taken without the hot water being used anywhere in the house and the water heater was not running at that moment.

Now to the strange question, should the supply line be insulated at least for 24" to 36", or is that just a waste of money?

Considering the cost of insulating material, I can’t say it would be a “waste” of money. If you pay more than a dollar for the insulation, you’ve probably over paid. However, you will not benefit from adding insulation to the cold water side of the piping.

Warmer fluids are less dense, so rise. Heat traps would be a good idea.

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