Hot water in shower but not in tub

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Hot water in shower but not in tub

Author: nattamby (NY)

Hello I have a combination tub shower. And the water that comes out the showerhead is hot, but the water that comes out the tub spout is not hot enough, and it’s actually pretty cold. I have a hot water heater that is tankless and is gas operated. I believe it’s one of those instantaneous water heaters. Please give me any advice you have on fixing the temperature in the tub

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Re: Hot water in shower but not in tub
Author: steve (CA) Is the tub the only fixture with this issue? It sounds like the water heater can't keep up with the higher flow requirement of the tub spout. Turn the shower on hot, then turn on other hot faucets and see if the shower water cools down.
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Re: Hot water in shower but not in tub

Author: bruceb3 (MI)

Good call, Steve. It must be a small tankless heater for this problem to happen with 1 tub being used. Check the maximum output of your heater. There should be a spec plate on the heater somewhere with its maximum output in gallons per minute (gpm). Then, check the maximum output of your tub faucet model. If your total demand for hot water exceeds the max output of the heater, NO fixture will get hot water. A spout allows a lot more flow than a shower head.
A solution would be to install a storage tank after the tankless heater. Then, install a recirc pump (if possible) on the storage tank, That should take care of any issues with running out of hot water.
If it's not possible to run a recirc line to the farthest fixture, they have systems that use a manifold under the farthest sink with a pump at the water heater. Let us know how it works out for you.

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