I reviewed this question and answer and there's probably similarities to this question, but wasn't sure what kind of setup I have. So I'm hoping I don't get flagged as duplicate.

We've got two gas heaters in the garage, but I don't really understand which one it is - parallel or series (from the first linked question). We have a 3 people in a single-story 4/3 house and I'd like to shut off one of them to conserve energy - if it actually would and if it is recommended. enter image description here Given this configuration, can/should I shut down one (which one) of the water heaters which probably isn't needed?

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    This is a parallel tank configuration, it appears -- albeit one totally lacking per-tank water shutoffs! Commented Nov 25, 2015 at 4:44

2 Answers 2


From your picture it appears they are paralleled.

To be seriesed the cold water would enter only one of them and the hot output from that one would be fed into the other's cold water input.

That is not what you have here. The cold water feeds both of them and the hot outputs are tied together. That makes them paralleled.

If you shut the gas off to one of them, the water to that one needs to be shut off or cold water will flow through the heater directly into the hot lines. You will need individual water shut offs installed on the one that is shut off. ThreePhaseEel is right, there should be individual isolation shut offs on each pipe of each heater.

Happy Turkey Week!


There is no way to tell from the photo, but in my house I have a similar setup in that I have two water heaters sitting side by side, but one water heater is designated for the master bath and guest half bath. The second water heater serves the rest of the house. So, if I turn off either water heater, part of the house is without. Ps. I agree about the water valves.

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