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We purchased a house recently that has two water heaters(configured in series). I just realized that the first one hasn't been running as the thermocouple was defective. For 6 months we had no problem using just the second one. If we don't need the extra water capacity is there any need/benefit to having the first water heater consuming gas? Would having the first water heater lessen he amount of "work" the second heater needs to do? Or, am I just wasting gas?

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up vote 6 down vote accepted

If you haven't noticed a lack of hot water, I would say there's no reason to have both water heaters running. Just make sure that the gas line to the one that's not working is turned off. While the second water heater is currently doing more work than it would typically do if they were working in tandem, it's not using nearly as much gas as you would if both water heaters were running.

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Note too that the only one you can shut off is the first. If you shut off the second one, you'll basically never got hot water because you'll have to run the tap to use the entire contents of the second (cold) tank, and due to mixing, at best, you'll get lukewarm water after 20-60 minutes. – gregmac Oct 22 '11 at 19:10

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