Three Options for Replacing Old Water Heater

The Tank Three Options for Replacing Old Water Heater

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    A plumbing contractor gave me three options for replacing the 100 gallon commercial water heater installed in my four unit cooperative apt. I’m curious about the energy efficiency of these options.

    The first option is to install a 100-gallon commercial tank.

    The second option is to install two 50-gallon residential tanks piped in a way that will allow one to operate in the event that the other fails. How efficient is this two-tank system compared to a single 100-gallon commercial tank. Is it more or less efficieint to heat water in two tanks or one?

    The third option is an indirect water heater that will be connected to the new boiler installed in our building over the summer. This installation cost of this option is 50%-65% more than the first two, but it is pitched to me as more energy efficient than the first two options, and the indirect heater carries a lifetime warranty and can be considered a one-time purchase.

    Thanks for your time.

    Randy Schuyler

    I can’t speak to the third option, but doing two 50s in series — NOT in parallel — could give you pretty good hot water supply and cost a whole lot less than a commercial water heaters.

    Larry can probably comment on option No. 3. But we’re both still going to wonder about option No. 4 — Replace the dip tube and anode in the current heater. That’s going to be cheaper than any kind of replacement.

    The flow problems are not going to be solved by a new water heater. Those are obviously piping issues.

    Don’t let your plumber dictate the solution to you. YOU dictate it to HIM.

    Randy Schuyler


    Yes, I understand about option 4, and I will pursue that before replacing the heater.

    Given the age of my heater, there will come a time when it will have to be replaced, so I’m asking these questions for when that day comes. One of the other residents asked whether using two 50 gallon tanks was as energy efficient as one 100 gallon tank. That was the real impetus for my question. Now I know to ask whether the two tanks would be installed as a series or parallel.

    As for your comment about the price difference between two 50-gallon residential tanks and a single 100 gallon tank, the quote that I was given contained a $1050 differential. The quote did not give me a brand or model. I would ask for that information before going forward with any work.

    Larry Weingarten

    Hello: If the new boiler you’ll have is a condensing type, than you could heat your water far more efficiently than with standard tank type (or tankless) heaters. You also would have the more powerful burner of the boiler, so the indirect could hold fewer gallons and still meet demand. The boiler would need to be controlled to give priority to the domestic hot water, but for those who install boilers, this is common.

    I’ve seen a lot of discussion on this question and indirects win, both in terms of performance and life cycle cost 😉

    Now, if your boiler is non-condensing, the question is harder to answer.

    Yours, Larry


    How do I know if my boiler is a condensing boiler? I have a Burnham Independence 11. OK, from what I can understand, my boiler is not a condensing boiler.

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