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What Size Water Heater Do I Need For An Entire 4-plex Apartment?

We have a 4-plex that is currently served with one 75 gal water heater. Each apartment has 3 bedrooms and 2 baths. I am not sure if the unit is “commercial” or “residential”. About 3-4 people reside in each apt. It is old and needs replacement. Thanks.

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  1. Comment by mr.answe
    August 16, 2009 @ 3:53 pm

    The major question you need to ask is: How has the old 75 gallon served you? If the tenants are complaining they are running out of hot water, then you need a bigger one, if not 75 is enough. One other option to explore is a tankless heater. These are quickly replacing the old style because they do not store hot water. Hot water is produced only as needed when called for, so you cannot run out. This also makes them much more energy efficient. The initial cost is more then the old style but will cost less due to reduced operating costs.

  2. Comment by William B
    August 16, 2009 @ 5:32 pm

    the average , is 25 gal per person, we have 2 -150 gal heaters for 50 people,
    i would suggest at least a 150 gal heater,

  3. Comment by ew a
    August 16, 2009 @ 5:49 pm

    gas 80 gal. elect. 120gal.

  4. Comment by hermitof
    August 16, 2009 @ 11:00 pm

    i would say at least 150 but 300 would be better as then you will know for sure that the hot water will not run out. and i suggest that you go with either a gas or oil fired hot water heater not electric. i live in a 4 unit building myself and it has an 80 gallon electric hot water heater and it takes to long to re coop after a large amount of usage. the only time we really have enough hot water is when the furnace is on in the winter time

  5. Comment by Flying Dragon
    August 17, 2009 @ 3:58 am

    Here is something you might want to consider: maybe instead of one huge heater, put in 4 (40 gal) heaters. Each apartment would have their own; if one breaks down, you only have one apt complaining. If apartment(s) are vacant, you can shut off idle capacity. The 40 gal units are manufactured in huge volume, so they are quite cheap compared to the huge ones. You could check the relative costs and energy use to see if it makes sense.

  6. Comment by Bart S
    August 17, 2009 @ 8:31 am

    I’m not sure if this will work in your application, but what about a “On Demand” water heater? (tankless)
    It heats water only when there is a demand for it. Thus eliminating all that standing hot water and wasting fuel to keep it hot.
    What does everybody thing of this idea?

  7. Comment by avonfrom
    August 17, 2009 @ 11:25 am

    Do you have a home warranty policy? If so, you could call out a plumber on it to get an estimate. A call-out will cost you about $35.
    Or call several plumbers that will come out and inspect for free. They can give you recommendations and you can make a good, sound decision from that point about which direction you should go to get the water heaters replaced (because, honestly, the one you have isn’t big enough for the complex).

  8. Comment by extex_co
    August 17, 2009 @ 2:58 pm

    You need a bigger one…or maybe two.

  9. Comment by 4 plex owner
    January 27, 2016 @ 8:22 pm

    I have a 4 plex and have a 100 gal unit. My 4 plex is on 1 bedroom apartments with a total of 9 people in it. The 100 gal supplies enough hot water. I have it over 15yrs without any complain on no hot water.

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