Replacing the current gas heater with a smaller heater

Discussion in 'Water Heater Forum, Tanks' started by paulsiu, Jun 18, 2009.

  1. paulsiu

    paulsiu New Member

    Messages:
    32
    Location:
    Itasca, IL
    Hi,

    One of my relatives' water heater is leaking from the bottom. It appears that the bottom is corroded and probably needs to be replaced with a new one. They currently have a Richmond 7K50 50 gallon gas, 40,000 BTU. First hour is 74 gallon.

    They used to have several kids around the house, but they have all grown and left the house. The question is can they save some money and install a smaller unit. There is a GE Model GG40T06AVG01 at Home Depot that has a 40 gallon tank, 36,000 BTU, but the first hour is only 67 gallon. Do you think this is enough for 2 people and may be 3 (when someone visits). Will there be a problem with hooking up compatibility?

    The dad will apparently hook up the heater. He has apparently done the last two.

    Paul
    Last edited: Jun 18, 2009
  2. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Normal usage per person per day is 70 gal, some of which I guess is cold water.
  3. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,055
    Location:
    New England
    I was told some places determine the size of the WH based on the number of available bathrooms and fixtures; not how many are actually living there. So what's practical for you now might not meet code or the next occupants.
  5. paulsiu

    paulsiu New Member

    Messages:
    32
    Location:
    Itasca, IL
    I looked at various sites and gotten different ways of sizing a tank. Most of them follow a principal of calculating a maximum load from water usage.

    The relatives indicated their existing tank isn't very good. if they take 2 showers, the water upstairs takes a hit. Since the tank is 74 gallon first hour, how can that happen?

    Paul
  6. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    If the unit is old and not well maintained it's not as efficient as it once was.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,055
    Location:
    New England
    Another issue is the spec is based on the incoming water being a certain temp...if yours is colder, it won't produce as much hot water. One way to extend the capacity of the WH is to run it hotter, then mix the output with cold as required to keep it safe for people. This is done with a tempering valve at the output of the WH. This gives the effect of having a larger WH. It also can be safer since it is generally considered that 140-degree water is required to kill various nasty things that MIGHT be in the tank. Normally, this is only a problem when it sits, but 120-degree water (a common setting) is nearly ideal incubator temp for nasties.

    [​IMG]
    Last edited by a moderator: Aug 6, 2011
  8. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    74 gals = ~610#
    40F to 140F takes 18 kwh
    70F to 140F takes 13 kwh.
  9. Dana

    Dana In the trades

    Messages:
    2,865
    Location:
    01609
    If they have a hydronic (forced hot water) heating system with a reasonably new (less than 15 years old) boiler they should forget about a standalone HW tank and spring for an indirect-fired tank running off the boiler. It'll outlast the boiler, run at comparable or better efficiency as the standalone during the summer, and at signficantly higher efficiency during the heating season (improving the as-used AFUE efficiency of the boiler at the same time.)

    There is federal tax credit subisdy for this, and in many areas other incentives may apply as well.

    It's really the right way to go- more efficient, one burner to meet the two largest thermal loads, one appliance to maintain, etc, etc.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,689
    Location:
    Cave Creek, Arizona
    heater

    In most cases the difference in price between a 40 and 50 gallon heater is negligible. There are no compatibility issues with either heater.
Similar Threads: Replacing current
Forum Title Date
Water Heater Forum, Tanks replacing a gas heater, braided cold water inlet hose Aug 24, 2014
Water Heater Forum, Tanks Replacing two independent water heaters with one new hybrid water heater? May 8, 2014
Water Heater Forum, Tanks Replacing Drain Valve with Ball Valve Jan 9, 2014
Water Heater Forum, Tanks I'm replacing GE Gas Water Heaters that have failed. Why? Nov 7, 2013
Water Heater Forum, Tanks Replacing electric with NG.... need some advice.. Jul 16, 2013

Share This Page