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  1. #1
    Join Date
    Jan 2012
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    5

    Default Adding second water heater

    In anticipation of joining two families that will total 4 teenagers and two working professionals, we are renovating our 1 1/2 story cape and will be adding at least one full bath and a new laundry room as well as bedrooms. Currently we have a 2 year old 50 gallon natural gas water heater is not providing enough hot water for our needs on busy mornings when 6 people have to shower in a short period of time. So, I would like to add a second water heater. For various reasons I would prefer not to install at tankless heater in the new bathroom. There is no plan for a hot tub at this time. My question is: if I add a second 50 gallon heater, should they be connected in series, or in parallel? If I add a new, smaller heater, should they definitely be in series. If in parallel, should it be reverse return?

    Don't worry, a plumbing design consultant and plumber will be involved, but I want to be knowledgable about the situation.

  2. #2
    Join Date
    Feb 2010
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    South*East
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    1,168

    Default Re: Adding second water heater

    Why not just go with a larger heater? The cost will be close to the same and maintaining one heater is always better then two. Chances are that the gas line to your existing heater will be to small to handle two heaters. Also depending what type flue you have it may also be to small.

    John

  3. #3
    Join Date
    Jan 2012
    Posts
    5

    Default Re: Adding second water heater

    Good point! I guess since the present one is new I just didn't think about replacing it! From an academic side, anyone else have any answers to my questions?

  4. #4
    Join Date
    Jan 2012
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    5

    Default Re: Adding second water heater

    However, a new 75 or 100 gallon tank will be more expensive than a new 50 gallon one. Also, once the kids go off to college, we will not need the capacity except when they are all home. Having two tanks may allow one to be taken out use for much of the year, if it is plumbed correctly.

    Is there ever a situation where a tankless heater is put in series with a storage type? Would that be an option here?

  5. #5
    Join Date
    Dec 2007
    Location
    MN
    Posts
    455

    Default Re: Adding second water heater

    With 6 kids and 2 adults we get by pretty well with a 60 gallon tank. In the morning the rule is no 1/2 hr showers.

  6. #6
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: Adding second water heater

    Quote Originally Posted by Tola28 View Post
    However, a new 75 or 100 gallon tank will be more expensive than a new 50 gallon one. Also, once the kids go off to college, we will not need the capacity except when they are all home. Having two tanks may allow one to be taken out use for much of the year, if it is plumbed correctly.

    Is there ever a situation where a tankless heater is put in series with a storage type? Would that be an option here?
    Rather than using a 75 gallon tank (too small for you) or a 100 gallon tank (too expensive) think about this:

    Add a 40 or 50 gallon WH to service the addition only. You'll have to re-do the plumbing, bring in a new natural gas line and install a vent. You will need a permit.

  7. #7
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Default Re: Adding second water heater

    A good choice for you would be an on demand instant hot water heater. I have just looked into the rheem eco-sense and the rinnai. They make them up to 7 gals. a minute ,the average shower only uses under 2.5 gals. a minute now under new codes, so running 2 showers shouldn't be a problem, a 75-80 gal nat. gas storage water heater will be expensive to maintain that type of demand you describe, especially if you run 2 at 75k btu's a peice, that is a lot of gas usage, also the tankless sits idle when there is no hot water demand saving you lots of green, and being green at the same time.Your only other option is if you have a gas boiler you could pipe in a 75 gallon indirect water storage unit off your existing boier and combine that with your 50 gal. gas fired unit. And then you will have plenty of hot water. In my opinion the tankless on demand sounds perfect for you, when the kids are gone it just sits idle and your not heating more water than you need! Good Luck!
    Last edited by jled96; 01-06-2012 at 10:31 AM.

  8. #8
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,168

    Default Re: Adding second water heater

    Tank less is very expensive to purchase and install. First off you will need a larger flue then you need for your 40 gallon. Then you need a larger gas line. All this adds to the installation cost. You should also be aware of the newer clothes washers don't have a large enough flow rate to fire the tank less. This is also true of some new dishwashers. As far as maintenance,depending on your water condition the coil in the tank less needs to be back flushed with white vinegar or it will become plugged. In my opinion there not all there cracked up to be. As far as savings the average gas heater cost between $250.00 and $300.00 a year to run. Even if you saved 50% on your gas bill it would take 15 years to pay itself off. That's not counting the repairs to keep it running, if it lasts that long. But if your into the green thing and cost doesn't enter into it then go ahead and install one.

    John

  9. #9
    Join Date
    Aug 2008
    Posts
    69

    Default Re: Adding second water heater

    Regardless of which HW equipment you finally decide on, and select the qualified plumbing technicians to install it, you have to first determine how much hot water is going to be used during the PEAK HOUR OF HOT WATER USAGE; the PHOHWU can be calculated by following the chart at the site below, and as noted, will change when the teenagers are off to college, etc.

    You will then have to discuss these findings with the installers to make sure you're on the same page before the installation.


    http://www.ag.uiuc.edu/~disaster/replace/waterhtr.html
    Last edited by brewster; 01-06-2012 at 12:44 PM.

  10. #10
    Join Date
    Nov 2011
    Location
    boston,ma
    Posts
    114

    Talking Re: Adding second water heater

    Yes I agree John the tankless and the indirect storage are epensive to install, and some tankless need to be cleaned, some do not according to a fellow tradesman who is a licensed plumber. The things I found when discussing my best options were a power vent a,o, smith water heater was going to cost me $1400.00 installed in the same location as my existing 40 gallon water heater which is vented into the chimney(which I am no longer able to use because after removing the boiler the is insufficent draft for just the water heater alone) so instead of lining the old deteriated chimney I can put in a tankless heater which the price is $800 for plumber to purchase and $1,000 to install on a nearby wall, for a total cost of $1800.00. So this is a no brainer for my situation. So either way I need a direct vent unit that are both comparable in price, and the latter will pay for its gas savings in a few years, also the rinnai I am considering has a 5 years on parts and 15 year warranty on the heat exchanger and does not need to be flushed, the tank water heater has a 6 year warranty on tank only 1 year on parts. If you only need the water heater for 6 years the get the tank type if you want it to last for longer get the tankless! Good Luck!

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