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Thread: Building a new home - 1 tank or 2?

  1. #1
    Water system engineer riverside67's Avatar
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    Default Building a new home - 1 tank or 2?

    I am in the process of designing a custom 3632 sq ft home that will have 2.5 baths.
    - powder bath = sink and toilet
    - Bath #2 = shower, rain shower head, toilet and sink
    - Master bath = 110 gal roman tub, two sinks, toilet and large shower with rain shower head, two wall heads and 1 set body sprays.

    I am currently specing 1-50 gal water heater that will serve the powder room, the kitchen, the laundry room and bar sink.

    The 2nd heater will be an 80 gallon that will only serve the master bath and bath #2.

    I am wondering if two tank heaters are really necessary? We have configured it this way since the house is 132 ft long and the master bdrm is at one end and the laundry, kitchen and powder at the other. We wanted to make sure we had a hot water source capable of filling the tub and/or not have to wait for 8 minutes before hot water got to our master bath shower.

    Does this configuration make sense?
    Would it be better to have 1 large tank heater to serve the entire home instead?
    Maybe something larger than 80 gallon?
    What about some kind of recirculating system to expedite getting hot water to the furthest parts of the home?

    I appreciate any help that can be offered!

  2. #2
    Illinois Licensed Plumber SewerRatz's Avatar
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    I have always found Bradford White's sizing guild to be helpful. http://rightspec.bradfordwhite.com/S...sidential.aspx The plumber installing the system can properly size and install a recirculation system.

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    Illinois Licensed Plumber SewerRatz's Avatar
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    Also AO Smith has a great piping diagram on how to install two tanks with a return line. http://www.hotwater.com/lit/wiring/315268-000.pdf

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    Retired Defense Industry Engineer jadnashua's Avatar
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    You can't get the full volume out of a tank, so, depending on the relative temperature of your cold in the winter and how hot you keep the tank, you may have trouble filling that big tub, especially in the winter unless you go bigger. Using a tankless (gasp) would likely require at least a couple in series to get the flow rate to keep the time to fill that tub to a reasonable interval...you wouldn't want it to cool off by the time it was full! You'll also want 3/4" lines and valves, otherwise it will take 20-30 minutes to fill the tub.

    I'm not sure either is a good choice...see what the others think. When you get to really large tanks, you end up in the commercial range, and some of those are designed to output huge amounts of hot water that would be fine for the whole house at whatever flow rate you'd normally use.

    If the heater is a ways from the furthest point, you'll want to have dedicated return lines so you can do recirculation, especially critical if the lines are 3/4". Make sure to insulate them well. If you lay them out properly, you may be able to keep the lines hot without a pump, although using a pump on a timer or occupancy switch might save a little, if you can wait. It definately will save water, and it is really nice having hot available without running the tap for awhile.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Extreme DIY Homeowner Scuba_Dave's Avatar
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    I have a single 50g electric feeding 2.5 baths
    But my ~3000 sq ft house is only maybe 50' from end to end for water delivery. So only 14' in one direction & 36' the other - plus 16' to the 2nd floor
    We have a hot tub outside, so we don't fill up the inside tub that often.
    Plus the inside jacuzzi tub has a heater built in

    Bradford sizing says 80g for me
    But the 50g works fine
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

  6. #6

    Default water heater

    Our house has three bathrooms with six bedrooms and the master bath has a 100 gallon whirlpool and a shower which is all being served by a 50 gallon high recovery heater for the past 19 years and it's been getting along ok that way with the consideration that no one can shower while the tub gets filled. when the heater gets replaced it will be with a 75 gallon tank. for your place i would suggest maybe one 100 gallon tank the two tanks sounds good too but it would cost more to operate two instead of one or maybe bradford white's high performance water heater.
    http://www.bradfordwhite.com/product...product_id=168

    Jonathan

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    Plumber jimbo's Avatar
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    I would take advantage of the spec. service available from Bradford White and Rheem.

    Even assuming that you will only put actual about 75 gallons into the tub, and 80 gallon tank in normal set up will only give you about 56 gallons of water hot enough for a bath. What you might want to do is get a high BTU unit, and also install a tempering valve, so you can set the heater up to a higher temp, around 160║. This will give you a larger volume of water hot enough for the bath.

    Given the length of the house, having heaters in two locations makes a lot of sense. If you don't do that, then a recirculating system makes sense.

    Although some of us have not drunk the "tankless coolaid" yet, you are an application where that could also make sense. But do a lot of homework. Many people tend to underestimate the size of tankless required, which is a fatal error. You also have to factor in annual maintenance cost into your equations. You MUST do annual ( perhaps twice a year in hard water!) service, or you will kill it.

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    Water system engineer riverside67's Avatar
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    Gusher:
    Thanks for the link! The BW 55 gal HP tank costs ~$1500. Would this be a better investment than two normall 50 gals in series?

    Where can I find a 100 gal tank?


    Jimbo:
    The water in our area is known to be quite hard. This may rule out tankless unless we install a softener (which we likely will be doing).

    I was hoping to have one 80 gal tank more centrally located for the home but the design doesn't allow that. I mean what's a few more minutes of water running besides the wasting water part right? Of course that means more $$$ down the drain...

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default water heaters

    The size and number of tanks is less important than where they are located. If you can position one tank near one center of use and the other one at the other end of the house, two tanks make sense. If they are both located at the same point then there is no advantage, other than storage capacity and recovery rates, for multiple tanks.

  10. #10

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    [QUOTE=riverside67;192390]Gusher:
    Thanks for the link! The BW 55 gal HP tank costs ~$1500. Would this be a better investment than two normall 50 gals in series?
    efficiency and recovery wise i would say so.
    Where can I find a 100 gal tank?


    I would assume your local supply house would have one if not then i dont know.

  11. #11
    Plunger/TurdPuncher kingsotall's Avatar
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    Quote Originally Posted by SewerRatz View Post
    Also AO Smith has a great piping diagram on how to install two tanks with a return line. http://www.hotwater.com/lit/wiring/315268-000.pdf
    Is that considered parallel or series┐ What is the difference as far as why one would be piped in any two ways┐

  12. #12
    Water system engineer riverside67's Avatar
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    That looks to me like it's parallel as both tanks are recieving cold inlet water at the same time. Series would be if one got the cold first and then the outlet of the first went into the inlet of the 2nd. Correct?

    Would running two tanks in series even make a difference in thier performance and/or is this even recommended by the manufactures?

  13. #13
    Water system engineer riverside67's Avatar
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    Quote Originally Posted by gusherb94 View Post
    for your place i would suggest maybe one 100 gallon tank the two tanks sounds good too but it would cost more to operate two instead of one or maybe bradford white's high performance water heater.
    http://www.bradfordwhite.com/product...product_id=168
    Jonathan
    We will be using LPG as our fuel where we are building. Can any "gas" tank heater be converted to LPG? I cannot find anything on the BW website that states specs about the GX-1-55S6BN being able to be ran on propane.

  14. #14
    Illinois Licensed Plumber SewerRatz's Avatar
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    Quote Originally Posted by kingsotall View Post
    Is that considered parallel or series┐ What is the difference as far as why one would be piped in any two ways┐
    That is a parallel set up which does require the piping from the tee to each heater to be exactly the same, meaning same amount of valves, same amount of fittings, and same exact length of pipe. Lets now say they both are 50 gallon units, now you have 100 gallons of hot water to draw off of.

    Now if you pipe them in series, where the first heater is cooking the water then the outlet of that heater feeds the second tank then the outlet of the second tank feeds the building. So here the school of thought is you are preheating the water to the second tank which will help make them recover faster.



    So basically you get more hot water in parallel, and faster recovery in series.

  15. #15
    Illinois Licensed Plumber SewerRatz's Avatar
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    Quote Originally Posted by riverside67 View Post
    We will be using LPG as our fuel where we are building. Can any "gas" tank heater be converted to LPG? I cannot find anything on the BW website that states specs about the GX-1-55S6BN being able to be ran on propane.
    When you order the unit from the plumbing supply just tell them its for LP gas Here is the link to the LP unit http://www.bradfordwhite.com/product...product_id=179

    I have installed a few of the GX-2-25 already, everyone of my customers loves the unit. They are able to fill their 80 Gallon soaker tub and there was water left over to shower or wash dishes. The unit also recovers really fast as well.

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