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piping 2 water heaters in series

mikedomikedo Posts: 74Member
is their any drawbacks to piping 2 fifty gallon water heaters in series. i have limited height and 1" feed for cold water

Comments

  • DZoroDZoro Posts: 492Member
    nothing wrong with it, if you have the need for 100 gallons of hot water on a constant basis. May want to consider a on demand system.
  • hot rod_7hot rod_7 Posts: 9,044Member
    No problem with series. We commonly did that with vacation homes, turn the 1'st one to vacation setting until the home is at full occupancy.

    The first tank will see most of the mineral and sediment build up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • IronmanIronman Posts: 4,589Member
    Are we talking gas or electric?

    If it’s gas, the second one will see a decrease in efficiency because of the hotter water temp entering it.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • JohnNYJohnNY Posts: 2,078Member
    I've never been a fan. Pipe them in parallel and they'll wear evenly and at half the demand put on the first tank in the series piping configuration.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    John is a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
  • hot rod_7hot rod_7 Posts: 9,044Member
    If you do want to pipe parallel 3 piping choices are, reverse return, "moose antler, or add a balance valve on both tanks to balance draw evenly. The balance valve option may help with your piping limitation issue.

    This drawing happens to be indirect with balance on the coil and potable water side.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Posts: 1,374Member
    Hello, My experience with parallel piping is often they get thrown out of balance just by corrosion or rust happening where nipples are screwed into the tanks or from dielectrics. If you can temperature balance the system periodically, parallel is fine. Otherwise, (as long as flow remains OK) series with bypass valves on each tank is my preferred way. ;)

    Yours, Larry

    ps, Water in my area can get pretty bad and that has everything to do with the sort of problems I see. If you have good, not very conductive water, there may be no problem down the road, going parallel.
  • hot rod_7hot rod_7 Posts: 9,044Member

    Hello, My experience with parallel piping is often they get thrown out of balance just by corrosion or rust happening where nipples are screwed into the tanks or from dielectrics. If you can temperature balance the system periodically, parallel is fine. Otherwise, (as long as flow remains OK) series with bypass valves on each tank is my preferred way. ;)

    Yours, Larry

    ps, Water in my area can get pretty bad and that has everything to do with the sort of problems I see. If you have good, not very conductive water, there may be no problem down the road, going parallel.

    Good point Larry, dielectric unions are notorious for corroding closed. With a 132 Quicksetter you could observe and re-balance from time to time :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • mikedomikedo Posts: 74Member
    thanks I'm just going to pipe them in series
  • JohnNYJohnNY Posts: 2,078Member
    hot rod said:

    With a 132 Quicksetter you could observe and re-balance from time to time :)

    Or you can pipe them in parallel and never think about it again.

    @mikedo You're doing yourself a disservice by going with series piping. But whatever.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    John is a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
  • GBartGBart Posts: 652Member
    edited July 12
    I was taught that parallel was the only way, there is reference material to back this up. In parallel the supply and outlet piping to each unit must be exactly the same and they must be equal units. In series the first unit typically does all the work, this can work if you are doing solar-another water heater, gas fired feeding electric, etc or if you have non matching size tanks. Piping in series usually causes the first tank to fail way before the other.

    Another option for series is a water heater piped to a aqua-booster to increase storage using the first heater to supply the aqua-booster.

    http://www.texasinspector.com/files/Water-Heater-Plumbing.pdf



  • hot rod_7hot rod_7 Posts: 9,044Member
    GBart said:

    I was taught that parallel was the only way, there is reference material to back this up. In parallel the supply and outlet piping to each unit must be exactly the same and they must be equal units. In series the first unit typically does all the work, this can work if you are doing solar-another water heater, gas fired feeding electric, etc or if you have non matching size tanks. Piping in series usually causes the first tank to fail way before the other.

    Another option for series is a water heater piped to a aqua-booster to increase storage using the first heater to supply the aqua-booster.

    http://www.texasinspector.com/files/Water-Heater-Plumbing.pdf



    If the first tanks fails earlier, seems the second tank lasts much longer, isn't it sixes at that point :) ?

    Any data to support the first tank failing way before the second?

    In our rental/resort applications series made more sense and I don't recall the failure rate you suggest?

    I'd highly encourage HW users to run tanks at 140 for bacteria reasons, so I doubt efficiency would be much different between first and second tank, we are talking 70% efficient appliances typically with standard tank heaters.

    I hate seeing bullhead tees, even on domestic water piping, as the parallel drawing shows. It doesn't take much flow resistance, as Larry mentioned to put them out of "balance"

    Series is nicer for recirc as you just circulate thru one tank.

    Seems like Rheem is fine with either piping method.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GBartGBart Posts: 652Member
    The first one does all the work, ergo it has more run time ergo it fails first, it's in several documents on line
  • jumperjumper Posts: 1,221Member
    GBart said:

    The first one does all the work, ergo it has more run time ergo it fails first, it's in several documents on line

    all depends. First one runs cooler? Series is often said to be no no but I don't see why.
  • hot rod_7hot rod_7 Posts: 9,044Member
    GBart mentioned parallel piping is the only way and you have reference material to back it up?

    The Rheem doc you attached seems to show series as an option? Although it shows a gas and electric In series, much different recovery rate tanks.

    Generally two tanks are used to cover large dump loads like filling a 100 gallon soaking tub for example, or multiple showers running at the same time, as in ski resort rental properties.

    So both tanks get pulled down to 100 f or lower. Under that type of use pattern I don’t see a much shorter life expectancy in the first tank. Consider tanks are engineered to a 6-7 year warranty these days.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • JohnNYJohnNY Posts: 2,078Member
    Why is there even a discussion on this? When you install multiple tanks/boilers/etc in parallel and fire them up from a cold start, you can watch and hear them fire up and shut down within seconds of each other. Forget about balancing valves. They're not needed. Isolation valves will do, and only if you want to include them. Setting the tanks at different temperatures is a guess at what's going to work best.
    Install them in parallel, same temperature, full flow (ie. half to each, naturally occurring), and you're done.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F, LLC"
    Or email John at [email protected]
    John is a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
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