Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Need Unlimited hot water....

ShesbutchShesbutch Member Posts: 6
So I guess ill just explain the situation, we bought a 50gallon gas hot water tank, was told by a cottage fibre mill manufacturer that it would be sufficient. Turns out its not. We need to fill 3 XL capacity household top load washing machines every 30-45 mins at 160F water. I really need to utilize the 50 gallon tank I already bought and wonder what the best addition to this tank would be for me. An additional bigger tank? An additional gas tankless on demand system coming off of it? Help!

We have soft well water high in bicarbonate if that makes a difference.


  • Larry WeingartenLarry Weingarten Member Posts: 1,773
    Hello, It seems that it would be very useful to have a clearer idea of how many gallons of hot water you really use. Do you use only hot water in the machines? Might it be possible to collect the drain water from a machine from one cycle and see how many gallons it is? Once we know the maximum hourly usage, it will be a fairly simple thing to help you design a system to meet that need.

    Yours, Larry
  • HVACNUTHVACNUT Member Posts: 3,263
    Is this a residential or commercial application?
    Can you tell us what brand and model of the water heater?
    160° is probably max temp on the water heater thermostat, so...
    Even with that load, an indirect water heater piped off a boiler, if there is one, probably wouldn't keep up with that kind of demand unless we're talking about a big honking boiler. I'm not sure if a tankless is even available for your needs. Maybe multiple tankless heaters.
    A commercial water heater (or 2) like ones used in restaurants and laundromats would have been a better route to take. You could say the onus is on the mill manufacturer but good luck with that.
    There might be other ways to do what you want so get back with the tank info and we'll see.
  • hot_rodhot_rod Member Posts: 13,182
    The manufacturer of the equipment should have information on how many gallons the machines use per cycle. You really need to get or determine that number to get the sizing correct. no sense in guessing again.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ShesbutchShesbutch Member Posts: 6
    Around 300 gallons(maximum) between 8am and 11am, and again at around 5pm-8pm. Alternatively, 210 gallons 3x daily instead of 2x. Currently, I can put a hot soak of 35-40gallons going, drain it and refill it, over and over every 40 mins for a hot enough temperature, but I need more than 1 machine working at a time with a temperature of between 140 and 160 at all times. I'm scouring wool and need to remove all the lanolin.
    My tank is a 50 gallon Rheem gas tank found at home depot. In hindsight, yeah commercial ones would have been better but I cant return this one and so Id really like to utilize it.
  • ShesbutchShesbutch Member Posts: 6
    So hourly usage, after spinning and draining, would be 100 gallons.
  • Jamie HallJamie Hall Member Posts: 12,691
    OK. So if we assume incoming water at 50 and outgoing at 160, that's a 110 degree rise. And about 800 pounds per hour. You either need to store that much or you need to find a hot water heater(s) which can do that -- somewhere between 110,000 BTUh input and 130,000 BTUh input at 80% efficiency.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ZmanZman Member Posts: 5,734
    Here is the reality of this. Your 50 gallon tank is effectively only storing maybe 35 gallons at 160 degrees. With a long demand period like yours, the 35 gallons is getting used up quickly leaving you with only the production capacity of the heater.

    In theory your 100 gallons per hour would only require 1.67 gpm. I would be willing to bet that the machines fill fairly fast and that you would need at least 4 gpm during the fill cycle (I would recommend asking the manufacture for a real number)

    Your home depot heater is likely 40,000 btu/hr input and 75% efficient. 40,000*.75 = 30,000 output. The water coming out of the ground is probably 45 degrees or so, you are trying to make it 160 degrees giving you a delta T of 160-45=115 degrees. If you use this formula (Btu/hr=gpm x delta T x 500) and flip it around, 30,000/115/500= 0.52 gpm of production, you have found your issue.

    A 199,000 btu , 90% efficient on demand unit would produce an additional ((199,000 x .9) / 115/500)= 3.11 gpm. Keep in mind that gas line sizing and venting will be different for a the bigger unit.

    You either need to slow your fill rate or increase your Btu's to make this work.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • HVACNUTHVACNUT Member Posts: 3,263
    edited May 2019
    I've seen people return cut pieces of sheetrock without a problem. They'll take the water heater back.
    Figure your needs and have a commercial water heater(s) installed. It'll probably be cheaper than experimenting.
    Again, if there is a boiler on site that will handle the needed domestic load as well as space heating, a large reverse indirect or two might work but you have to crunch the numbers.
  • ShesbutchShesbutch Member Posts: 6
    It states on all boxes of hot water heaters that you cant return them. At least here, anyways. I guess I could consider reselling it online but weve been using it for about 2 months so I doubt I'd get nearly as much back for it. I need to figure out something fast though because our budget is getting lower and lower as we set up more.
  • ShesbutchShesbutch Member Posts: 6
    So adding a tankless heater in tandem with the tank or 2 new tanks? Or 2 tankless? I dont think we have room or money for a big boiler, but its also providing our farm house with hot water and would have to change too much on top of everything else.
  • GrallertGrallert Member Posts: 442
    Without spending any more money you could try as mentioned above, to slow the fill rate of you washer giving the water heater more time to recover. Perhaps also spacing your washes out or decreasing the number of washes per day. Or both.
    I wonder if you were to install an on demand water heater before the tank, set to its lowest setting so the tank doesn't have to make up such a temp difference. I'm not a water heater expert so I'm just tossing ideas out there.
  • IronmanIronman Member Posts: 5,561
    Install a 199k btu tankless in series with your present tank water heater. The tankless heats it first, then puts it into your tank which will store it and maintain the heated water temp. You'll get about 4 gpm useable hot water.

    You need to make sure that you get a tankless model that will output 160* water. A lot of the residential models only allow 125* or less.

    Also: ignore the bs that some manufactures advertise about running a 199k btus tankless on a 1/2" gas line. Unless the developed length of line is 15' or less, you'll most certainly need a larger gas line.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Leon82Leon82 Member Posts: 655
    Someone who services restaurants may carry a line of commercial tankless heaters which will hit 160.

    The owner of the plumbing supply place also told me that Bosch had a control board that would go to 160 instead of 140 on their commercial units but didn't adverize them. They also have a 225k btu unit.
  • rick in Alaskarick in Alaska Member Posts: 1,073
    I know Rinnai and Navien can both go to 160 with the right settings. I know the Rinnai needs to have a different control to make it go that high. I have one of each one of the two heaters in a restaurant setting that are set up so that they heat and store water in a water heater tank. So far they have been able to keep up with the kitchen loads ok
  • ShesbutchShesbutch Member Posts: 6
    Thank you everyone for all your suggestions!! Leaning towards the tankless. We're having a plumbing and heating guy come test our water to see if we can use one of them with our well water! :)
    Unfortunately I can't reduce the time it takes to do loads or the amount of loads I have to do, as I have a bottom line amount of wool I have to wash per day so that I dont fall behind in processing.
  • Intplm.Intplm. Member Posts: 1,127
    @Shesbutch Maybe look into a company called "Rinnai" properly sized to your needs. You might need a model 98? or greater. I have used this company (and others) with much success.
    Hope your plumber is helpful.
  • ZmanZman Member Posts: 5,734
    Shesbutch said:

    Thank you everyone for all your suggestions!! Leaning towards the tankless. We're having a plumbing and heating guy come test our water to see if we can use one of them with our well water! :)

    Unfortunately I can't reduce the time it takes to do loads or the amount of loads I have to do, as I have a bottom line amount of wool I have to wash per day so that I dont fall behind in processing.

    Hopefully you now understand what goes into figuring it out. Hopefully the plumber does as well. Best of luck :)
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Leon82Leon82 Member Posts: 655
    Do your machines fill all at once or fill and stop a bunch of times like the"high efficiency" ones?

    3 machines with the solenoids going on and off may cause enough pressure Spike to shut off the heater momentarily. A buffer tank of some sort will dilute the cold water sandwiches from this. You already have one with the heater you purchased.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!