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High flow shower heads

If i have a high demand shower system, approximately 17 gpm, that will only be used once in a while, with an oil fired boiler and indirect HWH that has a 6 gpm continuous flow, what can i do besides upsizing the boiler or HWH? I don't want to add more equipment than needed for regular use. Perhaps a booster or something?


  • SWEI
    SWEI Member Posts: 7,356
    A storage tank

    is probably your best bet.  How long do you require 17 GPM of water, and at what delivery temp?  How often will you need this cycle to be able to repeat? 
  • Jack
    Jack Member Posts: 1,046
    It amazes me

    the number of people who buy these high flow fixtures with nary a thought to what it will take to feed them. Anyway, 3- 199kbtu condensing tankless will handle it all day long, or until the septic system blows up. To me, tankless is the only way to do these. you end up with multiple units but you have the capacity to use the fixture for as long as you are doing your thing in 17 fpm. When you step out of the shower, Junior can wash his hands and the system will fire as low as 10.5 kbtu. No standby losses which is the problem with big storage.

    I once had a guy proudly tell me that his shower head cost $5500. Total flow in the shower was 25 gpm. I proudly told him the equipment requirements to feed his play room. He was upset.
  • Zman
    Zman Member Posts: 7,434

    I seriously doubt the shower will actually use 17 GPM. It would take a very large domestic water line to deliver that much flow. Installing multiple tankless units would be very expensive and require a new gas meter in most cases.

    I would evaluate the actual GPM that the domestic piping can deliver and install a hot water heater with a tank big enough to handle the spike.

    I have installed a (theoretical) 6 gpm shower on an 80 gallon electric heater. I warned the owner of the potential problem and prewired for a booster. They have never had a problem. I am positive the owner would have had the booster installed if they had an issue as they paid 6k for the valve without blinking.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JIC
    JIC Member Posts: 4
    An engineer's job is

    to properly design a system that functions in the best interest of the customer at an optimized rate. At least a good engineer tries to do that. I don't want to waste water, I don't want to waste energy, but I do want to try to give them what they want.

    How often do people use these bells and whistles.. very infrequently. It sounds good at the inception. But no one ever "gets around" to really using these things.
  • SWEI
    SWEI Member Posts: 7,356

    hence my questions above.  With that information, a design will come forth and tradeoffs can be made.  For this kind of application, we always involve the customer in defining the requirements and then sign off on something which makes them accountable.
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,785
    One might want to...

    ... add a big shower heat exchanger  to make use of some of those BTUs going down the drain.  Might be cost effective!

    Yours,  Larry
  • Zman
    Zman Member Posts: 7,434

    If you determine the house pressure and the head loss of the piping going to the shower, you should be able to figure out how much water can be delivered to the shower. Just because the shower is rated at 17 gpm, that does not mean it will ever get there. If you have a typical 3/4" supply, you will never get that much water to the shower.

    I would start out with that number, then figure out how long the load will exist. From there you can design the system.

    If you start with 17 gpm you will likely be oversized.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Rich_49
    Rich_49 Member Posts: 2,703
    edited September 2013

    the temp in the water heater and use a tempering valve like the Taco 5000 . You should be able to produce damn close to your requirements then . considering that much of the water needed in this way is cold . With the right temp in the tank you should get away with .45 gallons mixing with .55 of cold to get you to 120* .  You could just pull it off without spending a lot of scratch .  By the way , there are only water heaters , not hot water heaters . Very common engineer , architect mistake .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
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