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Thread: Softener system for new home - ATTN GARY

  1. #31
    Water system engineer riverside67's Avatar
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    Quote Originally Posted by Bob999 View Post
    You seem to be saying that your design specification is 20 gpm of xx degree water for yy minutes. I suggest you check the temperature of the water in which you typically shower.
    Incoming water is ~ 57 degress F.
    Typical hot water shower temp is about 108 F.

  2. #32
    In the Trades Akpsdvan's Avatar
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    Why not do a few On Demand water heaters, first in last out..

    With close to 60F water and going up 50F to the 110F if you had 2 or 3 of the big ones, some how I don't think that you would run out of hot water, and be able to keep up with the flow demands that you might have.. and save room, and would not be heating water when you are not using it.

  3. #33
    Water system engineer riverside67's Avatar
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    You mean tankless?

  4. #34
    In the Trades Akpsdvan's Avatar
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    Yes tankless... there are many brands out there, find some that can handle flows from 1gpm to 15gpm and have two , first in last out so that you have the full flow, or a balanced header.

  5. #35
    DIY Senior Member Bob999's Avatar
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    A VERY large input BTU will be required with tankless heaters. If you assume 20 gpm of 108 F water and 57 F incoming that is a temperature rise of 51 F. So the hourly BTU input required is 20 gal times 8 lbs/gal times 51 degrees times 60 minutes equals 490,000 BTU/hour. If you assume the water heater is 80% efficient then the gross input per hour is 490k/0.8 = 612,000 BTU. Getting the required propane flow to support an input of that size will require a very large propane tank.

    Three of these units (http://www.cpotanklesswaterheaters.c...2700es-lp.html) would provide approximately 20 gpm for your conditions.
    Last edited by Bob999; 01-31-2010 at 06:29 AM. Reason: clarity, add information

  6. #36
    Water system engineer riverside67's Avatar
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    Quote Originally Posted by Bob999 View Post
    A VERY large input BTU will be required with tankless heaters. If you assume 20 gpm of 108 F water and 57 F incoming that is a temperature rise of 51 F. So the hourly BTU input required is 20 gal times 8 lbs/gal times 51 degrees times 60 minutes equals 490,000 BTU/hour. If you assume the water heater is 80% efficient then the gross input per hour is 490k/0.8 = 612,000 BTU. Getting the required propane flow to support an input of that size will require a very large propane tank.
    Bob,
    Considering the temperature rise requirements mentioned above, the typical 10 gpm and max 20 gpm hot water demands in the showers... would the two - 100 gal tank heaters be sufficient?
    Last edited by riverside67; 01-31-2010 at 06:53 AM.

  7. #37
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    seriously, have you figured the cost of a couple of 100 gallon tanks, oversized water treatment equipment, and all the installation, piping costs etc involved in taking a shower? You are going to have close to 10 grand wrapped up here.

  8. #38
    DIY Senior Member Bob999's Avatar
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    Quote Originally Posted by riverside67 View Post
    Bob,
    Considering the temperature rise requirements mentioned above, the typical 10 gpm and max 20 gpm hot water demands in the showers... would the two - 100 gal tank heaters be sufficient?
    Sizing is done on max reqirement that must be met and I am assuming that is 20 gpm for 20 minutes. Usable storage is 80% of total or 160 gal for your assumptions.

    Two 100 gallon tank heaters could be sufficient depending on the temperature setting for the storage--it clearly would not be adequate at 120F but with higher storage temperatures could meet your requirements. If you go that route I believe that you should include mixing valves to to reduce the temperature of the supplied water.
    Last edited by Bob999; 01-31-2010 at 07:26 AM. Reason: claritiy

  9. #39
    Water system engineer riverside67's Avatar
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    All I can say is...this is our dream, and we'll only do it once.

  10. #40
    Water system engineer riverside67's Avatar
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    Quote Originally Posted by Bob999 View Post
    Two 100 gallon tank heaters could be sufficient depending on the temperature setting for the storage--it clearly would not be adequate at 120F but with higher storage temperatures could meet your requirements. If you go that route I believe that you should include mixing valves to to reduce the temperature of the supplied water.
    Bob, do you still believe that a parallel tank setup would be better than an in series design?

  11. #41
    DIY Senior Member Bob999's Avatar
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    I would go with a parallel installation for two reasons--less flow restriction and (I think) an incrementally better recovery speed--and that means slightly more hot water for the 20 minute 20 gpm design point. With a series installation the second heater will initially see hot incoming water and will fire later.

  12. #42
    Water system engineer riverside67's Avatar
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    Considering I'll be using a recirulation system, how would I plumb the return line into a parallel tank setup scenario using one recirculation pump?

  13. #43
    DIY Senior Member Bob999's Avatar
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    I don't see any problem with plumbing the return line, which I assume will be relatively small, into only one tank.

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    In the Trades Akpsdvan's Avatar
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    Would that 1/2 line have a check/backflow valve so that there is only one way for that return water to go?

  15. #45
    Water system engineer riverside67's Avatar
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    Quote Originally Posted by Akpsdvan View Post
    Would that 1/2 line have a check/backflow valve so that there is only one way for that return water to go?
    Yes, the pump comes equiped with a check valve.

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