New build, how many pressure tanks?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by RHinNorCal, Nov 12, 2019.

  1. RHinNorCal

    RHinNorCal New Member

    Joined:
    Apr 30, 2018
    Location:
    North Bay, CA
    New construction, Well produces 45-50GPM @ 330 foot depth. piped to a s 2,600 gallon water storage tank. Well company is going to install a 10GPM submersible pump to keep the tank full.

    The water system is in the garage crawlspace, and will feed 3 buildings: a 2,500sf 3BR, 3 bathroom house; a 300sf guest house with a full bat; and a half bath in the garage. House is 150 feet from the garage, connected by a 2" PVC pipe; guest house is also 150 feet from the garage, with a 1-1/2" line; both are ~20' of elevation above the garage.

    Well company has proposed a single 82 gallon Amtrol tank, in the crawlspace of the garage. Plumber says he thinks this won't be adequate, and is recommending 3 separate pressure tanks (all in the garage crawlspace) : an 82 gallon tank for the house, and 30-40 gallon tanks for the other two buildings. A 2" PVC "manifold" would connect the storage tank to the 3 pressure tanks, with an appropriately sized booster pump feeding all 3.

    Plumber is working T&M, so he isn't making money on the tanks - but of course, will take some additional hours to install 3 tanks vs 1. I have the room for 3 tanks, but no idea if they're really needed, Would really appreciate some advice on this!
    Thanks,
    Rob
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    5 or 7 gpm may be a better choice. 5 gpm is 7200 gallons per day.

    More important is what pump will supply the pressure for the three houses. 15 or 20 gpm would be enough for that normally without irrigation. That would be called a pressure pump rather than a booster pump usually. With a 20 gallon pump, you would usually want 80 gallons or more total for the pressure tank(s). 60 gallons or more for the 15 gpm pressure pump.

    A 20 gpm submersible pump used as a pressure tank would be maybe 3/4 to 1 hp. I am not a pro.

    The pump-up float switch controls the well pump, and the pump down float switch would inhibit the pressure pump in case the big tank ran out of water.

    [​IMG]
     
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  4. RHinNorCal

    RHinNorCal New Member

    Joined:
    Apr 30, 2018
    Location:
    North Bay, CA
    California build, so sprinkler system required. Pump in water tank will need to supply at least 34 gpm to satisfy NFPA regs: simultaneously feed (2) sprinkler heads AND a bathtub. So with head loss over these distances, pump will need to be able to supply at least 45 gallons/minute at the tank. Not sure what this has to do with the pressure tank(s) though?
     
  5. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    The head loss does not increase the gpm needs, but could increase the hp needs a tad.

    When the pressure pump runs, you would like it to run for a minute or so to fill the pressure tank(s). The pressure tank(s) accept about 25% of their nominal size in water. So whatever the pump is, you might want a pressure tank nominal total about 4 x that gpm number.
     
  6. RHinNorCal

    RHinNorCal New Member

    Joined:
    Apr 30, 2018
    Location:
    North Bay, CA
    I think we're discussing 2 different issues. A single 80 gallon tank will hold plenty of water for our daily use - we will rarely hav more than 1 bathroom in use - and I am fine with the pump running in the event that we actually need to feed a fire sprinkler

    The question I don't have any understanding of is the benefit of 3 separate tanks to serve the 3 buildings, vs 1 tank that serves all 3. (But I don't have room for a 120 gallon tank, let alone the 160 gallon tank needed to handle "4x the pump size").
     
  7. WorthFlorida

    WorthFlorida The wife is still training me.

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  8. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    The proposal, as I understood it, was that the tanks don't each serve a particular building, but combine together to give the capacity to handle the one pump.
     
  9. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Without a Cycle Stop Valve three big tanks would be the minimum for a 45 GPM pump, and it would still cycle a lot. With a CSV one of the 80 gallon pressure tanks is all you need and the CSV eliminates the repetitive cycling that destroys the pump, tanks, and other parts of the pump system. The CSV works like in the video below, yours would just be a larger version of the CSV.

     
  10. LLigetfa

    LLigetfa DIYer, not in the trades

    Joined:
    Feb 6, 2011
    Occupation:
    Semi-Retired
    Location:
    NW Ontario, Canada
    Cary, the well is 45 GPM recovery. The well pump is 10 GPM and feeds a 2,600 gallon water storage tank I assume is non-pressurized hence the need for pressure tanks. I don't recall what pump feeds the pressure tanks.
     
  11. valveman

    valveman Cary Austin Staff Member

    Joined:
    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    Yeah I do these a lot. The well pumps fills the storage tank at 10gpm, and a 45 gpm booster is needed for the fire sprinklers. But this same 45 gpm booster also supplies domestic water which rarely uses more than 5 gpm. Without a CSV the pump will cycle a lot, and would still need 3 big pressure tanks.
     
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