Gravity Fed Garden Hose - How High Should The Water Tower Be?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by bhoen, Jun 13, 2011.

  1. bhoen

    bhoen New Member

    Messages:
    1
    Location:
    New York
    this is a very novice question I suspect

    I am helping install a 120' x 60' garden at my local k-5 school at a site where they do not currently have water. We were planning on building a water platform where a 500 gallon tank would sit which would feed water through a hose for the garden to use. (The tank would be filled via rain water collected on the roof above it and via pump as needed. Long term we will connect to the schools water.)

    Assuming we will have a run of hose no longer than 100', could we get away with having the water tank on a 6' platform?

    I assume the biggest question is how slow will the water run out of a hose like the one I envision. Given the set up, any idea how long it will take me to fill a gallon bucket? What sort of pressure to you need to have a hose sprayer work? Will the system generate that kind of pressure?

    Thanks for any advise you have. Frankly I do not know where to start with this one.

    Ben
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,841
    Location:
    NW Ontario, Canada
    Rounding off, 25 feet will give you about 15 PSI so working on multiples of that, 75 feet would do it.

    Edit... OK, I was a little off... each foot of rise equals about .43 PSI so 25 feet would be closer to 11 PSI.
    Last edited: Jun 13, 2011
  3. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,142
    Location:
    South*East
    You will get .43 PSI per foot of rise. At 6' that will give you a little over 2.5 PSI

    John
  4. TJanak

    TJanak New Member

    Messages:
    154
    Location:
    South TX
    Gravity feeding from a cistern is more about volume than pressure. At the minimum I would use a 3/4" hose because they come with regular hose connections on the ends. But ideally I would go with 1" or larger.

    To operate a sprayer I would think you need at least 15 psi.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    Your limitations mean you cannot have a "sprayer system". Use drip heads or a soaker hose which is less pressure dependent.
  6. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    Seems to me you are going to a lot of work for nothing. You say you're going to connect to the school's water to supplement the rainwater, so you will have to trench and lay pipe anyway, so why not install a backflow preventer at the connection to the school, run PVC pipe to the garden area and do the whole job without messing with a cistern or storage tank at all?
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    You will need a pretty impressive platform to get 500 gallons of water 20 to 30 feet in the air!1
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,304
    Location:
    Cave Creek, Arizona
    quote; 500 gallons of water 20 to 30 feet in the air!

    And a tall building to have the water run off the roof into the tank.
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