Convert propane tank to water pressure tank

Discussion in 'Irrigation / Sprinkler Forum' started by jhv, Jun 25, 2008.

  1. jhv

    jhv New Member

    Jun 25, 2008
    I have 1.5hp lawn pump that I use to pull water from a lake for watering. I would like to put a pressure tank on the pump so it will shut off automatically when water is not being drawn to eliminate burn-out. Can a 20 lb propane tank be converted for this use? What additional parts would be necessary?
  2. rombo

    rombo New Member

    Mar 30, 2008
    nope it can't be used. Just go buy the proper tank they aren't to expensive
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    A pressure tank needs to have a bladder.
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    Nov 23, 2006
    disabled-retired industrial fabricator
    200 miles south of Little Rock
    You could run a tee off your pressure line to go to an upside-down 30 or 40 lb. propane bottle, then use another tee with a shrader valve to actually make the connection. With no pressure in the system, pressurize the tank to about the same as the low setting of your switch, then start the pump.

    The problem will all of that, however, is that the tank would soon become waterlogged and you would have to drain it and re-pressurize it quite regularly. So, your best bet is to go get a regular bladder tank.
  6. jhv

    jhv New Member

    Jun 25, 2008
    Sizing pressure tank

    Thanks for the feedback, sounds like time to go buy a pressure tank.
    What is the size tank I would need for the following:
    pump - 1.5 hp
    lift from lake - 8 ft.
    elevation push from pump to sprinklers - 35 ft.
    6 sprinklers with output I estimate @ 2 gpm each
    distance from pump to sprinklers - 150 ft. max

  7. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    The correct answer to your question depends on WHICH 1.5 HP pump you have.

    If you have a 1.5 HP centrifugal that is often sold as an "Irrigator" or irrigation pump, and you are using 6 sprinklers that use 2 GPM each, then you would need a big tank to be effective as a storage unit.

    If you are using a 1.5 HP shallow well jet pump it might be ok if you set the pressure switch high enough.

    You should be looking at the pump curve, which is a graph of pressure on the vertical scale and GPM on the horizontal scale. Go up from 12 GPM and see what pressure that gives you.

    What you should really be doing is looking at that curve to determine what the flow.

    The Goulds GT15 is a 1.5 HP "Irrigator" pump and will deliver 25 gallons per minute at about 30 psi for your suction lift and sprinkler elevation condition. It is really about a 40 GPM pump, and while it will operate at 12 GPM the pressure for your system may not be satisfactory. Most other 1.5 HP irrigation pumps have similar characteristics.

    If you have a jet pump it will be better match to your 12 GPM and pressure requirements.

    If you are operating the pump solely for irrigation (watering the flowers with a hose and a nozzle that is being turned on and off is not irrigation) you probably don't need a pressure tank or switch. Just make sure that there are no shutoff valves in the line and turn on the pump when you need water.
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