New construction / help with main size

Discussion in 'Irrigation / Sprinkler Forum' started by John N., Jun 7, 2006.

  1. John N.

    John N. New Member

    Jun 5, 2006
    We are in the process of having a new home built on a 2 1/2 acre piece of land. The water supply at the street is rated at 95 psi per the water district. The main line will run about 200 feet up a mild slope to the house. The house is 3600 sq ft., and the plumbing contractor is installing Pex deticated lines to each fixture inside. We plan to irrigate pine trees that will be planted on the outer property lines, along with usual plants and grass in the interior.

    The question I need help with is if it matters what size the main is from the meter and if there should be a second dedicated line just for irrigation and sprinkler purposes. The contractor says he is going to lay a 3/4 inch main, and have it T off at the house for future sprinkler needs. I don't know if this is the most efficient way to handle the water issue, and if this configuration will give enough water volume.

    I would appreciate any help you professionals could give me on what would be the best size of main and the best way to insure that there will be an adequate supply of water for plant drip, lawn watering, and the usual interior house stuff. The home is now in the grading stage and I anticipate the trenching to be done in about 3 weeks. It is located in northern California in the Sierra Mountains foothills, and the elevation is such that freezing is not really an issue.

    Thank you very much for any assistance you can give.
  2. Bob NH

    Bob NH In the Trades

    Oct 20, 2005
    New Hampshire
    You should figure out how much demand you will have on the system, and size the pipe accordingly. It is hard to tell what the pressure losses will be without knowing the flow and inside diameter of the pipe.

    The difference in cost between 3/4" and 1" pipe should not be great. I would use 160 or 200 psi polyethylene with no joints except brass or stainless adapters at the ends.

    If you have a municipal sewer system, you should find out if they charge based on water usage. In my town you can put in a separate meter for outdoor use that is not also charged for sewer usage. They usually require a back flow preventer for outdoor connections.

    With a supply of 95 psi you will probably need a pressure reducing valve. You should make sure it is large enough. You will also need an expansion tank to prevent overpressurizing from the water heater.
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    I would consider 3/4 out of the question for a 200 ft run. At 14 GPM your pressure drop, and water velocity, are way above acceptable range. 1" would be minumum, and why not use 1 1/4" so that if the sprinklers are running at the same time as the washing machine , you will still be OK
  5. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Sizing water lines

    3/4" is not enough for that distance.

    at 200 feet, with a 3/4 meter, you get,

    3/4 line, 13 fixture units
    1" line, 30 fixture units
    1-1/4" line, 39 fixture units

    I know what 3/4 line was like at 250 feet. It sucked.

    I couldn't run an irriation (I meant irrigation) system with so little water by the time it got there.
    I replaced that line with two 1.5" lines.
    One for the house, and one for the irrigation system.
    That was much better.

    By all means, if you have a ditch, put in the "right" size pipes.

    Check out Table 6-5 on the link below.
    Last edited: Jun 9, 2006
  6. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    one inch pipe

    it dont matter what you put in above about one inch....

    the water company will probably put in a meter that will

    cut it down to under one inch anyway.....

    95 psi is pretty good pressure

    ask your plumber or fellow instaling the water service....
  7. John N.

    John N. New Member

    Jun 5, 2006
    Thank you very much

    Thanks to you all for your advice. I now have a little knowledge base when I tell the builder that I would like to upgrade the main size beyond what was bid by the plumbing contractor.

    Thanks again...
  8. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    200 feet is not far

    I am pretty sure that a roll of 1 inch black crestline poly pipe
    wont cost very much more than 3/4

    200 feet isnt really all that much of a run...

    I have at least 200 feet on 3/4 black crestline poly lpipe comming into my

    personal home with about 110 psi, and I got it kicked down with a prv

    valve to 75 lbs..

    I dont think I would worry too much about it.
  9. speedbump

    speedbump New Member

    Jul 15, 2005
    Water well and pump tech.
    Riverview, Fl.
    Use the 3/4" or better 1" for the house and drill a well for the sprinklers. Other wise it is going to cost you a fortune to water that 2.5 acres like you want to.

    For that matter, use the well water for the house and save a bunch of money.

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