Question for Irrigation pros

Discussion in 'Irrigation' started by ZX12R, Sep 28, 2005.

  1. ZX12R

    ZX12R LawnSite Senior Member
    Posts: 787

    I am a landscaper and do NOT provide irrigation installs,however,I am going to do one for my house later in the fall.I have done much reading,including the tutorials reccomended by some of you here.Everyone seems to agree that bigger is better when it comes to water and main lines,so,heres my question? By the way,I have 55 pounds of pressure and 9 GPM flowing thru 3/4" line. I was thinking of installing a 1 1/2" main line with 1" lines going to each zone? There will be 6 zones. Your opinions will be helpful ,so,thanks in advance!
     
  2. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Regardless what size lines you put in after your POC (point of connection) you will only get the 9 GPM that the 3/4" pipe is supplying. Keep all zones at/under 9 GPM and you should be fine. What the increasing of the main and laterals will do is reduce friction in the pipes which ultimately reduces your pressure at the sprinkler heads. Personally I wouldn't size the main/laterals any bigger than 1" (unless you have a very long run) because you really won't gain much other than higher price of pipe and fittings.

    :cool2:
     
  3. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    What size lot? What are you going to be covering as in using sprays or rotors?
    Where is your pressure coming from? well, city water at House spigot, off main?
    If you are coming off a city main with a 5/8" meter then I see no need to go with 1 1/2" mainline for sprinkler. Use 1" main and 1" lat. all 6 zones. until I can see schematic with elevation rise or drop I would be guessing in the wind.
     
  4. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    I hardly ever see a 1 1/2 main for residental use unless it is acre/s usually 1".
    Rereading your post I would probably just stick with strait 1" period. Make it easy on yourself.
     
  5. ZX12R

    ZX12R LawnSite Senior Member
    Posts: 787

    I realize I will get no more than the 9 GPM I am getting now. I figured with bigger mains,I would have a larger supply of water to feed from. Tme main line will be 200 feet long.Is this correct?
     
  6. ZX12R

    ZX12R LawnSite Senior Member
    Posts: 787

    I have city water with a 3/4" meter.Property is flat and main line will be 200feet long. I will be using sprays.
     
  7. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Your statements contradict each other. The 9 GPM is your supply of water and a large main won't increase your amount (give you any more water), just slow the water down (not loss of PSI) decreasing friction so decreasing PSI loss at the heads.

    All systems are based on "worse case scenario" sprinkler heads. The head that has the combination farthest/highest/most fittings (PSI loss) between it and the source. You design to this one head and if it pops up and works correctly then all other sprinklers in the entire system will work properly.

    200' CL 200 or SCH 40 pipe with fittings is negligible pressue loss. Pipe is always calculated on friction loss per 100' of pipe anyway. Most home-type sprinklers work based on 40 PSI at the head and 55 PSI is yout static pressure not your working/dynamic pressure (PSI when the water is flowing which is less than static because friction is now occurring). However, you should be fine by bumping up to a 1" main and laterals. Just use the 1/2/3/4 formula for 15' spray popups and you'll be fine. (1 GPM for quarter heads; 2 GPM for halves; 3 GPM for three-quarter head; 4 GPM for full circles) ANY combination of these heads on one zone CAN NOT exceed your 9 GPM total for a single zone. (i.e. You will NOT put 3 FC heads on a single zone because that comes to 12 GPM which exceeds your 9 GPM supply.) If you use a different type of sprinkler then you will have to look at the info supplied with it to determine its GPM use at a particular PSI at the head. You can also consider something like an Nelson MP Rotator stream rotor head on a spray popup body. Very low GPM per sprinkler so you will have to run zones longer.

    Hayes :cool2:
     
  8. Aran

    Aran LawnSite Member
    Posts: 13

    PurpHaze is bang on listen to what he says! :rolleyes:
     

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