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Pressure Loss with Spray Heads

Discussion in 'Irrigation' started by Dually Driver, Oct 26, 2007.

  1. Dually Driver

    Dually Driver LawnSite Member
    Posts: 13

    I have a problem with extreme pressure loss. I am using Rainbird 1800 Heads with Van adj nozzles. There are 7 heads on a Zone with a DVF Valve. The pressure at the water source without any valves being open is 63PSI and the pressure at the bib with a Zone open is 45PSI. The pressure at a head is 18PSI.
    This is with 3/4" PVC Sch 40. The nozzles require 30PSI to operate efficently. I tried Rainbird R17-24 rotorys which only require 20PSI to work effectively, but I could only get between 16 and 18PSI at the heads. Would increasing the pipe size to 1" do it or would decreasing the pipe size to 1/2" do it. Does anybody out there have any ideas or answers ???
  2. Van nozzles are water hogs....search mprotators........
  3. Dually Driver

    Dually Driver LawnSite Member
    Posts: 13

    Mp Rotators require 25 PSI versus Rainbirds which require 20PSI
    With (1) Rainbird R17-24 Nozzle installed in place of (1) Van 18, I did pick up app 2PSI at the Zone. If I changed them all out I might get more effective PSI, but the precip rate is less than half of the Vans. I am trying to get away from longer run times.
  4. If you use less water you will have greater dynamic pressure at the heads.....

    Mprotator have an average precipitation rate of .4-.5 per hour.

    18 vans use in the 3 GPM range...vs a mprotator 3000 is 1-2 GPM...
    Only real fix is either rework entire zone with correct pressure and flow calculation or mprotators
  5. Only other thing I can recommend is replace the Dv-100 diaphragm because if it is a old diaphragm, then it will no longer allow complete flow...good luck..
  6. hoskm01

    hoskm01 LawnSite Fanatic
    Posts: 5,690

    I agree. Are most of your nozzles on the zone 360s, 180s or what? I think your underlying problem is not in the nozzle or head, but at the valve or further up. Need a service call?
  7. Dually Driver

    Dually Driver LawnSite Member
    Posts: 13

    The zone consists of (5) 360 and (2) 180. In my brochure the MP 3000 show 2.88 GPM at 25PSI The Van 18 shows 4.21 at 15PSI Both at 360s The Van 18 shows 2.07 in/h and the MP 3000 shows .44 in/h The MP 2000 shows 1.16 GPM and also .44 in/h. If I changed out the heads to MP 2000 or 3000 I should only need about half the GPM. I would have to run I am presently running at 5min and it gives me 0.175 in/h To get the same precip with the MP 3000, I would have to run about 22min. These comparisons are for the 360 Nozzles. The DVF Valve is New.
  8. I'm assuming you are thinking online. replace the nozzles with MPs and see how it works. Yes you will have to increase the run times. In reading your original post it sounds like the pressure loss calculations were not done or you would not be struggling with this problem now. Also decreasing pipe size does not increase pressure. I red lined some sentences that jump out at me. It sounds like this is a one size pipe only system. Without knowing where and how you tied in, backflow used, spacing, etc. Our ability to help is limited.
    If you have 15' spacing MP 3000 are not necessary. MP1000 and/or MP2000 would be a better solution.

  9. hoskm01

    hoskm01 LawnSite Fanatic
    Posts: 5,690

    Fimco is dead on... Changing pipe size wont change pressure, only flow maybe, but 1/2" is plenty big to take enough water for a 360 VAN. The question still is, what is hindering the source from supplying sufficient flow/pressure to the head?

    Save yourself the trouble or expense, go with the MP's and it is a quick do-it-yourself.
  10. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    I agree, sounds like poor design, however considering the number of sprinklers, I would be asking myself

    where the heck 45 PSI is going.

    I mean geez, 45 PSI is the pressure leaving the valves on many of the systems I manage around here, with nary a problem running 7 heads with the right nozzles.

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