How long should I water for?

Discussion in 'Irrigation' started by Gabby, Jul 4, 2010.

  1. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    Click on the charts tab

    BTW, unless the rotors are all the same arc ... they should not be all the same nozzles. Example, you should not have the same nozzle for a 90 degree arc (say a red #4) as you would for a 180 degree arc (would probably be best with a red #7 or a blue 3.0).
    Last edited: Jul 8, 2010
  2. Gabby

    Gabby LawnSite Member
    Messages: 140

    Kiril, thanks I just found the same link. So at 50 psi the PR is 0.4"/hr. How does different nozzles affect flow rate. Is there a place to look that up? By the way where do you see what nozzle #you have on each head? I did not look closely but I remember looking at one of them, can remember if it was 90, 180, or 360 degree arc head and the nozzle was red. Where do you see the size #? Again thanks.
  3. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    Please read the fine print at the bottom of the table.

    Nope. That table is it.

    The reds are printed on the front of the nozzle, upper right corner I believe.

    With respect to the arc ... PGP's come in two flavors .... adjustable and full circle. If not full circle, the arc will depend on what it was set at when installed. Problem is, some installers do not understand how to nozzle a PGP correctly (or any rotor for that matter), so it would be best if you verify they are nozzled correctly.
  4. Gabby

    Gabby LawnSite Member
    Messages: 140

    Oh crap I did not see the table. I was looking at the specification tab where it says "Precipitation rates: approximately 0.4" (10 mm) per hour at 50 PSI". OK let me look at the "chart" tab. Thanks!
  5. lawncuttinfoo

    lawncuttinfoo LawnSite Bronze Member
    Messages: 1,010

  6. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    I couldn't bear to read all the posts. Hunter has a publication "Scheduling Irrigation". P/N 700278, or Lit 088.pdf.

    I say misinformation because the rule of thumb 1"/wk has absolutely no scientific basis behind it. What matters is the evapotranspiration in your climate, the precipitation rate of the system, and the month of the year. Sure we can talk about uniformity, efficiency and crop coefficients, but the basic premise of irrigation is this keeping the soil fully hydrated. When mother nature does that no one is concerned about any info.

    In my area, southern NJ just east of Philadelphia, we're warm humid to warm dry by Hunters potential evapotranspiration rates. That is we lose between .15" and .25" of moisture per day. Our peak moisture demand months are June and July.

    I figure we need about .2" of water per day to stay even, and knowing the precipitation rate of the systems I build, I schedule accordingly. I like my rotors to deliver at least .4"/hr and I do use matched precipitation rate nozzles. So in June/July our rotors need to run about 3.5 hrs per week, delivering at least 1.4" of water. The schedule works flawlessly.

    We are now install the Hunter Solar sync on all new systems to manage the run times. They are easy to set up and reliably change the run times via the seasonal adjustment on the controller on a daily basis.

    For us our percent of peak moisture useage looks like this.

    Apr 55%, May 80%, June, July 100%, Aug 85%, September 65%, Oct 35% and Nov 20%. So when it's recommended to water new seed in late summer and fall, 2 or 3 times per day, real seasonal need must be factored in or the seedlings could drown or dessicate.

    This publication also has the moisture holding capacity of various soil types. Sand only holds a useful .75" in the top foot of the soil profile. By watering 1" per week we would be in a deficit situation in our 2nd week and the turf would stress and decline if it were June/July.

    Loams and silt loams hold 2"-2.25" of water and by adding an inch per week wouldn't stress until the 3rd week. Clay soils loose holding capacity because they are so fine and tightly packed there is not as much room to hold water, and the water is more tightly held to the smaller soil particles. They are better than sand, but not as good as loam.

    Lastly the matter of what time of day to water and how many times per week. Rutgers University says midnight to 8am is the best water window. We find it works and no it doesn't "cause fungus" or create conditions favorable for fungus.

    I defy all advice and water 1 time per day, aiming to replace lost moisture. I have done this for 12 years and love it. I've dug holes and pulled soild samples to see the root penetration in my lawn. 18" roots and moisture all the way down, It works! All that needs to be done with irrigation is start watering before stress occurs and the moisture reserve is depleted.
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,369

    What do you see in those infrequent periods when the water table starts dropping, and the subsoil near the surface starts drying out? I'm not sure a weather sensor is going to help all that much.
  8. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    No Problem! Last year was very, very dry for a long period of time as were 2 yrs back to back a few yrs ago. Everything keeps on growing. I had a gas line brought to my house during this years dry spell. Their big Ditch Witch really had to labor to pull the 2" pipe along the road.

    In my lawn they had to dig 3 ft in a couple spots to cross phone and irrigation and the moisture was there.
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,369

    I had a few calls where someone griped about uneven coverage, and it almost always is about someone being too cheap to run the sprinklers long enough, or even worse, watering every day for half the original programmed time.
  10. ZX12R

    ZX12R LawnSite Senior Member
    Messages: 795

    Great post! I cannot tell you haw many time I am asked,"whats wrong with my lawn?". Its always after the onset of our first hot spell every year. I tell them to water more and they say,"the sprinklers are on every day". I tell them to up their times or have their sprinkler guy put in bigger nozzles if they can. Thye look at me like I am an idiot.:rolleyes:

    On the other hand,I have clients that water like crazy starting before the real hot weather.Sure,their plants grow like crazy and they need to be pruned more often,but their lawn looks beautiful . Its not rocket science.The lawn will tell you when it needs water,just pay attention and make adjustments thru the sprinkler system.

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