Is it normal to use this much water all at once?

Discussion in 'Irrigation / Sprinkler Forum' started by Amy_2009, Aug 4, 2009.

  1. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Hi,
    This is a very broad ballpark question. We have about 18 rotary Hunter sprinkler heads for larger areas of our lawn and about 12 Rainbird static heads for smaller areas. Here's what the watering session looks like:
    6 rotary heads run for 35 min
    6 rotary heads run for 35 min
    6 rotary heads run for 20 min
    6 static heads run for 10 min
    6 static heads run for 10 min
    After the system is done running it uses over 3000 gallons of water in a single session. Does this sound right? This is about what we use during the entire month in winter!

    A gentleman who owns an irrigation company told us the system with these heads should use from 1800 to 2200 gallons per session. He didn't see the actual system, we just exchanged emails through a mutual acquaintance. He recommended inspecting our system for leaks or checking the seals on the heads.

    We checked for leaks, and didn't find any. The water meter stays still if the system isn't operating. If we leave the house and spend a few days elsewhere and no water is used at all, then our meter would stay on the exact same mark as we left it. There are no soggy spots anywhere in our lawn after watering it. So unless the leak occurs deep under ground during the 110 minutes when the system is actually running, and the 5-gallon-per-head average rule is correct, then 3000 gallons should be correct. Or is the gentleman right about 1800 to 2200 gallons?

    We can reduce the flow on all those heads to get it down to 1800 gallons, but then the lawn would receive very little water. Far less than recommended 1 inch. Actually it already gets a little less than that. What are we doing wrong?

    Thanks for your help!
    Last edited: Aug 4, 2009
  2. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Let G = gpm for each head, assuming static and rotary heads deliver the same GPM.
    6Gx35 min +
    6Gx35 min +
    6Gx20 min +
    6Gx10 min +
    6Gx10 min = 3000Gals

    Simplifying,
    6G(35+35+20+10+10) = 3000Gals
    G = 500 gals/(110 min) = 4.5 gpm.
    Each head should fill a 5 gal. bucket in 1.1 minute.

    Normal rainfall for me is 3"/month, ~0.1"/day. What area are you covering?
    3000 gals = 400 cu. ft. = ~1 acre to a depth of 0.1".

    Normal water usage per person per day is 100 gals.

    Hi, Amy. . .:p
    Last edited: Aug 4, 2009
  3. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Ok, thanks!

    About 13,000 square feet.
  4. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    12(400)/13,000 = 0.4" depth of water over this area, so in my neck of the woods you'd do this 3000 gal watering every 3 or 4 days.
  5. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Right, but does it sound likely that all these sprinklers CAN use 3000 gallons over 110 minutes? Or should it actually be using around 1800~2200 as the guy said?

    Sorry if I wasn't clear: the question wasn't how frequently should we water using the existing settings (although your info is useful, thanks!!), but rather "is the system really losing water because 3000 gallons is too high for that many heads over 110 minutes?"

    I'm trying to figure out if there's really a leak somewhere, or maybe he just quoted a lower number in hopes that we'll hire them to do the inspection, etc.
  6. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Your meter says there is no leak, at least when the system is off.
    Measure the outputs of the static and the rotary heads by filling a bucket. The math should work. If it doesn't, there is a leak when the system is on.
    With this many outlets, pick two or three at random for testing from the static group and the rotary group.
    Last edited: Aug 4, 2009
  7. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    Bottom line, either way you need a lot of water. If you have the option to drill your own well, you could pump water for a fraction of the price you are paying for city water.
  8. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Excellent idea, we'll do that. Thank you!
  9. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Yes, I know :( No such option for us unfortunately. Our friends out in the country have their own well and they water all day long.
  10. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Seems like the 3000 gallons pecils out as just about exactly the right number. That is right at 4 HCF, and here in San Diego, that woudl cost you about $30 every time you watered that golf course! Of course , the mayor would also publish your name on the website as a water guzzler!
  11. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Wow, that is high. Our rates are much lower here in Oklahoma. But (unlike San Diego?) once it gets hot here it stays hot for a while. So you either keep on watering and watering, or your grass starts to make crunching sound when you walk across your lawn.
  12. BRD

    BRD New Member

    Messages:
    53
    Location:
    northeast
    Amy,
    It could very well be correct. You should first check and see what size nozzle is in each head. Hunter nozzles have a number stamped in them. That number will correspond with a flow in gallons per minute at a specified pressure. If you have a idea of what the pressure may be at the base of the head you then would cross reference it on a Hunter sprinkler head chart and that would give you the approx. flow from the head. Then you need to do the math.
    Example:
    Lets just say each head , both spray and rotary has a nozzle that puts out 4 gpm at 45psi.

    zone #1 6 rotary heads @4gpm each x 35minutes = 840 gallons
    zone #2 " " " " " " " " = 840 gallons
    zone#3 6 rotary heads @ 4 gpm each x 20 minutes = 480 gallons
    zone #4 6 fixed spray heads @ 4 gpm each x 10 minutes = 240 gallons
    zone #5 6 fixed spray heads @ 4gpm each x 10 minutes = 240 gallons

    Add the total gallons up ( 2640 gallons ) and you can see that it is very possible to use that much water in one irrigation cycle. Now, this is just an example and your nozzle sizes may be very different from my example. If they are smaller and putting out less water then maybe you do have other problems in the system as far as leaks. A full circle spray head with a 15 foot radius puts out approx. 4gpm at 30 psi, so if they are half circle heads then the output would be approx. 2 gpm. You could have a mix of nozzle sizes based on their arc, weather it is a quarter circle, half or full cirle head. If you like, provide the brand and model of the rotary and spray heads and if possible the nozzle sizes and I can check the charts.
  13. Amy_2009

    Amy_2009 New Member

    Messages:
    7
    Wow, thanks! Lots of interesting info. I'll get those numbers today. Thank you!!
  14. tomm

    tomm New Member

    Messages:
    41
    You need an Irrigation Audit. Where do you live? Send me a plane ticket and buy me a couple rounds of golf and I'll have your answer! :D
Similar Threads: normal much
Forum Title Date
Irrigation / Sprinkler Forum is it normal for water sprouting out from the sprinkler valve vent Jun 11, 2011
Irrigation / Sprinkler Forum water pressure drops when changing zones and wont come back up to normal Jun 15, 2007
Irrigation / Sprinkler Forum Should valves leak water when used normally? Jul 4, 2006
Irrigation / Sprinkler Forum Normally closed PSR? Apr 7, 2006
Irrigation / Sprinkler Forum How Much Water??? Jan 12, 2009

Share This Page