Designing my own irrigation system

Discussion in 'Irrigation' started by F6Hawk, Feb 9, 2005.

  1. F6Hawk

    F6Hawk LawnSite Member
    Posts: 195

    Is there a good information source to visit for details on installing my own irrigation system? Besides this forum, I mean, which seems to have lots of experienced folks. I would just like to nail down the basics before I start asking a lot of questoins that can be answered with online reading.

    My intention is to have a second meter installed ($275 from the city), and probably run 1" or 1-1/4" main line to the valves, then 3/4" for the laterals, unless 1" would be better. Pressure here is good, I am guessing 60-65 psi without measuring. The front yard is 3 different sized rectangles, so no complicated layout for me.

    Is there a particular brand(s) you recommend, should I install a rain switch, what sort of backflow preventer (the lady at the city desk told me the meter has one already, but wasn't sure if she knew what she was talking about or not). Questions like this are what I am desiring to answer.

  2. Ground Master

    Ground Master LawnSite Senior Member
    Posts: 505
  3. F6Hawk

    F6Hawk LawnSite Member
    Posts: 195

    Wow, great amount of info, I appreciate it. At the risk of sounding like I am whining, it looks to me like it will be harder to plan the darn thing than it will be to actually dig & install!

    Is it really necessary to go thru the calculations for pressure and flow if one is on city water with good pressure, or is that geared towards low pressure/well-type applications? I understand the head-to-head coverage thing, I thougt it would be as simple as picking a pipe diameter, drawing up a plan that provided good sprinkler coverage, then putting it all down.

    And perhaps I didn't get far enough (there was a LOT of data at that site!), but I didn't see recommendations on brands or types of sprinklers.

    Thanks again!

  4. Randy J

    Randy J LawnSite Bronze Member
    Posts: 1,124

    You want to determine flow and pressure so that you know how to zone your heads. For instance if your hookup flows 18gpm, you can add heads together until you get to 18gpm, but you don't want to go higher or your coverage will suffer. Remember to zone like heads togoether - don't put heads in the sun with heads in the shade, etc.
  5. F6Hawk

    F6Hawk LawnSite Member
    Posts: 195

    I understand that, but it seems to me that you won't get a TRUE flow rate until you have most of the equipment in place.... For example, I can measure flow rate at the meter, but it will drop wherever the pipe size goes down, and again as it passes thru the solenoid valves, etc. So the only way I see to get a true flow rate is at the sprinkler head. Of course, pressure will be the same regardless of where you measure it, given a static system.

  6. Mdirrigation

    Mdirrigation LawnSite Silver Member
    Posts: 2,642

    The flow rate and pressure in Feburary are not the same as in July , always size your system to operate properly at a lower figure.
  7. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Yes, the static pressure will be the same, but what you're asking about is dynamic pressure. Check your static pressure and then enter the factors that will affect your dynamic presure, such as elevation change. Dynamic pressure will change with elevation, approximately .5 psi per foot elevation. A loss going up, gain going down. Also, you should figure the psi loss per size and type of pipe that you use. For example, 1" schedule 40 at 18 gpm has a loss of about 7 psi, and the flow rate of the water through it will be slightly less than 7 feet per second (getting into the red zone for that much water flowing through that size of pipe). You will have to figure in the loss through the meter and the backflow device as well.

    Many of the main brand irrigation companies, like Rainbird or Hunter, have charts and reference data at the back of their catalogs - probably on their websites too. Just remember, the less math and planning you do on this, the more of a chance that it'll get screwed up.
  8. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,207

    Go to home depot and get the forms for Toro design. You send them a plat of your property with the house and trees and sidewalks drawn in and they will send you a plan. Understand that they probably overdesign it but you can decide if you want to change any of it. You have to measure you water pressure and flow rate and put that in the information. The information they provide includes everything you need!!! And it is free.
  9. F6Hawk

    F6Hawk LawnSite Member
    Posts: 195

    Thanks, I was just doing similar on the rainbird web site. But according to the link above (Jeff Stryker), measuring the flow with a bucket is NOT the way to go, yet rainbird says to do it that way. Go figure...

    I'll see what our local Lowe's has, but I have my doubts... this has to be THE worst Lowe's known to mankind!
  10. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    The very first irrigation project that I did prior to getting into it professionally was by using the Rainbird's homeowners form. It was a fairly comprehensive plan, but didn't account for everything, such as correct pipe sizing - for some reason. If I knew what I know today, I would have done a few things differently. Unfortunately, I can only blame myself for not having boned up on the subject a bit more.

    By the way, the backflow device at the meter will protect other people from stuff like fertilizer flowing back into the water main, but it isn't going to protect you. That's why I always install devices on irrigation lines.

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