New to irrigation... need help from pros

Discussion in 'Irrigation' started by Lawnworks, Oct 8, 2005.

  1. Lawnworks

    Lawnworks LawnSite Fanatic
    from usa
    Messages: 5,407

    I am trying to design a system for a customer. This will be my first install and customer is willing to give me a shot. The front yard has ditch. All of the systems I see around here do not have heads on the side of the ditch closest to the road. Is this acceptable? It seems coverage would be compromised. It seems trenching and getting pipe into a ditch to be near impossible. Also, how much overlap do I need? I am planning on using Hunter PGP and thinking of a radius of 25' t0 30'. The static pressure is 82psi and the water meter says 1x1, so according to Hunter the working pressure is 55psi. Is that correct? Any info advice is greatly appreciated. Please do not discourage me from taking on the job. Truth is I am really excited about irrigation endeavors, and I am trying to educate myself as much as possible on irrigation. Constructive criticism is also appreciated!
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    Read the entire site.

    Then disregard what he says about having to use a 3/4" nipple for a swing joint if the head has a 3/4" inlet.
  3. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    I am anti-barbed also. Can't count the number that have de-barbed and blown holes under sidewalks and drives.
  4. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    I've never had a barbed fitting come out on swing pipe...Are you using .700 tubing or something?

    I use Lasco Blue Twister MPTxBarb and Hunter swing pipe.


    Of course, on heads with 1" inlets (like the I-25 and larger) I use a rigid swing riser using a 1" sch 80 nipple and marlex ell's
  5. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496


    We spec out and use nothing other than SCH 80 nipple/Marlex swing joints on all sprinklers. The system with the barbed fittings was when someone else was in charge of inspection. They were put in and now we're paying for it. :dizzy:
  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    As Jon noted the irrigation tutorial site is a good place to start. (You might also visit the major sprinkler manufacturer sites like Rain Bird, Hunter and Toro as they have residential design information also.) There is a lot of valuable information on all these sites even if we quibble about some of those things here. We have our own likes and dislikes based on years of experience and the particular issues we run into. Most of us can look at a plot plan or stand on a piece of property and immediately visualize an entire irrigation system. This comes from years of education/experience that is not easily conveyed via written word on a site like this.

    DITCH: Are we to assume that there is a ditch between the front yard and the road? If this is the case design can be done if different ways. It is possible to put sprinklers near enough the ditch to water back towards the yard. They don't have to be right up against the ditch edge but you will get a bare buffer zone between the sprinklers and ditch. You can also install full circle sprinklers 60-75% of the radius from the ditch and allow them to water into the ditch. The trace elements of the radius shouldn't have much effect on the ditch but I'd check and see who owns it and what it's used for. They may not want irrigation water going into it creating moisture for weeds. It's also unclear what you mean about "trenching and getting pipe into a ditch."

    OVERLAP: It's best to design a system head-to-head where the water from one sprinkler meets the sprinklers around it. It is possible to design to only 80% or 70% of radius but it depends on your area and prevailing wind. If sprinklers are spaced too far apart and your average prevailing wind is sufficient enough the water pattern is not a true circle but will oval out. This will create coverage gaps and will show up on the lawn as bare/thin areas.

    SPRINKLERS: At the 25-30' radius I'd look at a different sprinkler. There are plenty on the market (Hunter PGJ, Nelson MP Rotator, etc) in both rotor and stream designs that only have a ½" inlet and use less GPM. You can put more sprinklers on an individual zone and use somewhat smaller pipe/fittings.

    PRESSURE: It appears that your pressure will be adequate for residential sprinklers. However, a simple dynamic pressure/GPM test would insure accuracy. Then each 100 feet of pipe, fitting, appurtenance (backflow preventer, valve, etc.)

    FLOW: You don't note how many gallons per minute you are receiving at the point of connection. You can have all the pressure in the world but without a volume of flow you can't even begin to calculate an irrigation design. In generalized terms 1" PVC pipe can safely carry between 12 GPM (SCH 40) and 16 GPM (CL 200) depending on the type of pipe you use. That means that no zone can exceed this maximum GPM. Exceeding the maximum GPM creates friction which translates to pressure loss at the sprinkler head.

    The information is out there. It's now your job to find/use it.
  7. jerryrwm

    jerryrwm LawnSite Bronze Member
    Messages: 1,274

    It depends on the ditch and how much turf is on the street side. Many times that part of the turf is in an easement and you can't put heads over there anyway. Depending on how deep the ditch is will determine how best to get the water over to the other side. It will probably mean hand digging and some creative pipe fitting, but it can be done. Otherwise you can water from the inside edge of the ditch over the ditch and onto the other side keeping the overspray onto the roadway at a minimum.

    With the PGP or any other rotor, if there is any significant wind at all (above 7 mph average) then it is recommended that the coverage be head to head. You can get adequate coverage at 60% of diameter of throw.

    Through a 1" meter the safe recommended flow is 30 GPM. This will have a pressure loss of a little over 5 psi. If you size the mainline accordingly (1-1/2") and keep the flow around 25 GPM you can expect to lose about 6-8 psi in the backflow device, another 5 psi in a 1" valve, and maybe another 4-5 psi in the mainline (depending on distance) and then another 4-5 psi in the laterals. At any rate you are going to have somewhere over 50 psi available at the bottom of the last head. More than enough to run the PGP or any other rotor head out there. (Probably just enough to pop that CR-500 up huh Bryan?)

    Hey, there will be some that will tell you that you have to work for a contractor for slave wages, and be an apprentice for five years, etc, etc, ad nauseum. And they are telling you not to install a system in anything but your own yard, and then other's tell you not to do that cause you'll screw it up. ANd you should hire a professional, like them to do the job, because they have been doing it for so long, and they are the ones that know.

    Well, I'm here to tell you this thing that we do called irrigation is not brain surgery or rocket science. The end result that we are all striving for is getting the right amount of water at the proper pressure to the last head on the system. That's it in a nut shell. The getting to that point is the difficult part. Knowing how to size the various components and how to efficiently put them together is what will make or break an irrigation contractor. And every one of them has their own way of doing things that work for them. One uses barbed fittings and funny pipe for heads, others use swing joints, many others use cut-off risers, and some still hard pipe under the head. Who's right? all of them. Some use threaded valves others use glue on valves and others use insert valves. Who's right? They all are. Some use PGPs, some use 5004s, others use Toro rotors. Who's right? They all are. (well, except Bryan because he uses CR-500 heads. ROTFLMSAO) I have often said, "I wish all the irrigators in this area thought like I did. Then my job as a repair technician would be so much easier." But it doesn't work that way.

    My point being this. Everyone of these irrigators all had to start somewhere, and that somewhere was with the first piece of pipe they put in the ground and the first head and the first valve. And if we all went around as a group and looked at each other's work, we would all say that we would have done this or that differently. It's human nature. We do things our way and look askance at how others have a tendency of screwing them up. While some started working as a laborer for another contractor, others started off like you are - out of necessity. So, learn all you can, ask questions of anyone that will answer, investigate all you can. And then there is nothing left to do but to do it. Sure you are going to make mistakes. That's part of learning this business. Everyone of us that has been in the business for more than 10 minutes has made some mistakes. WetBoots, Bryan, Hayes,
    Tony, Dana, Critical, Jon, me, etc. have all done some boneheaded things. But we learned from it and won't do it again. I can go back to the very first irrigation system that I installed in 1980 and I can see things that were done that I wouldn't think of doing now. But that damn little manual four valve system is still working today.

    If you feel confident in your abilities, and accept the responsibility of making things right for mistakes that need to be corrected at your expense, and the desire to install irrigation systems fits in with your business, then do it.

  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,749

    Hey! Include me out. Those weren't mistakes, they were innovations. Yeah, that's the ticket, innovations. :rolleyes:
  9. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    Amen Jerry. Some things we have to do based on what we come in contact with WILL be second-guessed when someone else digs it up in the future long after I'm gone.

    Technology also advances, some for the better and some not so good. When tooling around our district I see systems that we've installed and take pride that things look so good. However, I also know what's under the ground, mistakes I've made and had to rectify and awareness of newer technologies makes me think, "if they'd only had this product when we installed that system things could have been even better."
  10. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    Today's innovations
    were yesterday's mistakes.
    Good old "American ingenuity"
    that separates us from the apes. :D

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