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Flow problems or not

Discussion in 'Irrigation' started by P.I.L.C., Oct 30, 2004.

  1. P.I.L.C.

    P.I.L.C. LawnSite Member
    Posts: 48

    I am going to install a new system next week. The homeowner hired his own plumber to stub out for the sprinkler system. The problem is that he did not tap off after the meter (5/8). He tapped off about 75 feet away where the wall hydrant goes out. The wall hydrant is 3/4" all the way from the meter, T'd off the 3/4" with 1", then put his shutoff and drain. Guessing about at least a dozen different elbows that it goes through to get there. Am I safe to design this system at 13 gpm or am I going to have my own plumber come in and redo everything? The mainline coming in is 1" copper and the pressure is about 60 psi. Any suggestions?
  2. Instant Rain

    Instant Rain LawnSite Member
    Posts: 54

    this is an easy flow test to find the available flow. after you have determind that you gauge is accurate. Build a 1" tee with a male adapter coming off one side, and a garden hose adapter from the other side and a one foot length of 1" with an adapter for your pressure gauge. get five gallon bucket. open the hydrant all the way put the bucket under the hose end and time the amount of time it takes to fill the bucket. if it takes twenty seconds you know you are flowing 15gpm. ten seconds would be 30gpm, thirty seconds would be 10gpm you get the idea. the pressure gauge will show you the operateing pressure at that flow. this will give you pressure losses in the piping leading to the hydrant. the longer you make your length of pipe to your pressure gauge the more accurate the reading with in reason. you will probably find you have more than enough pressure. I recomend a pressure reduceing valve as a master valve and an 1 1/2" mainline to slow the water and reduce the chance of water hammer.
  3. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    Shouldn't be a problem @ 13 GPM, 4 rotors/zone. Given that you are using 1" from that point on and that the pressure maintains 60 psi, in my area it goes from 60 static in the fall to about 45 static mid-summer . Bottom line is you can always change out the nozzles to 2.5 GPM, not the best way but better than eating a new tap.
    I can't stand doing jobs like this so I would probably price it the same as if I had to do the tap, just in case.

    Best of luck,
  4. jerryrwm

    jerryrwm LawnSite Bronze Member
    Posts: 1,274

    Why would you use a PRV with a static pressure of 60 psi, and why a 11/2" mainline for a flow of 13 gpm? Water hammer occurs in every situation when a valve closes. Industry practice recommends flows of not more than 5 fps. A properly glued joint will withstand the effects of water hammer fine at those rates. 1" SDR-21 at 13 gpm has a velocity of about 3.7 fps, well under recommended values.

    The question also raised about the 3/4" supply. Is it copper or PVC? If it is K copper, you could run the zones at 13 gpm, provided you size the rest of the system properly. Industry standards recommend velocity in copper of 10 fps or less. At 13 gpm the velocity is around 9.6 fps with a pressure loss of approx 23 psi per 100'. So if it is 75' you have lost 17.3 psi. Take that from your static and you still have 42.7 psi left to work with. Assuming the heads require 30 psi, you have 12.7 psi for system losses. With 6.0 psi loss through a 5/8" meter you are down to 6.7 psi left. It might be better if you decreased the size of the zones to around 10 gpm or so.

    If it is PVC then you might have an issue with velocity and may need to have a seperate tap made.

    At some point oversizing pipe becomes ineffective because the pressure retained at a given flow is out-weighed by the extra cost of larger pipe and fittings. And a 5/8" meter is recommended to have flows no higher than about 12 - 14 gpm. So at that point it becomes useless to use anything bigger than 11/4" at the most and usually 1" will suffice.

    Just my thoughts,

  5. P.I.L.C.

    P.I.L.C. LawnSite Member
    Posts: 48

    The inside pipe is copper, and then we run copper to the PVB (1"), and copper out of the PVB into the ground where it switches to poly. Around here we usually use 1" 80psi poly through out the whole system. No pipe sizing until we get on a commercial job. I planned on running 5 rainbird 5000 series rotors with 2.0 nozzles for a total of 10 gpm on the rotor zones. Stay at 5 or go down to 4?

    Thank you everyone for your help!!

  6. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    4 rotors/zone. Nothing worse that finishing an install and watching the water pee out of the heads. Better to throw in the extra valve now than try and go back over your work later.

    Best of luck,
  7. Rotor-Man

    Rotor-Man LawnSite Member
    Posts: 126

    Did a install similar to yours last year. The meter was a 5/8's, and psi was around 55 psi, problem only way to stub to the outside was about 60' away from the water meter. Designed the system with a max. of 3 rotors per zone [3] with 2 zones having 4 zones and 2 zones with 6-7 sprayheads. Works great and nozzles are proper for the right precipation. I myself never design a install with a 5/8" meter at over 12 gpm per zone, assuming fluctuation in pressure in the neighborhood and peace of mind when I "Fire" up the system.
  8. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    To be honest I would probably " abandon " the tap the HO had installed and run a new one to 1" copper next to the meter. Sounds like too much bull s**t for something that should be a " no brainer ".

    Best of luck,
  9. aquamtic

    aquamtic LawnSite Senior Member
    Posts: 303

    As "Active"... mentioned. The plumber should of followed uyour instruction on to how to install the tap. I always give my customers the option of hiring thier own "licensed" plumber but that I need to spec the installation.

    You should not be wasting time trying to figure out how to make it work . You should just request that it needs to be done a certain way and thats it. You will get a little grief from the plumber saying that where he tapped in that it wont make a difference. Its easy for him to say because he will not have to live with the problems like yourself.
  10. Ground Master

    Ground Master LawnSite Senior Member
    Posts: 505

    how far is the meter from the street connection?

    i.e. if the meter is 50' from the street mainline connection, you'll have 125' of 3/4" copper to deal with (50'+75').

    thats way too much for 13gpm.

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