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WORM

New Member

1

Friday, July 31st 2009, 3:16pm

Number of heads per zone based on gpm and psi

I am wanting to know how many heads would be optimal to use based on gpm and psi. My psi is about 50 and 16 gpm. I am considering using rainbird 5000 series rotors. My design is for 30' spacing for head to head coverage. MY Rainbird design calls for 8-10 rotors per zone but, talking to local landscapers they use only 4-5 rotor heads per zone. What do you think. Thanks

worachj

Advanced Member

Posts: 61

Location: Eagan, Mn

2

Friday, July 31st 2009, 6:11pm

You really need to look at nozzle performance charts to determine how many heads you can have per zone. If you have static psi of 50 at your house, you won’t be getting that at the heads; more likely closer to 30-35 psi, I would stick to 4-5 heads per zone. Look at the nozzle performance charts and add up the GPM’s to determine how many heads per zone you can use, and design to the lower limits of your design to leave room for error.

http://www.rainbird.com/landscape/products/rotors/5000.htm

WORM

New Member

3

Saturday, August 1st 2009, 8:42pm

Number of heads per zone based on gpm and psi

Looking at the charts, with 35 psi using 1.5 nozzle I will have a spray radius of 34'. The flow rate is 1.35 gpm with a precipitation rate of .22 in/h. Using the 1.5 nozzle with 5 heads I would only be using 6.75gpm. That is half of what my gpm flow rate is. Do you think 5 heads per zone still be the way to go. Also I am planning to use poly pipe it looks like 11/4" has a lot less friction loss would you use 1 1/4" or stick to 1". Thanks for the help

worachj

Advanced Member

Posts: 61

Location: Eagan, Mn

4

Sunday, August 2nd 2009, 8:59am

My preference is to use nozzles that throw more water so you don’t need to water as long. Do you really want to run a zone for 1 hour to put down .22 inches of water? Do you want all eight heads to run for 1 hour? If your system has five zones that’s five hours of run time. More zones give you more control of wet/dry spots.

Do you have heads that throw at different degrees? Remember for even water distribution you want the GPM’s of the heads to reflect the radius and degree of the head. For example, if you have all heads of a zone throwing 30 feet radius you would want nozzles with GPM’s to match the degree being used.
90 degree at 2.00 GPM
180 degree at 4.00 GPM
360 degree at 8.00 GPM

I would stick to 4-5 heads per zone; it will give you more control and better options.

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