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1

Monday, October 8th 2007, 11:10am

Planning Stages of Installation

I’m planning to install an irrigation system and need some information regarding pressure and filtration. I will be running the system off a well and bladder tank. The tank is currently set-up with a 30/50 switch (pump turns on at 30 PSI and off at 50 PSI). The water feed is ¾” polly. I’m planning to use Rain Bird 5000 Series Rotors and 1800 Series Spray Heads. To complicate things, I have some sediment (I think rust) issues which cause clogging with my portal sprinklers. That said, I’m planning to put a filtration system on the front end to mitigate and issues in my new irrigation system. My questions are...

1. Is my selection of Rain Bird a good one?
2. Is ¾” feed at 30/50 PSI adequate to run the system – assuming I establish proper zones and number of heads?
3. Will the filtration system impact my pressure?
4. Are there any filtration systems out there that you recommend?
5. Any other ideas or thoughts are welcome…

Thanks in advance!

HooKooDooKu

Supreme Member

2

Tuesday, October 9th 2007, 10:57am

While I'm not going to say that it won't work, the words 3/4" feed, 30 PIS, and Rotors just don't seem to go together.

A rule of thumb I've read about at www.irrigationtutorials.com is that for rotors, you need 10PSI of pressure at the heads for every 10ft of throw you expect from the rotors. That means if you are designing for rotors to throw 30ft, then you have to have at least 30psi at the heads after accounting for pressure losses through filters, valves, and pipe friction losses.

3/4" polly sounds too small on multiple fronts. First, 3/4" polly would limit the total output flow rate of the system to 8gpm. Otherwise you will violate the 5ft/s speedlimit plumbers should observe when sizing pipe. Additionally, your pressure losses might be too much. At 8gpm, 3/4" polly will have a pressure loss of almost 6psi for every 100' of pipe. But 1" polly will have about a quarter the pressure losses for a given flow rate (i.e. 1" polly at 8gpm has a friction loss of a little more than 1.5psi for every 100' of pipe).

3

Tuesday, October 9th 2007, 12:21pm

My current set-up is as follows...

- I have 1" poly going from jet pump in well to a "T" connector
- From one end of the "T" it is 1" to the bladder tank
- From the other end of the "T" it is 3/4" to the yard (all under ground - patio and driveway)

Can I take turn the 3/4" to 1" and maintain the appropriate pressure? I can also change the switch on my bladder tank from 30/50 to 40/60...

Wet_Boots

Supreme Member

Posts: 4,071

Location: Metro NYC

4

Tuesday, October 9th 2007, 1:53pm

Consider using Maxipaws. Impact-type heads can endure cruddy water. Valves are less crud-tolerant, unless you spend extra for dirty-water valves.

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