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Help with max GPM/heads per zone and other pro advice needed

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Suburbanguy

Starting Member

Posts: 1

Location: Western Mass

1

Sunday, May 19th 2013, 11:17pm

Help with max GPM/heads per zone and other pro advice needed

Was hoping to get some professional advice. I'm attempting to come up with a design for an irrigation system for my house which I plan to install on my own, a little at a time over the summer. I know this is stupid and my priorities are messed up but my ultimate goal is to water everything visible from the street on 1 zone using 15 heads...so I figured there's no better way to know how many I can run than by trying it...so I rigged up 12 homemade bases out of 1/2" PVC. And put 12 cheap home depot pop up sprinkler bases and put on a bunch of assorted MP rotator heads on them and rigged up a crazy octopus of garden hoses and "Y" adapters in my front yard all feeding off 2 regular garden hose bibs on 1/2" copper.....I was suprised it worked fine.....(but that's only 12 and I need at least 15) .....ok now the important part....I have about 40' of 3/4" copper from city main to basement feeding a 5/8" meter which feeds into 1" copper of which after 10' of I will tap in for the system....my static pressure is 87 psi.....with the 12 sprinklers running off several hundred feet of crappy garden hose the pressure drops to 62psi..if I turn on 2 sinks to where I am measuring 1.5GPM from each one the pressure drops to 53psi at the farthest head....if I add up the flow rates for the 12 heads based on the chart on hunters website at the Max flow listed at 55 PSI it equals 11.1Gpm..... is that chart accurate? Can I add the 3gpm I'm getting from the sinks into my design gpm?.....can I add more? also I'm planning on adding fertilizer injection ....so I think I need a reduced pressure backflow preventer.....how will that affect things?also can most controllers operate multiple valves per zone?...in new England am I better off with sch40 PVC piping or polypipe?? Will 1"piping, 1"BFP, and 1" valves be adequate?? ...any advice anyone could provide would be greatly appreciated!

Ocelaris

New Member

Posts: 7

2

Wednesday, May 22nd 2013, 9:37am

That is a ton of questions. But you really need to do some thorough reading on irrigationtutorials.com . Pretty much all your questions are answered on that site. I've been working my way through that piece by piece.

I am in a similar situation as you, 3/4" copper feed from the street, I have 80 PSI static pressure, and it's a bit longer from the street, but the problem is you have 3/4" feed (like me). For velocity's sake, you don't want to go over 11 GPM, realistically with other factors like the house, don't go over 9-10 GPM per zone. The reason to keep the velocity down is damage to pipes. Therefore 3/4" pipe limitation keeps you in the 9-10GPM per zone.

If you've looked at the flow rates for the heads, make sure no zone goes over 9-10GPM, you're going to need 2 zones probably at least. not sure the motivation to make just 1 zone, a second zone is only ~20-30$ more for the valve and piping...

You have to calculate all your pressure loss from start to finish, RPZ lose more pressure than say a PVB. You shouldn't have a problem with pressure, but you'll need to consult the manufacturer's spec's about what the pressure drop is. Again, this is all laid out in irrigationtutorials.

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