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capmaint
01-18-2005, 04:57 PM
For starters, Im not a sprinkler guy. I know just enough to get in over my head though....I put a 6 zone system in for my dad recently and the pressure at each head is less than what I anticipated. I cut into a 3/4" supply line, then ran 1" PVC for about 30 feet (thinking the larger diameter would give me more flow, therefore more pressure) and then used 1" valves. I came out of the valves however with 3/4" PVC and the entire system is comprised of 3/4" PVC with 6 to 8 heads on each valve.

If I get rid of the 1" PVC and change the vales to 3/4" valves so that everything is consistent, should my pressure at the head improve or will I not see any difference?

Thanks for any help.....

Planter
01-18-2005, 06:24 PM
If I get rid of the 1" PVC and change the vales to 3/4" valves so that everything is consistent, should my pressure at the head improve or will I not see any difference?


It's a bit more complicated than that. Going back to 3/4" will cause more friction loss and therefore less pressure at each head. The lines to each head are sized according the the needed volume for the heads downstream. If you need 12 gallons per minute downstream you will use a 1" line for 9 gallons per minute you can use 3/4".

What is the pressure at the line you cut into? What kind of pipe is it? Did you flow check it to see how much you have to work with?

What heads did you install?

Likely you have a pressure/flow problem with the 3/4" supply line you cut into. You may have to add more zones to get the pressure/supply you need.

Best of luck!

capmaint
01-18-2005, 06:44 PM
Planter, thanks for the response. I cut into a copper supply line that had 65 psi. I dont know what the flow is however, and I used Hunter 0-360 adjustable pop up heads. From what you said, Im guessing im better of leaving well enough alone for now...?

DanaMac
01-18-2005, 07:24 PM
I know most of you will disagree, but it can be done. In our area most homes are 3/4" copper. That is the size of the supply line to the home and throughout. So it is of course what we cut into. When I was still doing installs, we designed zones between 10-15 gpm. Pressure was usually 50-60 psi. And pressure for the zones were fine. We upsized to 1" at the valve and all lateral pipes we 1" as well. 99% of the time the zones had great pressure. 6-8 heads SHOULD be ok if nozzled properly.

So... a few things to check. If you have a mainline that is extremely long, or if your laterals (zone pipes) are extremely long, that could cause the flow/pressure problem at the heads. You said you used Hunter 0-360 adjustable pop up heads. Are those rotors (Hunter PGP) or fixed spray heads that don't move back and forth? If they are PGPs, reduce the nozzle sizes. Instead of a head that will put out 3-5 gpm, you can reduce the output to help your pressure prob. You also need to match the precip rates if possible. Let's say you have 6 heads in a rectangle - 4 corners and 2 half circles. If all the heads are nozzled the same, the corners will get twice as much water than the area that the half circles cover. Does that make sense? I could explain things in more complicated terms and give precip rates and formulas and all that crap, but basically heads in the corners need to put out half as much as heads covering half circles. And half circles need to put out half as much as full circles.

More details and we can help more.

capmaint
01-18-2005, 09:51 PM
The heads are the fixed spray kind. I will try adjusting the corners down and see what happens. So, would I be wasting my time to change out the 30' section of 1" pipe and valves and replace with 3/4"?

mrwettech
01-18-2005, 10:25 PM
It may be as simple as the gate valve to the house is not opened all the way. I'm assuming that is where you shut it off to make your tee connection. The reason I say this is because it does not sound like a pressure but, a flow problem. I have seen it many times. First step in trouble shooting this problem is check for flow restrictions starting at the house valve. Make sure it is "fully" open. That should be your first step. If that is not the problem then you can discuss the next step. I hope that helps.

DanaMac
01-18-2005, 10:56 PM
Very true. I have gone to jobs as well, and the shut off handle is half closed. I have also found handles on either side of the water meter, and on backflow preventers that were also partially closed. yes it does sound like a flow problem, not pressure. You can have 100 psi with only 2 gallons a minute of flow if things are screwed up bad enough. I've also seen the curb stop valve (stop and waste or whatever they are called in your neck of the woods) partially closed.

What pattern do you have the nozzles adjusted at for each zone? Example - 6 heads at full circles could be close to 24 gpm with 15' Rainbird full circles. But 6 heads that are all corners at 15' would be closer to 6 gpm. the different companies have different rates of output for their nozzles. At 30 psi at the heads 15' half circle nozzles - RB puts out 1.85 gpm, Toro 1.65, Hunter adjustable 1.75. It may not seem like much, but when you add up the differences over 6-8 heads there could be 2-3 gallons difference between nozzles.

jerryrwm
01-19-2005, 01:38 AM
The heads are the fixed spray kind. I will try adjusting the corners down and see what happens. So, would I be wasting my time to change out the 30' section of 1" pipe and valves and replace with 3/4"?


DO NOT change out 1" pipe. If anything, you would change the rest of the 3/4" pipe from there to the valves and from the valves out to a few heads on each zone. You are having a serious loss of pressure because your lateral lines downstream of the valves is too small. So if anything you would increase the size of the pipe.

Now - what size nozzles are you using on each zone? 17' - 15' - or 12'? And how many are Full circle, Half circle, Quarter circle? How far apart are they spaced? If the heads are spaced at 15' or less, try using 12' nozzles. It ain't right but the 12'ers will throw further and more consistantly than the 15'ers at low pressure.

Let us know,

Jerry R

jerryrwm
01-19-2005, 01:43 AM
The heads are the fixed spray kind. I will try adjusting the corners down and see what happens. So, would I be wasting my time to change out the 30' section of 1" pipe and valves and replace with 3/4"?


DO NOT change out 1" pipe. If anything, you would change the rest of the 3/4" pipe from there to the valves and from the valves out to a few heads on each zone. You are having a serious loss of pressure because your lateral lines downstream of the valves is too small. So if anything you would increase the size of the pipe.

Now - what size nozzles are you using on each zone? 17' - 15' - or 12'? And how many are Full circle, Half circle, Quarter circle? How far apart are they spaced? If the heads are spaced at 15' or less, try using 12' nozzles. It ain't right but the 12'ers will throw further and more consistantly than the 15'ers at low pressure.

One other thing. When you cut into the 3/4" copper, I'm assuming you used a compression tee to tap off of it. How big a piece of copper did you cut out of the line and is the discharge part of the compression tee centered over the gap in the copper pipe. The part you cut out should be at least 1" and even 11/2" is okay. But if you cut out just a small bit, you are severely restricitng flow and losing pressure right there.

Let us know,

Jerry R

capmaint
01-19-2005, 09:09 AM
Thanks for all the help. I put the system in about 7 months ago and I dont remember all the specs. There are 12' and 17' heads out there and it seems I tried to keep everything about 10 to 12' apart....I will take all the suggestions that have been given, do some troubleshooting, and see what happens. It may be that we just end up with a crappy sysytem and I stick to things I actually know......Thanks again!

SprinklerGuy
01-19-2005, 12:06 PM
bet the valve isn't open all way...either at meter or house....somewhere before the irrigation valves.....very common.

Check flow controls on irrigation valves also...sometimes they aren't open all the way...or you could call me at office and i can send a tech out.......