SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Hi all - Long time reader, first time poster. I've been using some suggestions to troubleshoot my system and now Im looking for some more suggestions from you experts. So here's the deal, bought a house last year that had a system installed. Was told that it was a self draining system and from moving a couple of heads I can see there's a tee under each head with one end going to the head, the other going to a self draining valve. The zones are all run with 3/4 inch black irrigation pipe and all of the zones terminate back next to the house in a single valve box that has the valves for all 5 zones. In the house I have a copper manifold that takes a 1 inch feed and breaks it out into multiple 3/4 inch feeds. The sprinkler system attaches here and then converts to 3/4 inch PEX all the way to the side wall where it then turns back into 3/4 inch copper. From there, it goes into the back flow preventer, on the other side of the back flow it is 3/4 inch PVC down to a manifold they built out of 3/4 inch PVC which has all the valves attached.

So.... My problem is low pressure. My biggest zone only has 4 heads and I cant seem to get decent flow out of the zone. The sun finally got hot here in MN and its obvious from the areas of brown grass that the heads are covering close to the head, then at the end of the stream. The middle section just isnt getting enough coverage and the grass is starting to get brown. The heads are all rainbird 5000's and I've tried every adjustment possible. I even changed the nozzlesfrom 2 GPM nozzles to 1.5 to see if I could get better pressure, that didnt seem to help. The bucket test I did seemed to give me about 6 - 6.5 GPM. I have a blow out valve next to the driveway that's always on so I did the test from here since I figured it would be very close to what a zone would see.

The thing that drives me crazy here is my neighbors on either side of me having systems that look like they're on a golf course. Tons of pressure and great coverage and 6 heads per zone. I bought a rainbird pressure gauge and tested my system. I appear to have around 42 PSI. I tried it on my neighbors and he has the same pressure. The only difference between our systems is that he has 1 inch all the way from his main, through his backflow preventer and then at the valve for the zone his change to 3/4 for the zone.

So heres my question. My conversion from 1 inch to 3/4 inch happens at my manifold by the main, his occurs right at his zone valve. Could that make a big difference? Ive read that having 1 inch through a back flow preventer can make a difference. I wouldnt mind running 1 inch to the backflow preventer in the house if I knew it would make a difference. But Im wondering since we have the same pressure if that could really be it. Seems like it could be but Im not sure. I also did a test tonight where I left the pressure gauge connected to the blow out, and the turned on a zone. The pressure dropped as the lines filled, and then once we had water pressure it came back up to about 22. That seems low. Would a bigger pipe help with the pressure?

Any input anyone has would be appreciated!

Thanks for the input. I've already checked all the valves and it appears that they're fully open.

I should clarify, both the neighbor and I have a 1 inch main line coming in. I think the difference is his goes to a 1 inch manifold and mine goes to a 3/4 inch manifold (on the output side of the manifold). So I have 3/4 inch PEX running to the back flow from the manifold and he has 1 inch.

Im willing to try running 1 inch from my main to the back flow preventer to match what he has, but Im wondering if that will really make that big of a difference. I have 3/4 inch PVC coming off the backflow output down to all 5 valves where as he has 1 inch coming off the backflow to the valves.

I guess my question is, would moving the 1 inch closer to the valves make a significant difference? Since the neighbor has 3/4 inch irrigation in his zones it seems to me that its really just a matter of where we transition from 1 inch to 3/4 inch piping. His is close to the zones and mine is right off my main.

I think the next step for me is to cap all the heads in the zone and see if I see the water meter moving. If I do, I'll likely just take the drains out and see if that helps.

Thanks for all your tips!

All of the valves are ball valves as far as I can tell. The pipe layout looks like this. Im putting the pipe size in quotes between the items.

Mainline (1 inch) Manifold (3/4 inch pex) back flow preventer (3/4 inch PVC) PVC manifold to split to zones (3/4 inch PVC) valves (3/4 inch irrigation pipe) sprinkler head.

So most of the system is 3/4 inch. Essentially, I only have 1 inch coming in and to the manifold with the water meter in between. A neighbor was telling me that the inside diameter of PVC and PEX can be much smaller than copper. Is possibly an issue?

I've only done the pressure test for far and that I did with a RainBird pressure gauge. I also did the bucket test for GPM which came out to around 6.5.

I've opened the bleeder valves and I get the same pressure as I do when I open the valves electronically. I double checked all the valves last night and they're all open all the way.

I can take all the heads off a zone and plug them to see if the auto drain valves are leaking badly but it seems odd that all zones would have that issue. The only thing I can think of is the 3/4 inch pipe

Hi Wet_boots - Thanks for replying and sorry for not answering your questions.

The valves are RainBird DV-100s (1 inch in and out). The manifold that the installer built out of PVC (made out of 3/4 inch PVC) has 1 inch male screw ends that go onto the valves. From the looks of it, the 3/4 inch black flexible irrigation pipe comes off the other end off of 1 inch adapters screwed into the back side of the valves.

The back flow preventer is a Watts 800M4 1 inch.

So the 3/4 inch copper comes out of the house, goes to a 1 inch adapter into the back flow, then 1 inch coming out of the back flow to 3/4 inch PVC which the entire PVC manifold is built out of but then converts back to 1 inch to go into the valves.

The run from the main in the house to the copper manifold is less than 3 feet

From the manifold I have 3/4 inch PEX to the outer wall and that run is 25 feet.

From the outer wall it transitions to copper to go outside and that run to the back flow preventer is only 2 feet.

My lot is only a half acre and the sprinklers are only on about half of it so from the zone valves (which are all right off the PVC manifold) to each zone have to be pretty minimal.

As far as the flow and pressure testing you are referring to. You're suggesting I measure how much water passes through the meter while running water in the house? Should I just open a couple of the sinks around the house and see how much water passes during a minute?