Not Enough Pressure for Sprinklers

I'm at my wit's end with my sprinkler system. Here's an outline of the problem:
Sprinkler heads don't have enough pressure to spray water far enough to cover lawn If I loosen the solenoid on the valve assembly to the point where it starts to leak, the pressure increases dramatically I've replaced the valve assembly. First test worked perfectly. Three days later, the sprinklers barely come on at all unless I again loosen the solenoid
I'm at the end of my rope with this. Can anyone suggest what could be wrong?
Thanks.
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Fleemo wrote:

The valves I've seen are "pilot-operated". The solenoid merely opens/closes a tiny port which admits water pressure to a large diaphragm which in turn does the actual valve opening.
Very small amounts of dirt/sediment in the water can cause clogging of the tiny pilot orifices.
Start by determining the mfr and look up their web site for specific advice or even call them.
Jim
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Thanks Jim, but I've already contacted the manufacturer (Orbit). They've been very kind so far, and sent me a brand new replacement valve. As I mentioned, I replaced the valve, it worked perfectly first time I tested it, and three days later barely works at all unless I loosen the solenoid. Once the solenoid is loosened, it works fine, plenty of pressure. I don't know where to go from here. :{
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snipped-for-privacy@comcast.net (Fleemo) wrote in

Sounds like you may need to add a filter before the valve. Are you using well water?
Brad
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Hey Brad,
No, I'm using municipal water.
I could see how minerals and/or sediment could eventually build up and clog the valve. But a brand new valve? There's gotta be another reason.
I don't quite understand the concept of why so much more pressure is available if the solenoid is loosened. Obviously there's enough pressure in the line for the sprinklers, it's just not getting to them unless the solenoid is loosened. :/
I'm wondering if I'd have better luck replacing the Orbit valve with another brand, say Toro or Rainbird?
-F
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Pull off the solenoid and look closely. A single bit of grit can cause it to stick.
I have 8 orbit valves. One of them always sticks after spring thaw. Simply unscrewing and rescrewing the solenoid and putting it back together fixes it.
Check to see that the wiring or tubing isn't putting any torque on it too.
A filter is always a good idea.

--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
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I had a similar problem, I was sure it was the solenoid, after replacing like you did problem was still intermittent. It turned out to be a cracked riser beneath one of the heads,probably got stepped on. The only way I found it was I went to install a swing arm (to lower it) and discovered the problem.

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I appreciate the input, but I just can't belive it's "gucked up" in three days when it took months (if not years) for any symptoms to appear initially.

After replacing every part of the valve assembly and even the entire valve itself, I would lean toward this diagnosis. The trouble is, how can you track it down? Is there a way you can test the pressure of each sprinkler head or riser? Perhaps cap all the other sprinklers and test the pressure one by one?
-F
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Fleemo wrote:

You can usually see water running out around the riser, or someplace besides the spray nozzle. On the outside chance there is dirt in the system, take off a couple of nozzles and run water to flush it real well. I helped hubby rehab the sprinkler system for our condo, which was badly neglected for a long time. He would change out a sprinkler head or fix a pipe but not try to keep dirt from falling into the open connection. I used to get a jug of water to rinse dirt off the connection before he opened it up :o) We also found that whoever maintained the system before had discarded the little filters that come with the sprinkler heads; don't know how much difference they make, but most water supplies will carry some sand/debris at some point. Solenoids are the remaining mystery, to me - gotta be a guy to understand them :o)
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Did you drop any dirt in the pipe while you were replacing the valve?
You _always_ see most guck in valves after disturbing the plumbing upstream. That's why whenever you replace something, you should flush the system for a few moments before doing your final reconnects.
My clothes washer filters always gunked up within a few days of doing anything to the well pump...

Leaks in irrigation system lines often show up as fine water jets going off in one direction or another. These jets will "drill" holes in the dirt. Either you get a hole appear in the ground with a fine mist coming out, or, the dirt collapses into a "mini sink hole".
Some sprinkler units have the ability to be shut off (eg: the tiny screws in the top of many pop-up mist-ers). Sometimes you can clamp all those down and see if the hose will retain pressure. But, the pop up heads generally leak anyway, so, true pressure testing requires you to dismantle the circuit section by section.
I do not believe that a leak is your problem. The valve is sticking. A leak wouldn't do that. Fine grit is the likely cause.
--
Chris Lewis, Una confibula non set est
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No, I was very careful and didn't get any dirt in the system, nor did I do any work upstream of the valve. The valve was it. And I did let it gush a fountain of water a moment before putting it all back together. Again, it worked great immediately after installing the new valve, now it's worse than ever.
So let's examine the facts. The system works perfectly when the solenoid is loosened. What does that tell us? Wouldn't a break in a riser result in a loss of pressure to the sprinkler heads regardless of whether the solenoid was loosened? What is happening when the solenoid is loosened? Is it allowing water to bypass the solenoid, permitting full pressure, which might indicate a clogged solenoid?
The loosening of the solenoid is telling us something, I'm just not experienced enough to know what that is.
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A break in the riser (supply side of valve) would have to be _very_ substantial to affect to affect the valve, and I'd expect you'd to have a gusher in the dirt somewhere. Because it'd be leaking as long as the shutoff valves were turned on. Continuous leak.
On the other hand, I've seen situations where if the output side of the valve is "too open" for the flow rate of the supply, the valve will oscillate on/off. [We use Orbit valves.] Indicating that the valve may behave wierd if it's trying to supply too much and can't retain enough pressure to keep the valve open.
But, this isn't continuous "low flow" thru the valve, it's very loud banging, pipe shake, etc. Like severe water hammer. Which is, after all, exactly what it is.

As I mentioned before, I've had these things stick after overwintering, but it clears up once it's operated once or twice.
It _could_ be you're seeing a different variant of the "not enough pressure to keep the valve full open", and instead of banging, you get low flow. By backing off the valve, you're decreasing the spring pressure.
What's the supply pressure? Well or municipal? Are the shutoff valves "full aperture" (eg: gate or ball) or washer-type stop valves? Supply pipe size/length? Flow rates on associated heads?
--
Chris Lewis, Una confibula non set est
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Thank you for all the input on this sitution. I finally just dove in and started digging up sprinklers. I found broken elbow connectors on four out of seven sprinkler assemblies. These elbows were intended to be a breaking point, breaking instead of the pvc pipe breaking. Much easier to repair. But I believe this batch of elbows were defective. Far too many were broken, and upon buying replacements, I found that they've been completely redesigned, eliminating the spot where they all seemed to have broken.
I believe my problem was a combination of a faulty valve assembly and these cheesy elbows. Seems to be working pretty well now, with one caveat which I'll post seperately.
Again, thanks for all the input here.
-Fleemo
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seems pretty clear its getting gucked up... get a filter.
randy
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