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Thursday, August 11th 2011, 10:29pm

Full Pressure on Manual but Low Pressure on Timer - What to do next?


On manual the sprinkler system will run at full pressure but when on the timer it will not fully pressurize any of the zones. We have corrected grounding issues, tried a new timer, ops checked each individual solenoid and they all powered up. The only thing we haven't done is removed the caps and individually clean each of the diaphragms because it seems if that were the problem it would be the same problem on manual and timer. We have had multiple sprinkler people work on it without success. Do you know what else we might try?

Thanks in advance! 8|


Supreme Member

Posts: 493

Location: Seattle


Friday, August 12th 2011, 12:56am

Sounds like the valves just need to be replaced. Are all of them doing this?

What style of valve? Let me guess Toro Jar Top

What do you mean you have corrected your grounding issue?

When you manually turn on a valve- this is a physical mechanical condition. It's like turning on a your hose bib with your hand- you are physically turning it on.

The other end of this is electrical. So if you are able to turn it on physically but not electrically. This usually means it is a electrical issue, or the electrical part of the valve cannot open the valve physically anymore due to a failed valve.

Important information to get:

*Ohm readings to each zone from the controller
*Ohm readings to each solenoid at the valve
* Voltage output to each zone at the controller
*( Not as important) Voltage readings at the valve- inrush current
*Ensuring the flow controls are not turned down

If the ohm and voltage readings are normal and a new solenoid isn't working then a valve replacement is in order.. You can replace the diaphram however I recommend the entire valve.

Central Irrigation

Supreme Member

Posts: 371

Location: Central Minnesota


Friday, August 12th 2011, 7:31am

Sounds like a Rainbird Valve problem. Possibly a Toro Flo Pro valve problem.

A new diaphragm and selonoid takes care of the problem 90% of the time. Hard to tell which is actually the culprit, since when I run into the problem I always replace both. It seems that rainbird selonoids can have a tendency to slowly wear out over the years, and only partially activate. They'll buzz and hum when activated, but still only partially open causing a similar problem to yours. However, a worn diaphragm will cause the same problem. Replace both.

I agree to check voltage at the valve. It's possible you're losing voltage along your zone wire. Make sure the selonoid is connected to the wires when you test the voltage. You want to make sure you're testing under load.


Thursday, August 18th 2011, 10:29am

Ok Manually

8) The reason the valves coming on when you operate it by hand, either via the bleeder plug or by loosening the solenoid is because your allowing the pressure holding the diapahram closed to flow by quickly. Sometimes a valve will not open fully when only the solenoid is loosened, and will also require opening the bleeder. Make sure the center guide rod beneath the valves flow control handle exist, make sure the flow control handle is not fully opened, but just to where turning it down more begins to restrict the flow, then check that all the o-rings, seats and correct solenoid plungers are installed. If a solenoid requires a rubber o-ring, and it's not there, it will allow the solenoid to be tightened down to far, restricting the ability of water to flow through adequately when the solenoids engaged. It could be the wrong solenoid piston(s) were installed, (usually one too long), restricing water flow through solenoid port. You can remove the solenoid and test it at the clock by touching one of the solenoids wires to the common post and the other to the MV Post, then turn the clock on, see if the piston engages fully. You can also remove the solenoid, take a

Sprinkler Marking Flag, or a long narrow rod and see if it will pass through the hole where the solenoid piston seats.
Sometimes a fitting has been installed on the discharge side of a zone valve too tightly, and its threads will partially block the channel where the water/pressure on top of the diaphram is supposed to purge along with the discharge flow. Purchase a new solenoid and test it on one of the valves, if it works, thats the problem, replace them all. Often solenoids are removed without the water being shut off, this allows a rubber o-ring or loose port to blow out without being it's best to work on valves after shutting the water off, and releaving the pressure built-up in the line.....always disassemble components where any parts that fall can be retrieved...

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