I have a 6 zone system and recently when the system runs it looses pressure when switching zones. If I turn the system off then back onto the zone it runs fine, even runs fine when I switch zones manually. Running 1 1/2 hp pump without a pressure tank and haven’t had any changes to the sprinkler heads. A leak in the system doesn’t make sense since I can run them all fine manually. Could there be an issue with the control valves having a longer delay, increasing the pressure and when it opens to the new zone creating a venture effect and causing the pump to loose prime?
Pressure loss when switching zones
- Thread starter Pete1973
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WorthFlorida
Clinical Trail 5th session completed 4/24/24.
When the zones change is the previous zone completely off and only one zone is dumping water or two zones are open dumping water?
From your description I’m suspecting two or more zones are open at the same time. You’ll need a volt meter and set it to the scale that can read 24 volts AC, any cheap one will do. At the controller with one zone operating place one lead of the voltmeter to the “common” and the other lead on the wire of the active zone. Probably start at zone 1. You should read approximately 24v ac. At zone 2 and the other four you should read zero volts.
Wait for the timer to switch zones and during this low pressure condition read the voltage at zone 1 and zone 2. We want to read 0 volts at zone 1 & 24v at zone 2. All the others should read 0 volts.
If there is voltage on the zones that should have zero volts the problem lies in the controller. If all the zones are connected with plug in modules that can be removed one of them may be bad. Some timers have all six built in and others the first three or four are built in and modules are added for additional zones. You can remove each zone wire at the controller and check voltages to prove it’s not any short or bad valve beyond the modules. If you have plug in modules remove one of them and test against if a module is the cause.
What is the model of your timer/controller?
The valves themselves are open or closed only, nothing in between. With 1 1/2 hp pump it should easily handle two zones before noticing a big drop in pressure.
From your description I’m suspecting two or more zones are open at the same time. You’ll need a volt meter and set it to the scale that can read 24 volts AC, any cheap one will do. At the controller with one zone operating place one lead of the voltmeter to the “common” and the other lead on the wire of the active zone. Probably start at zone 1. You should read approximately 24v ac. At zone 2 and the other four you should read zero volts.
Wait for the timer to switch zones and during this low pressure condition read the voltage at zone 1 and zone 2. We want to read 0 volts at zone 1 & 24v at zone 2. All the others should read 0 volts.
If there is voltage on the zones that should have zero volts the problem lies in the controller. If all the zones are connected with plug in modules that can be removed one of them may be bad. Some timers have all six built in and others the first three or four are built in and modules are added for additional zones. You can remove each zone wire at the controller and check voltages to prove it’s not any short or bad valve beyond the modules. If you have plug in modules remove one of them and test against if a module is the cause.
What is the model of your timer/controller?
The valves themselves are open or closed only, nothing in between. With 1 1/2 hp pump it should easily handle two zones before noticing a big drop in pressure.
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Only one zone is getting water at a time. Unfortunately this is a system that was in place when we bought the house and it doesn’t have a pressure guage or a fitting in the pump or plumbing to put one but by the tone of the pump the first zone valve is definitely closed for 2-3 seconds before the next opens. It’s a rain bird digital control and the voltage is correct with 24 volts only on the zone that’s selected. Bit after doing a bit of better looking today I found the following
There was a small leak on the suction side where the threaded PCV fitting goes into the pump. After wiping a lot of pipe dope away I found the location so for a quick fix I had some 2 part pool repair epoxy that I mixed up and sealed it. I ran the pump for 45 min on one zone to keep the pressure off the intake side as the only time I noticed the leak was when the pump was off. It’s 95% sealed now, and seems to function normally by a quick test. I’m going to watch it over the next week or so and if this resolves or improves the issue I may just cut all the old plumbing out an fix it properly to include a pressure guage this time
There was a small leak on the suction side where the threaded PCV fitting goes into the pump. After wiping a lot of pipe dope away I found the location so for a quick fix I had some 2 part pool repair epoxy that I mixed up and sealed it. I ran the pump for 45 min on one zone to keep the pressure off the intake side as the only time I noticed the leak was when the pump was off. It’s 95% sealed now, and seems to function normally by a quick test. I’m going to watch it over the next week or so and if this resolves or improves the issue I may just cut all the old plumbing out an fix it properly to include a pressure guage this time
I have seen this on a lot of systems, especialy ones that are near their max capacity. When zones are laid out to their max alot of times they can not keep up when the zone switches.
Why? There inst enough available water to actually seal the heads, what ends up happening is they never fully pop up and leak from around there seals. Once a pump's pressure drops to low, they sometimes have a hard time recovering, mainly due to cavitation. The pump is spinning faster than the water coming through it and it begins to create air bubbles. Air pockets in water does not help.
So what do you do? Some controllers have a programmable "start delay" or a "station delay". you can set this to make sure your pump builds pressure and shuts off between zones.
If there is no station delay, you can set the last zone on a different program and have it run by itself
Next would be put in heads that have lower spring resistance. Hunter I20 springs are really tight, but Rainbird's 5000 series are a lot looser and will usually work
rich@sprinklerresource.com
Why? There inst enough available water to actually seal the heads, what ends up happening is they never fully pop up and leak from around there seals. Once a pump's pressure drops to low, they sometimes have a hard time recovering, mainly due to cavitation. The pump is spinning faster than the water coming through it and it begins to create air bubbles. Air pockets in water does not help.
So what do you do? Some controllers have a programmable "start delay" or a "station delay". you can set this to make sure your pump builds pressure and shuts off between zones.
If there is no station delay, you can set the last zone on a different program and have it run by itself
Next would be put in heads that have lower spring resistance. Hunter I20 springs are really tight, but Rainbird's 5000 series are a lot looser and will usually work
rich@sprinklerresource.com
