Have to cycle valves to get good/consistent pressure (MV setup)

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Kazamali

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Hi folks, found this awesome forum a couple of weeks back. Really great source. I have a really weird problem with my irrigation system and would appreciate any insights (Sorry for the long read). Overview:
-Controller: Hunter Hydrawise Pro HC (24 zone).
-18 zones (12 rotor zones, 6 pop up zones)
-All RainBird valves (~7 years old)
-Master Valve Setup (Rainbird)
-Connection: Main city supply line->PVC ball valve->backflow manifold->Master valve->Zone valves

My issue is that, for certain zones, when I first energize them, the rotors range from just spitting water to gurgling and they hardly rise. If I turn off the zone and IMMEDIATELY reactivate, the heads pop up great, I get full blast service and they stay that way for the duration of the program( this behavior is across all of the rotor zones, except for one). If I leave the system for a few hours and test again, the problem reappears. This happens whether I'm using the controller or actuating the solenoids by hand(for instance, I activate the MV by hand and then walk to the zone and activate it by hand, too). I've replaced the solenoids/diaphragms in both the master valve and the problematic zone plus cleaned out the valve head/body/channels with a wire. I've also replaced all the sprinkler rotors (RB 5000s) in my problematic test zone and still having the issue. I don't have any major leaks anywhere on the property (at least nothing that would manifest itself in a decent amount of time) I'm ready to pull my hair out because for most of the 18 zones, I have to energize them manually for a minute, turn off, then run them for the normal time...rinse/repeat. My lawns have not been in the best shape since we bought this house 5 years ago (2nd owner) so I'm suspecting something pre-existing( as I'm finally taking the time to really look at my irrigation).

My engineering mind is telling me that this is a localized pressure issue that is somehow exacerbated when the system is idle/full of air and needs to 'prime'? Once flushed and primed, everything is great, so it seems my OVERALL city/system pressure is fine. It's like the MV or the zone valve, upon first energizing, either 1. don't get enough pressure or 2. can't open all the way for whatever reason. I've tried messing with the master valve timing and letting it prime the zones for up to 5 minutes before turning on the sprinkler zones, but that hasn't helped neither.

The only things left on my 'to try' list are:

- I have a small leak at the main ball valve joint (on the output side) that I'm going to try and patch, (the leak is enough to fill the box in about an hour) but that's probably a red herring?
- Did I mess up the diaphragm replacements? I'm wondering if I should open them up again and just flush them out with full line pressure?
- Is there something in the backflow manifold that's causing this? I haven't touched this yet.


Any help/advice would be appreciated. I'm pretty handy around the house, but my wife is ready to call the irrigation folks herself with the amount of time I'm spending on this :)

Thank you!
 

Reach4

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I have no knowledge of such systems, but I would watch the water pressure after the backflow manifold to see if the pressure is much difference under each condition.
 

WorthFlorida

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I would first install a bypass of the Master Valve or eliminate it, even if its temporary. Generally a MV is not needed. When installing a bypass, include a tee of the same size pipe diameter of the master valve. At the end of the tee install a ball valve or spigot. With any zone running water should come out of the tee with full pressure and force. If not, it's the back-flow preventer as Reach4 suggest.
Or install a spigot right after the back flow preventer.
 

Kazamali

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This is great advice. Thank you very much for taking the time. It may take me a while to do all that since I'll have to do some digging, but you did give me a good idea: I think I can take an old diaphragm, cut out the center and put it in the MV, thereby, "bypassing" it, right? Then I can do the first test that way....if THAT doesn't reveal anything, then yeah, I'll go with the 'tee' method to test the backflow.

Btw, I thought the whole purpose of the MV was to avoid having the entire system pressurized 24x7? Sounds like a good idea to me.

Thanks!
 

WorthFlorida

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Of the 12 rotor zones, how many rotors in each zone? It's strange that one zone always seems to work. There is a possibility that during installation by the previous owner a small stone or other debris is jammed up at an elbow. But not knowing the pipe layout it would be hard to tell where it might be. One way to test an individual zone is remove the first sprinkler from the zone valve. Water usually will shoot out like a geyser without any restriction. I came across this article about master valves.

 

Kazamali

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Most rotor zones are running 4 heads (two zones running with 6 heads), all @3GPM. I think I may have found something (call it a mitigation because I don't have a clear root cause yet:
-I'm dropping all the GPMs down to 2. That seems to have helped a bit.
-As stated earlier all rotor zones are having the problem except for one, and I think I know why: That zone's valve is 'below' all of its heads. The other zones have at least 2 heads that are on a slightly lower elevation. I didn't notice this because Austin has VERY porous ground and I never had any puddling issues. I ordered a bunch of check valves and going to try that.

I'm hoping with those two changes, I've finally mitigated the issue. Not sure why it's showing up now (or mebbe I'm just finally noticing it?). My static pressure is 55PSI which, according to my local water company, is on the higher end of the acceptable range.

I'll keep y'all updated when I have everything put in, and thanks for all the input here.

And @WorthFlorida , I've permanently left my MV on (to the point in your article above) thank you!
 

WorthFlorida

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3 GPM per rotor is a lot of water to get from a city supply. Most meters are 3/4" with 3/4" pipe to the home and though at a constant 60PSI in theory is 23 gallons per minute but it'd be rare that the city pressure can hold at 60 PSI with water flowing. Plus all the restrictions through a back flow preventer, elbows, valves plus pressure is lost to power the rotors, going to 2 GPM or even smaller is always better. Low watering for longer periods is preferred and for environmental concerns.

While the irrigation system is on, you still need enough pressure and flow to supply the house needs. There was a post here a few years ago that when the irrigation system turned on, it was sucking in air from a shower head inside the home if someone was using it.

Elevation between the valves and heads will have little or no effect unless it's 20'-30' difference. Not sure what the check valves will do for you. No reason that I can think of? What you really need to do is put a pressure gauge on after the back flow preventer and get reading with each zone running. With a tattletale gauge on a spigot on the house side, look at those readings. You're about right 4-6 rotors per zone but not more than 6 rotors on city water. That will be about 12 gallons GPM @ 60 PSI but you'll need to find what the city water can supply. Some just use a hose and time it filling a 5 gallon bucket.
 

jadnashua

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Is it possible that the low-voltage power supply is marginal, and on the zones with more devices, it can't power them all open properly?
 

Kazamali

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Hi folks, thanks for all the advice here. I think I finally solved it with two things (but I think more because of the latter): 1. reduced rotors from 3gpm nozzles to 2gpm AND putting in adjustable Hunter check valves under the lowest elevation heads.

Perhaps I have some weird fluid dynamics going ono_O, but my only thought is my particular design/pressure makes it extremely difficult for the zone to equalize all of the empty pipes AND force all the heads up. I feel like without that initial sitting water to assist (just air, which compresses quite a bit) there wasn't enough oomph to lift (and seal) the heads...it was almost a vicious cycle of playing pressure "catch up" and never quite getting there unless I shut the system off for a few seconds and then let it "try" again with full pipes. Again, this is ONLY with the zones on a slight elevation(my property is relatively flat actually)...two other zones that are VERY level, have never had an issue.

I've literally checked everything in the system and my static house pressure is 45gpm (which is normal, per my water company) and then drops to 25gpm when irrigating. My development area is about 7 years old, so I'm wondering if the pressure has dropped over time....? These sections of my lawn have ALWAYS been in bad shape since I bought the house 5 years ago, so I'm assuming it's pre-existing, but I'm just finally paying attention now? Anyway, perhaps I just covered up a larger problem, but my grass is already looking better and my water bill is manageable again.
 
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