Can/should I rewire my 3 zones to a single zone?

Hi - I have three 500 sq ft grass zones in my back yard. The three zones are being irrigated with Hunter MP800 rotator nozzles, which have a lower output rate of approx. 0.7 in/hour.

When overseeding for rye this year, my yard dude (who seems very knowledgeable) mentioned that there could be too much water pressure for the zones (each zone has 5-6 rotors) which could cause the rotors to malfunction.

He recommended that I rewire all 3 zones to a single zone on the Rachio. When he manually turned on the 3 valves simultaneously, he said that the spray coverage was identical.

My question is this: Is it OK for me to rewire my 3 zones to a single zone? I would be concerned about pressure/stress to the system when all three zones turn on/off simultaneously.


I also have MP Rotators. I think the fewest I have on one zone at the moment is 4. I do not think I have run into any issues. However, it seems like I have heard that too much pressure can cause the nozzles to wear out faster. I have the PRS bodies, which is pressure-regulated, and may take care of any issue. I probably would suggest measuring the pressure and going to a Hunter sprinkler supply store (not a big box store or the like). I will try to remember to do the same in spring or ask with their knowledge about the bodies too.

I would be more concerned about over-current on the system. If the Rachio senses too high of current, it thinks it is a short or the power cannot handle it, so it turns off the zone. I do not remember if the maximum is 2 or 3 including any pump or master valve you might have. Do you have either of those?

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Actually the MP800 are .8 in/hr.
Hunter PRS40 Max PSI is 100 PSI

Thus, any PSI higher will damage the internal pressure regulation and potentially distort the nozzles effective DU and longevity. After all they are Hydraulic and thus the parameters engineering has suggested for maximum effectiveness since their invention by Walla Walla.
They have always recommended 40PSI, and you will see Hunters Data Max PSI @55.
Performance Data Sheet - MP Rotator MP800 Performance Data MP800SR | Hunter Industries

MP Rotator Brochure- Check the T" for testing Dynamic Pressure at the Head if you have questions regarding non-regulating heads and dynamic pressure.

Thus a regulator at the Irrigation sub-main to reduce high pressure and pressure regulation at the head Rainbird or Hunter whatever you have can be retrofitted or use In Flow regulation and PM me on where to order the the stems which will regulate the head pressure and flow from over 150 PSI to less than 40PSI to be in specification recommendations and performance.

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@AzJazz, the implied questions are:

  1. What bodies do you have? As @ProWater mentioned, the operating range of the PRS40 is 15-100 psi (although 15 would have other issues on my zones).
  2. What is your pressure of your system (before any regulator)?
  3. Do you have any other regulator (I do only on my drip line)?

I did that about 5 years ago shortly after I installed MP nozzles in all my sprinklers. I didn’t do it so much for the pressure issue (although that is a concern), but I did it for the time. I went from 14 grass zones to 6, and went from watering up to 14+ hours to 6+ if all zones happen to run in the same day (Flex Daily). Today, I still have my zones wired together. I had every intention of replumbing the zones, but the wiring has been working fine, so I’ve moved on to other projects.

If the zones are similar profiles (soil, sun/shade, slope), then I say go for it. If you don’t have a master valve like me, you can wire 3 zones together. If you have a MV, you are capped at 2 zones being combined.

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The problem you will have is this, each section of your yard will probably have different water requirements. If on area has full sun it will have a different transevaporation rate that of an area with partial sun or complete shade. It will also depend on the plants you are watering.
Usually a professionally designed system will take all of this into account.
There is probably a reason it was designed as 3 zones.
Simply wiring everything together is most probably a bad idea if your system was designed correctly in the first place.

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I agree with @tmcgahey & @trivialnonsensical that several factors should be taken into account (especially if it is absolutely not needed) before combining, such as soil, sun/shade, slope, crop, etc. Since all three zones are grass in your backyard, it seems likely that at least some of those are the same, but not necessarily all. I know my backyard is the same crop & soil, but the sun/shade & slope are different in a couple of zones.

I have an 8 zone rachio for backup in case my 16 zone controller has a problem. When my 16 zone crapped out on me I had to use the 8 zone controller until I could replace my 16 zone controller. I have 9 valves but only 8 zones on the backup controller. I wired 2 drip valves onto a single zone. It ran that way for more than a year with no issues. Considering the small number of heads you have I wouldnt worry about it. Nozzles are cheap and easy to replace. Most cities don’t supply more than 60 psi anyway so its unlikely you will damage.the rotors.

Hi, guys, thanks for all the great feedback and suggestions!

My yard guy said that too much pressure can cause some of the rotators to freeze in position, which I do have occurring.

I decided to pick up a Hunter MP Rotator pressure gauge (A Hunter MPGAUGE like this one) to see if there was an actual pressure issue.

I got the meter today. The needle rests at 10 PSI instead of resting at zero, so there is likely to be an offset in my readings. That said, the meter read 56 PSI on my section that had the fewest MP rotators, so I am pretty sure that I don’t have a real pressure issue.

Based on your suggestions, I will not make any modifications to the wiring at this time.

Is there a way to get the needle reset on my meter? I don’t see any adjustments.

I have seen my rotators freeze in position more from low pressure, usually caused by dirty filter by the main valve. Occasionally, I push down of the nozzle so it does its cleaning and it helps.

This posts replies have a lot of great input! :100: