Overlapping zones and sprinkler head precipitation rate

I’ve been noticing that our Rachio wants to water quite a bit more than we would set the manual sprinkler controller, and at the end of a watering cycle there is quite a bit of standing water. I think this is mostly because I haven’t properly set the precip rate for our sprinkler heads, but I also think it’s because I’m not properly taking into the account the extent of the overlap between zones.

In our lawn there are three zones. There is 100% head-to-head overlap, so that the zone 1 sprinklers water right up to the zone 2 heads, and zone 2 provides coverage right up to both the zone 1 and zone 3 sprinklers. All zones are flat, and have the same sun exposure. I’ve ordered catch cups from Amazon, so that I can measure the precip rate, but I’m not sure exactly how to measure and then enter the information once I’ve collected it.

Any one spot on the lawn should be getting water contributions from two zones, so I’m planning on running both zones for say 15 minutes each, then multiply the cumulative water collected by 4 to get the inches per hour precip rate. Even though this is a cumulative collection, it is what I would enter for each individual zone. It would overestimate the actual output of the sprinkler heads, but I think it would correctly account for the fact that all spots are being watered by two zones. Please let me know if this is the correct way to account for this overlap.

The other question I have is on entering the area. From what I’ve read this only affects the water delivered calculation, and not how long or how frequently the zones run, so maybe it doesn’t make a difference. But if I sum the square footage of each individual zone, it will be more than the total area of the lawn. I can easily calculate the correction factor, but I’m wondering if I should enter the actual square footage that each zone covers, or correct it for the overlap.

Finally, given this overlap, is there any reason that would suggest I can’t run flexible daily schedules? I don’t really care about what days the zones run, and the potential water savings from flexible daily appeal to me, I just want to make sure that it’s still appropriate for the above situation, and would work with the above calculations.


I have the same questions! I have 9 zones with 7 of these zones involving some degree of overlapping. I suspect if using the PR rate gathered by only running one zone, the rate would reflect a very low PR rate and thus increase the watering time for each zone - resulting in overwatering due to the other zone’s watering of the same area.

You are asking questions that required me to take The Irrigation Association’s Landscape Irrigation Auditor class, pass the very difficult Certified Landcape Irrigation Auditor test, then pass an actual audit at a commercial property. Answers to your questions are not simple. I encourage you to watch some YouTube videos on irrigation audits. Orbit sells a decent audit kit.

Yes that’s about the only thing you can do to to account for overlap. One other thing you need to calculate is the efficiency of the zones. That will help you account for the fact that some spots don’t have overlap and is an advanced setting for each zone. The below post includes a link to the pdf I used when I ran my catch cup tests and calculated everything I needed

As far as the area goes, I just divided my area between all my zones so that the sum total would be the actual square footage of my lawn. I thought this would be most accurate to calculate the water delivered but I didn’t think about it too much since as you said it doesn’t actually affect run time.

You should still use flex daily, I don’t think this impacts the savings you would get much. The only annoying thing about it is you have to keep an eye on the scheduled runs to ensure the zones that overlap track each other. I think because of rounding error the zones will eventually start diverging in the moisture calculations even if you have the exact same settings for each zone. Eventually they will start running on separate days which is not ideal. Just today I had to adjust my moisture graphs to sync up my overlapping zones again.

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Thanks for the helpful information. I hadn’t intended to go so deeply into things like zone efficiency, but by providing this level of detail, it looks like you’re leaving me no choice. :wink:

I’ve downloaded the PDF. I’m not sure if it’s a cut and paste, or formatting issue, but the link you included somehow got munged in the post. The corrected link is:http://aces.nmsu.edu/pubs/_h/H510.pdf (/pubs/_h/ vs /pubs/h/)

I’ll get started on these recommendations, once again, thanks for the help.

@rustbucket what catch cups did you order? If it’s the orbit, it’ll give you efficiency in their analysis and you can just plug that into advanced settings

Yes, Orbit has the best catch cups and program for homeowners.

Fortunately I ordered the Orbit catch cups, so I should be in a good position to get the efficiency measurement right.

You will like them. I have heard good things from homeowners.