Setup for Overlapping Zones

post by nunny1969 on Jul 18, 2015

I just installed my Iro and working on setting up my zones. I’m trying to understand how Iro accounts for zone overlap and how I should be calculating square footage where zones overlap.

For example, my front yard has 3 zones that overlap each other. Zones 1 and 2 significantly overlap each other (for sake of argument, let’s say they overlap by 50%). As well, zones 2 and 3 overlap each other to the same extent as 1 & 2. (i.e. zone 2 is “filling in the gaps” of zones 1 and 3).

With this scenario, if I enter full square footage for the sprinkler head coverage of all 3 zones, won’t Iro miscalculate the amount of water needed for zone 2 (too much water)?

Thanks in advance for any input.

post by franz on Jul 18, 2015

The zone square footage (advanced settings) is only used for estimated water usage, nothing else.

What the zone really cares about is nozzle in/hr. You can pick which nozzle you think is closest, or do a catch cup test! While not at all necessary, if you do have the closest in/hr for nozzle, it will help the Iro determine the optimal run time.

post by nunny1969 on Jul 21, 2015

Thanks for the clarification Franz. I used the water meter GPM calculation method using custom nozzles, which seemed pretty easy to do. So far all seems good!

post by emil on Jul 21, 2015

@nunny1969, just curious, how long did that setup take for you? Do you have any tips you’d recommend to others after going through the process?

post by jsurpless on Aug 1, 2015

If I have two zones that overlap and have different attributes - for instance, my front yard has two zones that overlap with one being shielded by my house from the sun most of the day, whereas the other is off to the side so it gets lots of sun.

Right now, they water on different days because the shaded zone gets less sun than the other… Should I set them both up as lots of sun because there’s overlap of the shaded zone into the unshaded zone?

post by franz on Aug 2, 2015

There are a few concepts here. In this context the measurements that affect watering duration are the nozzle precip in/hr rate and nozzle efficiency (distribution uniformity). You can use our default nozzles or by using a catch cup test create your own custom nozzle.

Zone square footage only affects the estimated gallons used/saved we display and does not affect the watering duration. Hope this helps.

post by JCE on Aug 21, 2015

I recommend a slightly different approach. I prefer using water meter data rather than catch cups. I believe the meter method is more accurate. Assuming that you have no issue measuring GPM and translating that into inches/Hr, then the only question is what area to use for 3 overlapping zones. Assumption: The three zones all use the same type of heads i.e. same rated flow rates (though ¼, ½ and ¾ heads should be these fractions of a full head). So what you do is measure the total area that all 3 zones cover. Then you count heads in each zone, but use ½ for half circles, and ¼ for quarter circles, etc. Then simply proportion the total 3-zone area to each zone by multiply total area x (#zone1 heads) / (total# heads in all 3 zones). Repeat calculation for each zone. This should work very well for you.

post by intherain on Sep 21, 2015

Thanks! I’ve been asking but no one could answer this for me!

Attached is a rough drawing that shows the overlap.

post by emil on Dec 5, 2015

@JCE, do you know if your zones & sprinkler heads were designed/installed using matched precipitation rate (MPR) principles? In order to be “matched” all sprinkler heads in a given zone must have the same rate of precipitation. Hunter has a great 2 page resource on the basics of MPR.

@intherain, could you detail the zone boundaries in this drawing? As I understand it currently, the # or color represents the number of heads covering each area? I’d recommend giving the Hunter resource referenced above a read and see if it helps to address any of your questions.

Happy to help answer any questions and/or discuss the topic further. This is a great dialog on a common, yet complicated, irrigation system design issue.

post by intherain on May 7, 2016

The 3 zones are vertical there are 4 heads in each zone. All heads have been matched for the precipitation rate for 1/4, 1/2 and full circle.

post by intherain on May 7, 2016

Lets keep it simple and say I have 2 zones and 2 matching heads. Needing head to head coverage. If one zone precipitation rate is 1 inch an hour wont that be 2 inches an hour if I run both zones?

post by bridavis on Aug 6, 2016

This is a very good question - I’m wondering the same thing. Even with all zones set up as MPR, if Zone 1 and Zone 2 overlap, the assumption is that that overlap gets half its water from Zone 1 and half its water from Zone 2 (assuming each zone is using the same MPR). Unfortunately, that gap will only get 1/2 the water it needs if Zone 1 and Zone 2 aren’t watered on the same day, and may never get down to the roots in that case. There’s no way that Rachio knows if two zones overlap, correct?

post by JPedrego on Aug 6, 2016

No there is no way to completely tie them together but if they have the same settings and are on the same schedule they should keep the same schedule. I haven’t noticed a problem with my overlapping zones. (I’m assuming you are on flex daily)

post by Danimalx23 on Sep 26, 2017

Sorry to reply to an old topic here, but I’m trying to figure out the same for overlapping zones. You say zone square footage is only used for water estimation, but what about the formula for PR? Where PR = (96.25(A * B)) / (C) A = # of heads -or- # of emitters B = flow rate (GPM) per head -or- emitter C = zone square footage Using a catch cup test to get an actual PR would be difficult to calculate within the overlapping areas. Best I’ve been able to solve for is by reducing the run time from what Rachio suggests, and adjusting the moisture levels. This is not an ideal solution however.

post by Sprinklerman on Sep 30, 2017

Actually, properly laid out catch cups is the best real world scenario for measuring performance. You should be able to find articles to help do that correctly. There are also several apps now that can help with calculations. You are right about the fine tuning, though. The Rachio app can only calculate from the user's inputs. So, we, the end users, have to pay attention to get the end result we want.

post by Danimalx23 on Sep 30, 2017

How do you set the PR for a zone to account for overlap then? If the PR for zone 1 is .65 Rachio is going to try and run that zone to fill the field capacity. When the overlapping zone starts, it will do the same thing, and I’ll have a swamp in the middle.

post by Sprinklerman on Sep 30, 2017

You’re right. If you had catch cans set around the whole area, the PR around the middle will have the highest amount. That input can be set in a custom nozzle and it should be different from your outside zones. You could also increase the efficiency for that zone. I suggest adjusting the time down for the middle zone to help balance the watering. You may have to experiment with a few times by watching when the water starts to pool, then back off some. When seasons change with temps and wind, the schedule should change too.

post by nvanlaar on Oct 2, 2017

Most manufacturers calculate precipitation rates based on square head to head overlap and head to head triangular patterns. I would use the advertised precip rate of the sprinklers you have and then fine-tune from there. The precip rate is the same whether all three zones run for the same 10 min. or they run 10 min. separately. The same amount of water will be applied.

post by beneb on Jun 12, 2020

I know this is a super old thread, but I have the same issue and I’m still having some trouble understanding. I’m new to Rachio, have a Gen2 controller that I’ve been working on setting up and got confused when trying to do my backyard because I have 4 zones that overlap each other. I should also note, I believe whoever put the system in didn’t do the nozzles correctly because all the heads are the same nozzle in the back (Hunter PGP’s with blue 2.5 nozzles). So, I’m working on correcting that issue, but I’m still somewhat confused by how to input the correct info into my settings to account for the overlap. As I’ve been working through the stuff on Hunter’s site to figure out which nozzles I need, it seems like my middle zones may have different PR’s than the outer zones. Does that matter as long as all the heads in one zone are matched to each other?

This seems like a common situation for home lawns and while this forum post has been really helpful, I was surprised I couldn’t find anything in the web Help Center about this.