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 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 show 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) principals? 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 inch 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 setup 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 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 bridavis on Aug 6, 2016

Good point, same setting should keep them on the same day, I’ll have to take a closer look at the settings for adjacent zones.

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 users 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.

Rachio has created a paradigm shift in how residential irrigation water users think about watering their lawn. It has helped the end users become more intimate with their controller settings and how they effect their green spaces.

post by nvanlaar on Oct 2, 2017

Most manufacturers calculate precipitation rates based on square head to head overlap (which is what you appear to have) 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. See here for a good explanation.

For water use/square ft. calculations I would simply divide the area into thirds. Each zone effectively waters a third of the area.

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. Here’s a very simplified pictorial representation (I have head to head coverage, but that can get confusing to look at so I just drew the symbol of the arc pattern)

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 is what I think my process should be moving forward (but looking for feedback here):

1. Get new nozzles to match PRs of all heads in each zone
2. Use theoretical values from Hunter’s specs to guesstimate total PR for the area in each zone
3. Use catch cups to verify theoretical PR and adjust as needed.
4. Input that value into Nozzle PR on advanced settings for each zone (or come up with a multiplier to compensate for the overlap between zones?)
5. Adjust time values for overlapping zones or is efficiency a better option (essentially double the default for areas of overlap)? Does flex daily schedule adjust zone times based on weather? My fear is any adjustments I made might get lost if it adjusted to compensate for some extra hot or cool days.

Sorry if this is re-asking some of the same questions, but my brain is having trouble with this for some reason and I want to get it right.

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.

post by Sprinklerman on Jun 20, 2020

Most installers use the same nozzle in all rotors because it’s easy and they don’t have to think.

1. Yes.
2. Hunter specs are done in a non-windy building. But you can work from those specs.
3. Yes. And you’ll learn a lot about coverage from the rotor to the end of the throw.
4. Just input values and use advance settings to find optimum watering time.
5. Flex will adjust. It may also not even water the middle zones on the same day as the outer zones since the precipitation rate will be higher in the middle.

Remember, optimum precipitation rate is obtain with the right pressure. You will get optimum precipitation rate with pressure regulated rotors.

Welcome to the neighborhood!

post by nvanlaar on Apr 19, 2021

Yeah, yeah, this is super old, but here’s an added explanation if anyone comes looking:

Rainbird/Hunter/etc MPR nozzles will have a different precip rates for fulls/halves/quarters/etc. because of the motion. Think about it, a quarter head will sweep the same area 4 times for every one rotation of a full circle rotor. A half rotor will sweep the same area twice for every full circle rotation. This is the problem with contractors just throwing the same nozzle into every rotor regardless of the pattern. This is why a lot of times if you took an aerial photo of a school yard, there will be rings in the grass. The scheduling is set to the perimeter heads and the center full circle rotors will be underperforming comparatively. You should be safe using the full circle precip rate of a mixed zone as a starting point if the nozzles are matched correctly.

post by tmcgahey on Apr 19, 2021

Yea, rotors are a totally different animal when it comes to setting up. They take the most planning to match nozzles, usually they come with multiple nozzles to match precipitation numbers for full, half, and less.

post by Gerardv514 on May 28, 2021

Recently had a system installed using rain bird 5004+ rotors. They came with an orange 2.0 nozzle. Any recommendations on which to use for full, half and 90’s?

post by JBEng318 on May 29, 2021

Here’s a link to Rainbird’s nozzle performance chart:

5000-series-rotor-nozzle-performance-chart.pdf (rainbird.com)

I’m not sure what series you have since I can’t find any orange nozzles on their site.

But according to this link, if we assume your 2.0 nozzle is 2.0gpm at 45psi, I’d suggest using the 2.0 for your half circles, which is the nozzle default. And the 4.0 nozzle for your full circles.

1.5 could be used for the 1/4 circles.

Please anyone correct me if I’m mistaken.

post by Gerardv514 on May 29, 2021

I was having the same issue too. Have no idea where the orange nozzles came from, but they definitely say 2.0. I have some of the regular nozzle trees which are blue.