Improving Uniformity and Efficiency - Catch Cup

This is less a Rachio problem and more a “new to irrigation and lawn care” problem with me.

We bought a house with an existing 6 zone irrigation system in USDA zone 6b with cool weather grass. Previous owner hadn’t run the system in at least 10 years, so I replaced the controller with a Rachio 3, but had a contractor come out to do the startup, fix any leaks and replace any shot heads. They offered to show me how to replace the heads and just recommended going to the local big box to pickup new rotors. I picked up 12 x Rainbird 42SA, replaced them all and then really poorly adjusted the coverage area.

Long story short, I ran a catch cup test last night. I have 5 zones with uniformity between 34-42% and 1 at 52%. Precipitation rates range from .56" to 1" per hour. Using a less precise measurement, I can see areas of significant overlap and other areas are completely being missed.

Help? I’m not sure if I should look at different heads, nozzles or just adjust the pattern and distance – but I’m here as much for the water efficiency as I am a healthy lawn.

In an ideal world, you would have head to head overlapping coverage. That is really hard to get, which is why you will never see 100% uniformity, but 40% is very low. I believe those Rainbirds have a decent amount of adjustability in the arc throw. Might just need to play with things to see if you can get that uniformity up!


Thanks for the response and here’s (one of the spots?) I’m getting tripped up.

Rainbirds have a screw at the top that can be adjusted to obstruct and diffuse the spray. Is arc spray the same thing? If it is, I get a good amount of pooling near the sprinkler head when I start to close it. If it’s wide open, no pooling.

It’s probably worth mentioning the 42SA+ has a throw range of 26’-38’. My yard is approximately 60’ east to west and 50’ north to south. All sprinklers are on the perimeter, with one at each corner and one halfway from each corner. There are no sprinklers in the middle of the yard. Sprinklers in the corner are going about 90 degrees, the other four are going 180 degrees. Here’s a bad diagram of the front yard.

Considering that, should I be using different valves around the yard?

Are rotors (vs rotary) the right pick?

Based on your yard layout, you will definitely need to use most of that sprinklers throw to get the distance needed. Are the colors representing zones, so 3 zones for the front yard?

Rotor setup can be tricky. I’m not sure how your technicians installed the new Rainbirds. If all the rotors have the same gpm rate, the 90 degree will put out twice what the 180 will since it takes half the time to complete a full sweep. What you need to do is match the nozzles accordingly. In your case, you might need to throw a 1.0 nozzle in the 90 heads, and a 2.0 in the 180s. Or, if you have enough GPM, you could do 1.5’s in the 90, and 3.0 in the 180s. This would balance out the precipitation rate better, along with making sure that you get full head to head coverage.

And yes, that screw is adjusting the throw, or the arc of the sprinkler.


They showed me how to replace one and then encouraged me to take on the rest. I must have missed the common sense part about 90s putting out twice as much as the 180s. They’re all using the standard nozzle, which I think is the 3.0. That sounds like a great place to start tinkering – along with thinking about GPM per zone and head (eg, red/blue having 3, green only 2).

Thanks so much for your patience and help. You saved me from just guessing and doing something like swapping in rotary sprayers :upside_down_face:

1 Like

Where are the spots that the sprinklers got head to head (e.g. all corners touch the adjacent middle, all middles touches the corners, but the middles do not touch the opposite middle)? Also, where are the biggest differences in uniformity?

Depending on the answers to the above and @tmcgahey’s question & how the corner nozzles are doing, I would probably add a nozzle in the middle of the yard to help with the coverage. Of course, that would be about 25’ of digging.

I will say that I really like my Hunter MP Rotator nozzles and know Rachio sells the K-Rain Fully Adjustable Rotary Nozzle, which I heard are rather similar.

Agree with @Thomas_Lerman that at least one head in the middle would be ideal, but if you can get the precipitation rates balanced (switching the 180’s to 1.5 nozzles), and head to head coverage achieved, I think you’ll find that uniformity tighten up a ton!

I also agree with @Thomas_Lerman here too, but you’ve already invested in the new rotors, so you can work with them! Rotary nozzles are nice because you don’t have to worry about mixing and matching nozzles for the different sweeps. The full amount of water sprays out across the full sweep, regardless of what that sweep is.

1 Like

Note to self: @tmcgahey agreed with me twice in the same posting. Totally kidding, I appreciate you. I agree with already invested in new rotors.


Yes, you’ve got that exactly right. Corners hit the adjacent middle, middle hits the corners, middle to middle (north to south long edges) get about 60% across to the opposite middle, the east west short edges only go about 25%.

Here’s a visual. The ovals are the area of low precip. The higher precip is along the edges where the heads are able to reach the adjacent heads. Zone 1 (green) has the highest uniformity – but only at 41%. Zone 3 (red) is at 38% and zone 2 (blue) is at 34%.

Adding another head is out of scope for the time being – and surprisingly the areas of least uniformity don’t look under watered. I’m really just trying to minimize consumption by improving the efficiency with what I’ve got.

I’m not opposed to switching heads out – but I’m confused by the rotary options. For example, the K-Rain’s specifically say “spray body not included,” but I’m not sure how to find the matching part to that. I’m under the impression I can’t swap the rotary nozzles onto a rotor head. Is that right?

Appreciate the help from you and @tmcgahey! Mighty generous of you both.

…oh, and I’m starting to wonder if there’s a buried head we haven’t found in the middle of the yard. It’s my (deceased) grandfather’s house that he meticulously built back in the 40s with an annoying amount of precision. I hadn’t really thought about it until now, but I have a hard time believing he (or my grandmother who literally cut the lawn around pavers with scissors) would have let some knucklehead contractor get away with no coverage in the middle of the yard :joy:

Nozzles just showed up yesterday, so I’ll let you know how things land.

Keep working with what you have first. Swap the nozzles on those 90’s down to balance things out and see what happens. Your uniformity “map” makes total sense. Those oval areas would be where you have the least overlap in the sweep of each sprinkler.

But, IF you decide to change things out, the rotary heads are replacement heads for a basic pop up sprinkler body, so you would have to buy new bodies, as well as the sprinkler nozzles.

@Albs Assuming you have the standard nozzles this is how I’d start out the nozzling. You should have sufficient volume to run each zone ( 7.5 GPM being worst case )

Here’s a quick sprinkler overlap map:
Blue = 5 heads
Cyan = 4 heads
Green = 3 heads
Yellow = 2 heads

The stream of water tapers off (usually) at the end of throw and your dry spots have the most overlap.


Not all the arcs were easy to tell where they were originating from (I incorrectly thought two were missing until I counted the ends & then found the “missing” arc) Cool graphics. What you provided made sense to me. What did you use to create them? I just might do one for my yard for the fun of it and see what I can learn. I am curious how the theoretical matches @Albs’s observation.

@Thomas_Lerman I created the graphics in AutoCAD using software I wrote :). I’ve been doing commercial irrigation design for about 23 years now.

I do agree that the arcs on the bottom graphic are hard to read as they are doubled up with different radii.

Curious as to what sprinklers you’re using in your yard? If CIT has profiles for them I can model your layout for you if you make a diagram with spacings and nozzle pressure.

They look something like this:


I use Hunter MP Rotators nozzles with the Hunter PRS40 pop-up bodies. I believe the only thing left would be to measure the radius that I have adjusted for each head which would be easy, just take a little time when I can.

As I think about it, I believe it would be pretty easy for me to do as well. I have my diagram all in a KML. Actually, I probably need to do some updating since I split two zones to make a third. KML does not do well with arcs, but I have applications I have wrote to create them and believe tools exist.

I used to have these in my yard as well. Then I tried out the Rain Bird RVANS for a bit but found them to be too fragile for my weed whacker :slight_smile: … now I’m back to Rain Bird 3500-SAM and my yard has not looked better.

I GPS’d my MP’s a few years back and modelled it. Came out to about a 75% DU … pretty good.