Using a Catch Cup Test to Optimize Advanced Zone Settings

Last Update: Apr 21 2026 5:04pm • Est. Read Time: 7 MIN

Measure how much you’re actually watering

Do you know how much water your sprinklers are actually applying to your lawn? Your sprinkler heads will have a manufacturer’s estimate (e.g. 1 inch per hour), but this depends on the state of your sprinkler heads, valves, lines, and even your water pressure -- it’s just a rough estimate!

You can measure the precipitation rate and uniformity of your sprinklers with a catch cup test. This is commonly performed by an irrigation pro, but you can do it yourself with 30 minutes and some basic equipment, following the steps outlined in this guide. There is a little bit of math involved, but we've made Google Sheet template that will do the math for you! You can make a copy and use it when it is referenced later in the guide. To make a copy, simply click the link, then click "File" > "Make a copy" (if you'd like to save it to your own google drive), or "Download" (if you'd like a copy saved directly to your computer).

The measurements

There are two important metrics you can learn by doing a catch cup test, and one requires more precision than the other.

Efficiency (AKA Uniformity) is a measurement of how evenly your sprinkler heads distribute water across your zone. You can measure uniformity by simply measuring the depth of water collected in catch cups (this is easier to do, and less precise).
Nozzle Inches Per Hour (AKA Precipitation Rate) is a measurement of how much water your sprinklers are applying to your zone. This rate is expressed in inches per hour, so is directly comparable to natural rain and evapotranspiration. Rachio has set up your zone with a default rate based on manufacturers averages for the type of sprinkler head you selected for the zone. You can use the measurement you make with a catch cup test to update your zone settings and achieve more accurate watering.

This requires a higher degree of precision and a bit of math. To make this measurement we recommend you use either graduated catch cups, or DIY containers with a graduated cylinder to measure volume.

Note

Let's walk through both methods. If this sounds too technical, rest assured that both methods can be easily performed by any homeowner with some simple tools and a bit of math.

Get together your materials

Choosing catch cups

You’ll have the best chance of making accurate measurements if you purchase professional catch cups with milliliter measurements (about $40 for a 12-pack), but you can perform a pretty accurate audit with a set of uniform containers (e.g. pie tins or tupperware) and very careful measurements. See the note below this article for tips on choosing catch cup.

Materials

8-12 catch cups* (see description below)
Ruler or tape measure
Time piece (phone, watch)
Notebook and pencil
Graduated cylinder (ONLY needed for measuring volume with DIY catch cups)

When to do the audit

For these measurements to be most representative of your normal watering, make them during the approximate time of day (within a few hours), and without additional household load (no dishwasher, washing machine, or showers running)
Choose a day that is not particularly windy (wind >5 mph can lead to inaccurate measurements)

Setup and measurements

Perform this one zone at a time

Visually inspect your system for obvious problems. In many cases, an initial visual inspection can detect obvious problems that can be corrected, which will greatly improve the performance of the irrigation system. Turn on the system and watch it run. Are there broken sprinklers or obvious adjustments needed (heads not popping up all the way, clogged heads, or heads pointing in the wrong direction with water falling on the sidewalk instead of the lawn)? Are there obstructions preventing water from reaching the intended target (tree trunks, overgrown grass, weeds, or overhanging shrubs)?
Fix problems. Repair problems before proceeding further. For many sprinkler heads the nozzles can be individually replaced. If necessary, consult with a landscaping contractor.
Set out catch cups. The idea is to uniformly distribute catch cups on your zone to best sample how the sprinklers are watering. This is more art than science, and not all zones are the same shape, so following some basic guidelines will yield good results. Start by placing a cup 2 feet away from each sprinkler head, towards the center of the zone. Then place additional cups at half-way intervals between those cups. If space in the interior of the zone remains empty, place cups in it, again at half-way intervals. Step back from a distance and check that the cups look more or less evenly distributed (precision here is not necessary). 8-12 cups works well for most residential zones (very large zones might need more).
Run the zone you're testing for 20 minutes. E.g. run a Quick Run on your Rachio. 20 minutes usually produces enough water to measure accurately, but you can test for a different time period; measure it well. If you can see wind blowing the spray around, consider waiting until a less windy time.
Measure and record. For graduated catch cups, record the volume in mL. For DIY catch cups, you either measure the volume of collected water with a graduated cylinder, or you measure the height of the water in inches, being VERY careful that the cup is level and the water is still.

Note

Write down the measurements or any conversions on your map or notebook, taking care not to double-count any cans (the map helps keep this organized).

Calculations

There’s a bit of math here, but we’re making it easy. You make a copy of this Google Sheet template and enter your data; it will do the calculations for you.

For those interested in how these calculations are made, this is what we’re doing:

Convert volumes to linear inches.

If you’re just measuring uniformity, you can skip this step.

To convert the volumes you measured into units you can compare with precipitation, you need to do a bit of math. Measure the diameter of the mouth of the catch cup in inches and use Equation 1 to calculate the area in square inches. For rectangular DIY containers, area is simply length x width.

Then calculate the inches watered:

Calculate nozzle rate. Divide the sum inches of all catch cups by the total number of cups to get the average. Then standardize this average rate to an hourly rate: i.e. if you ran your test for 20 minutes, multiply the rate by 3 (20 mins x 3 = 60 mins) to get a nozzle rate in inches per hour.
Calculate uniformity. Arrange the catch cup data from smallest to largest (this can be mL, inches, or rate, as long as you use the same metric for all cups). Calculate the average of the lowest quarter (25% of the catch cups that collected the lowest amount of precipitation). If you used 12 catch cups for your irrigation audit, you need the average volume of the three cups that collected the least amount. Divide the lowest quarter average by the total average. This gives you the lowest quarter distribution uniformity as a fraction (multiply by 100 to get a percent %).
Apply your measurements. So you’ve gone to the trouble to make these measurements, now you’re ready to improve your irrigation with what you’ve learned. First, assess your uniformity according to this table (source: NM State University Extension)

If your uniformity is Fair or Poor, you probably cannot expect a healthy lawn in this zone, no matter how much water you run through the sprinklers. Consider fixing coverage problems before increasing your watering.

If your uniformity is Good or above, you can calibrate your zone settings to optimize your irrigation. In zone advanced settings, we’ve started you off with a default “nozzle inches per hour” rate based on manufacturer’s estimates in ideal average conditions, but these often don’t match real life. Update your "nozzle inches per hour" setting and enjoy more accurate irrigation.

Enjoy! You now have the most accurate data on your block, and the intelligence of Rachio on your side. Enjoy your healthy lawn while knowing you're using just the amount of water you need for your irrigation - and no more.

An additional note on choosing catch cups

Making precise measurements of sprinkler precipitation is hard because the volumes of water are small. We highly recommend purchasing a pack of graduated catch cups (about $40 for a pack of 12) to perform your irrigation audit. These cups are designed specifically for this purpose; their advantages include:

Cups staked into the ground at a uniform height are best positioned to sample your sprinkler pattern evenly.
Conical design increases accuracy when measuring small volumes.
Wide funnel aperture compensates for under-reporting from a high-sided vessel which only captures precip falling directly vertically into the cap.

That said, many people have performed an audit successfully with DIY containers. Using household containers requires more care in both setting out the cups and measuring. Ideally, all cups will be identical, with flat wide bottoms and short sides, and be either circular or rectangular so area is simple to calculate. Pie tins work well for this purpose, or a matching set of tupperware. People have done this with tuna and cat food cans, but we’ve found the wide pie tin work better. Some tips for using DIY containers:

Get a set of cups as identical as possible
Go for wide, flat, short containers
Do your best to get each container level on the lawn. You can use small pebbles or metal nuts to weigh them down; these will not affect volume measurements, but will cause you to underestimate a direct linear inches measurement very slightly, so choose small pebbles for this.

With care, you can make accurate measurements of precipitation in linear inches (i.e. with a measuring tape), but the container must be perfectly level and the water still. If you have any doubts about these measurements, measure the volume in a graduated cylinder and convert to linear inches following step #7 above.