You've Probably Never Heard of the Tuna Can Test, But it Will Stop You from Killing Your Lawn This Spring
Lawn experts swear by this easy, low-tech method for healthy grass
Are parts of your lawn browning while others are thriving? Are you unsure how long to run your irrigation system? If so, there’s a surprisingly low-tech way to find out what’s really happening with the water in your yard. It’s called the ‘tuna can test', and lawn experts swear by it.
Your grass could appear lush and thriving, at least from a distance. But looks can be deceiving. Deploying a handful of empty cans across the grass can reveal whether your lawn is being watered evenly. And if not? You have options for how to fix it and save water.
Article continues belowWhat Is The Tuna Can Test?
‘The tuna can test is a simple way to measure how much water your sprinkler system is actually putting down and how evenly it is distributing that water across a lawn,’ says Fred Trejo of Tierra Viva LLC.
‘The idea is straightforward: You place several identical cans around a sprinkler zone, run the irrigation system for a set amount of time, and then measure how much water collects in each can.’
Lawn care professionals have relied on variations of this method for years. ‘The tuna can test is a simple catch-can method for measuring how much water your sprinklers apply and how evenly they apply it,’ says Jason Keeley of Mowing Magic. 'Place several empty tuna cans around a sprinkler head zone, run the sprinklers for a set time, then measure the water collected.’
While irrigation professionals often use specialized tools to evaluate sprinkler performance, Trejo says the tuna can offers a practical substitute for homeowners. ‘This method has been used in irrigation and turf management for many years,’ he explains.
‘Professionals often use specialized catch cups and gauges to measure sprinkler performance, but homeowners rarely have that equipment available. The tuna can become the popular alternative because it is something most people already have at home and it provides a consistent container that makes it easy to compare water levels from one spot in the lawn to another.’
If precision is what you’re looking for, Orbit sprinkler catch cups available at Amazon are a convenient way of measuring sprinkler output in your yard.
Why It Works
At its core, the tuna can test works because irrigation systems apply water at a measurable rate. ‘The goal is not laboratory level precision,’ Trejo says. ‘What you really want to understand is how evenly your sprinklers are watering and roughly how much water they are delivering over time.’
Knowing how much water your irrigation system is applying can help you accurately supplement rainfall, which you can measure using a rain gauge such as the La Crosse rain gauge available at Walmart.
The shape and uniformity of the cans make them surprisingly effective measuring tools. ‘A tuna can happens to be a very practical tool for this,’ Trejo says. ‘It has straight sides, which makes measuring the water depth easy and accurate. The cans are also uniform in size, so when you use several of them you can directly compare how much water each location receives.’
Keeley agrees that consistency is what makes the method useful. 'Because all cans are identical, you can compare them to see coverage uniformity across the zone, he explains. ‘You’re not trying to measure pressure; you’re measuring applied water, and a simple container is a great way to do that.’
‘When you spread them around the lawn, Trejo adds, ‘they essentially become small collection gauges that show how the sprinkler pattern is performing across the entire zone.’
How To Do The Tuna Can Test
The beauty of the tuna can test is that it requires almost no special equipment.
- Start by selecting one irrigation zone to evaluate. ‘If you have areas of the lawn that seem to dry out faster than others, begin with that zone.’
- Next, gather identical containers. Tuna cans are commonly used, but any straight sided containers of the same size will work. The key is that they are all the same.
- Distribute them across the watering area. Keeley suggests spreading them widely: ‘Place 6–12 cans evenly around one sprinkler zone at a time to test. Include spots near the sprinkler head, midway, and near the edge of coverage. Be sure to keep them away from shrubs or overhangs that block spray.’
- Run the sprinkler system for a set period. ‘For spray heads, 15 minutes usually works well,’ says Trejo. ‘For rotor style sprinklers, thirty minutes is often better since they apply water more slowly.’
- Measure the water depth in each container and record each measurement.
- Finally, calculate the average. ‘Add all the measurements together and divide by the number of cans,’ Trejo explains. ‘If you ran the zone for fifteen minutes, multiply that average by four to estimate the inches of water applied per hour. If you ran it for thirty minutes, multiply by two.’
Interpreting Your Results
The tuna can test reveals more than just how much water your sprinklers apply. It also shows how evenly that water is distributed. Ideally, the measurements should be relatively consistent. ‘If most cans have a similar amount of water, your coverage is good,’ Keeley says.
Trejo adds that professionals often look for reasonable uniformity across the zone. ‘If most of the cans are within about 25% of the average measurement, the distribution is generally considered acceptable for a residential irrigation system.’
Large differences between cans signal a problem. ‘If you see big differences (some nearly full, others barely wet) that’s a coverage problem, not a run time problem,’ Keeley says.
Uneven results often point to fixable issues. ‘Sprinkler heads may be tilted, partially blocked by grass or plants, or clogged with debris,’ Trejo explains. ‘Sometimes the wrong nozzles are installed, or different nozzle types are mixed within the same zone.’ A sprinkler repair kit such as the Orbit sprinkler tool kit at Home Depot can help you adjust and fix most sprinkler head problems.
Once coverage is corrected, the test can help fine-tune watering schedules. ‘By knowing roughly how many inches of water a zone applies per hour, you can adjust run times so the lawn receives the right amount of irrigation rather than relying on guesswork,’ Trejo says.
In an era of smart irrigation controllers and weather-based apps, the tuna can test feels almost charmingly analog. But it’s effective because it measures what truly matters: how much water is actually hitting your soil.
For homeowners trying to conserve water, lower utility bills, and maintain a healthy lawn, this low-cost test offers clarity. Sometimes, the smartest lawn care solution isn’t high-tech at all but it’s simply taking a closer look at what’s landing in the can.
Fred Trejo is the owner of Tierra Viva Landscapes, a Dallas-Fort Worth landscaping company specializing in residential and commercial landscape care.
Jason Keeley is a seasoned lawn care professional and robotic mower expert with a passion for innovation in outdoor maintenance. He launched Mowing Magic in 2019 to help homeowners and businesses to achieve perfectly manicured lawns with less effort.
