The Tuna Can Test: A Simple Trick to Water Smarter and Protect the Lagoon
Did you know that you might be watering your lawn more than it needs?
Overwatering your yard doesn’t just waste water. It also sends excess fertilizer and nutrients deep below your lawn’s roots, where they can become groundwater pollution instead of helping your plants grow. At the same time, excess water running off your lawn carries these nutrients into streets and storm drains, where they flow untreated into canals and directly into the lagoon. This stormwater pollution contributes to harmful algal blooms, seagrass loss, and muck buildup in the Indian River Lagoon.
Luckily, there’s an easy and nearly free way to check how much water your sprinklers are putting out. It’s called the Tuna Can Test—and yes, it really involves a can of tuna.
What Is the Tuna Can Test?
The Tuna Can Test is a simple way to measure how much water your irrigation system delivers during a typical cycle. You don’t need any fancy tools—just a few small, shallow cans like empty tuna or cat food cans, a ruler, and 15 minutes of your time.
By doing this test, you’ll find out how long your sprinklers should run to deliver just the right amount of water—not too much and not too little.
Why It Matters for the Lagoon
When your irrigation system runs too long, it applies more water than your lawn can absorb. That excess water mixes with fertilizers and other yard chemicals and carries them into the groundwater—or worse, directly into the Indian River Lagoon through the stormwater system.
Excess nutrients from overwatering can lead to:
- Harmful algal blooms that block sunlight and lower oxygen levels
- Seagrass loss, which endangers manatees and sea turtles
- Increased muck buildup, which suffocates aquatic life
By watering wisely, you:
- Prevent fertilizer runoff and groundwater pollution
- Keep your plants healthier by avoiding root rot or shallow root systems
- Reduce your water bill (or lower your water use)
- Help protect seagrass, fish, and wildlife that depend on a clean lagoon
How to Do the Tuna Can Test
What You’ll Need:
- 4–6 empty tuna cans or any short, flat-sided can of similar size
- A ruler (marked in inches)
- A timer or stopwatch
Step-by-Step Instructions:
- Place the cans
Scatter your empty cans evenly across your lawn, including different zones of your sprinkler system. Be sure to place some near sprinkler heads and others farther away to account for uneven coverage. For hose-end sprinklers, place cans in a line from the sprinkler outward (UF/IFAS Gardening Solutions). - Run your sprinklers for 15 minutes
Turn on your irrigation system for a full 15-minute cycle. Let it run as it normally would. - Measure the water
Use a ruler to measure how much water is in each can (to the nearest 1/8 inch). Record each measurement and then calculate the average depth by adding all measurements and dividing by the number of cans. - Evaluate your results
You’re aiming for ½ inch to ¾ inch of water per session:- Less than ½ inch = under-watering
- More than ¾ inch = overwatering
- Inconsistent water levels between cans = uneven sprinkler coverage, which may need adjusting
- Adjust accordingly
Use your results to fine-tune your irrigation schedule. If you’re watering too much, reduce your run time. If you’re watering unevenly, check for clogs, broken sprinkler heads, or poorly positioned emitters.
💡 Tip: Repeat the test at least once a year or any time you change your irrigation setup or landscaping.
How Often Should You Water?
Even in Florida’s dry season, most established lawns only need water once or twice a week. During the rainy season (June to September), you may not need to water at all—nature usually takes care of it!
Make sure you’re following the St. Johns River Water Management District’s watering restrictions, and be sure your system includes a functioning rain sensor (required by law for all automated irrigation systems in Florida – UF/IFAS).
Smarter Watering, Healthier Lagoon
The Tuna Can Test is a small but powerful action you can take to help protect the Indian River Lagoon. Every drop of water you save, and every ounce of nutrient runoff you prevent, contributes to cleaner water and healthier habitats for manatees, sea turtles, and over 4,400 species of plants and animals that call the lagoon home (Smithsonian Marine Station).
So before your next irrigation cycle, grab a few cans, set your timer, and put your system to the test. Your yard—and your lagoon—will thank you.
📲 Want to share your test results or get tips on irrigation? Tag us on Instagram or Facebook @LagoonLoyal!
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