The Tuna Can Test
You can't tell if your sprinkler system is running efficiently just by looking at it. You need data. The tuna can test — also called a catch cup audit — gives you exactly that. All you need are some empty tuna cans (or any same-sized shallow containers) and a ruler.
Don't just throw the cans in a random grid. Place them strategically: one in a dry-looking spot, one where you've got nice thick grass, one where weeds have taken over (weeds are a sign something died there), and a couple in between. You're comparing the good spots to the bad.
Set Out the Cans
Place 6–10 cans across one zone. Cover the area near heads, the middle ground, and the edges. Be aware of which spots might sit on the border between two zones — a dry spot there isn't necessarily a problem, it might be getting half its water from Zone 2 and half from Zone 3.
Run the Zone for 15 Minutes
Time it exactly. Let it finish, then measure the water depth in each can with a ruler. Write it down.
Read the Results
You're tracking two things: run time and coverage. For run time — you want half an inch per session. If you got a quarter inch in 15 minutes, that zone needs 30 minutes. Write that number down and tape it inside the lid of your timer box. Done forever for that zone.
For coverage — if some cans are full and others are nearly empty, you've got a head alignment problem, a clogged nozzle, or the wrong nozzle size on one of those heads.
Tape Your Run Times to the Timer
Once you've figured out how long each zone needs to run, tape that info inside the lid of your timer box. It's there every time you open it. You do this once and never have to think about it again.
The Part Nobody Tells You: Nozzle Sizing
This is why most sprinkler systems are inefficient right out of the box. Installers throw heads in the ground and leave without ever touching the nozzles. Commercial rotor heads come with a nozzle tree — a card with every nozzle size from 1.5 to 10, where the number is gallons per minute. Most installers never use it.
The rule is simple: match your nozzle to the arc each head is covering. A head doing a 90-degree corner needs a smaller nozzle than one sweeping 360 degrees. If they all have the same nozzle, your corners are getting drowned while your middles stay thirsty.
| Arc Coverage | Relative Nozzle Size | Example |
|---|---|---|
| 90° (quarter circle) | 1x (smallest) | Size 1.5 |
| 180° (half circle) | 2x | Size 3 |
| 270° (three-quarter) | 3x | Size 4.5 |
| 360° (full circle) | 4x | Size 6 |
If your system is set up in the right pattern with the right nozzles, you don't even need to do the tuna can test. But if you inherited someone else's system — do the test.
Head Placement: Two Patterns That Work
There are exactly two layouts that give you proper coverage. If your heads aren't in one of these patterns, whoever installed the system was guessing.
Square Pattern
Needs 100% head-to-head coverage. Every head throws water all the way to the next head. They're kissing. If there's a gap, you've got a dry spot.
Triangular Pattern
You can get away with 80% coverage because of how the geometry fills in. This is the more common professional layout. Either works — just don't mix them and don't improvise.
Never Mix Spray Heads and Rotors on the Same Zone
Spray heads (the little stationary misters) and rotors (the ones that sweep) put out completely different amounts of water. A spray head might dump an inch in 10 minutes while a rotor takes 40 minutes to do the same. Put them on the same zone and half your lawn is a swamp while the other half bakes. Don't do it. You can mix brands — Hunter and Rain Bird on the same zone is fine. Just not head types.
Jacksonville Watering Schedule
For watering amounts and timing, use your local university extension service — not random websites. In Florida that's UF/IFAS. They publish the actual science for your specific region, soil type, and grass variety. What works in Jacksonville doesn't apply in Phoenix or Seattle.
For St. Augustine grass on the First Coast:
Summer (April – October)
Half an inch, twice a week.
One inch total per week.
Your city sets which days you can water. They don't limit how long — figure out your run times with the tuna can test, then run it those two days.
Winter (October – April)
Once a week.
Same run time per zone — don't change that.
Just change your timer from twice a week to once a week. That's it.
Rain Sensors: Your Biggest Money Saver
Spend sixty dollars. Set it at one inch. Done.
There is no bigger waste in lawn care than a sprinkler system running in the rain. A rain sensor shuts your system off automatically when you've gotten enough rainfall. It pays for itself the first month.
Where to mount it: Out in the open. Full sun. Not under a tree, not under an overhang, not near your bird feeder. The sensor holds water in a gauge and shuts off your system. But it needs sun to evaporate that water and reset. Put it in the shade and it'll hold water for days, keeping your system off long after the rain has stopped.
Check Your System Every Quarter
Once you've got it dialed in, you just need a five-minute walkthrough every three months. Turn on each zone, walk the yard, watch every head. For rotors, wait for the full sweep left to right. Make sure it's still covering what it's supposed to cover.
Heads get knocked by mowers, bumped by cars, chewed on by dogs. The ground level shifts as roots spread and mulch builds up. Trees get cut down and shaded areas become full sun. Plants grow and block heads. What worked two years ago might not work today. Walk it quarterly and you'll catch problems before your water bill does.
For slopes, put your heads at the bottom and spray uphill. Water runs downhill — work with gravity.
Related Pages
Just installed new sod? Follow our new sod care guide for the first 30-day watering schedule. Questions about installation? See our installation process.