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Catch-Cup Sprinkler Audit

How much water are your sprinklers actually putting down?

The tuna can test is the industry-standard way pros audit sprinklers. Takes 15 minutes, costs you nothing, and gives you a number that actually matches what's hitting your lawn — no manufacturer marketing, no guessing.

How to run the test

  1. 1
    Grab 3–5 tuna cans
    They're ~3" diameter and straight-sided — perfect for this. Flat-bottom cat food cans or straight-sided coffee mugs work too. Do not use cups with sloped sides (measurement error).
  2. 2
    Place them across ONE zone
    Spread them out — one near a head, one in the middle, one at the far edge. Measures both output AND uniformity (a missing or clogged head will show up as an empty cup).
  3. 3
    Run the zone for 10 minutes
    Standard test length. Don't run longer — if your zone puddles at 10 min, you've also just learned about your soil infiltration rate (that's a separate problem to fix).
  4. 4
    Measure the volume in each cup
    Kitchen measuring cup with ml markings works. Write down each number, then average them. Enter the average in the calculator below.

Calculator

What's a normal number?

Head typeTypical PR (in/hr)Notes
Fixed spray1.2 – 1.8High output. Runoff-prone on clay.
Rotor0.4 – 0.6Medium output. Good for medium/large zones.
MP Rotator0.3 – 0.5Best uniformity. Slow and gentle.
Drip line0.3 – 0.6Spot-watering. Not comparable to overhead.
Bubbler0.8 – 1.2Direct-to-root. Trees, shrubs only.
If your measured PR is far outside these ranges: your sprinklers may be mis-nozzled, mis-pressured, or the heads themselves are failing. That's where a 30-minute DIY audit pays for itself.
Next step
Convert your PR into an actual watering plan — minutes per zone, split into cycles.
Open Water Budget

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