How Long to Run a Sprinkler for 1 Inch of Water (Catch-Can Test)

Last updated: October 2026 · Written by the LawnVibe editorial team.

"Water an inch a week" is the most common lawn advice, but sprinklers do not come with an inch counter. A spray zone might deliver an inch in under an hour, while an oscillating sprinkler on low pressure might need two. Knowing how long to run sprinkler for 1 inch of water in your own yard takes a simple test with a few cans and a ruler. This guide walks through that test, gives typical run times by sprinkler type and shows how to turn the result into a weekly schedule.

For the bigger picture, see our main guide on how to water your lawn.

Why 1 inch?

The number comes from how deep water needs to go.

About an inch of water a week, including rain, wets the soil several inches deep in most lawns, which is where grass roots grow. It is a good baseline for established lawns in the growing season. In hot, windy summer weather, needs often rise to around 1 to 1.5 inches. In spring and fall, rain may supply most of it.

What "precipitation rate" means

Irrigation professionals describe sprinkler output as a precipitation rate, measured in inches per hour. A spray zone might apply water at well over an inch per hour, while a rotor zone may apply less than half an inch per hour. The higher the rate, the shorter the run time needed for an inch, and the greater the risk of runoff on slow-draining soils. The catch-can test is simply a home method for measuring your precipitation rate.

Typical run times by sprinkler type

These are rough ranges only. Actual output depends on water pressure, nozzle size, head spacing, how much area each head covers and even the time of day. The only way to know your number is to measure.

How long to run a sprinkler for 1 inch: the catch-can test

What you need

• Six to ten straight-sided containers, such as tuna or cat food cans, plastic cups or purpose-made catch cups
• A ruler marked in inches or fractions of an inch
• A timer
• Notebook or phone for results

Step 1: Place the cans

Set the containers around one zone or one hose-end sprinkler's coverage area. Put some near the sprinkler, some at the edge of its reach and some in between. For in-ground zones, place cans between heads as well as near them.

Step 2: Run the sprinkler

Run the zone or sprinkler for a set time, usually 15 or 20 minutes. Avoid windy times, which distort results.

Step 3: Measure

Measure the water depth in each container with the ruler. Write down each reading.

Step 4: Average the results

Add the readings and divide by the number of cans. This average is how much water that zone applies in your test time.

Step 5: Calculate run time for 1 inch

Divide 1 inch by the average depth, then multiply by your test time.

Example: in 15 minutes, the average is 1/4 inch. One inch divided by 1/4 is 4, and 4 times 15 minutes is 60 minutes. So that zone needs about 60 minutes to apply 1 inch.

Repeat the test for every zone or every sprinkler position, since output varies widely.

Tips for an accurate test

• Use identical, straight-sided containers. Sloped cups make measuring harder.
• Test in the early morning, when you normally water and winds are calm.
• Run the full system as usual, so pressure matches normal conditions.
• Use more cans for large zones, at least six to ten.
• Measure promptly before water evaporates.
• Write results by zone, with the date.

For very small amounts, a ruler marked in eighths or sixteenths of an inch helps, or pour the water from each can into a measuring cylinder and convert.

Using a rain gauge instead

A simple rain gauge placed in the middle of a zone gives a rough reading, though a single gauge cannot show uneven coverage. Many homeowners keep a rain gauge in the yard year-round anyway to track rainfall, which makes it easy to know when to skip watering. Combining a rain gauge for rainfall with a one-time catch-can test for each zone covers both needs.

Reading uneven results

If some cans hold far more water than others, coverage is uneven. Common causes include:

• Clogged or damaged nozzles.
• Tilted or sunken heads that spray into the grass.
• Heads spaced too far apart, leaving dry gaps.
• Low or high water pressure, which distorts spray patterns.
• Mixed head types on one zone, such as sprays with rotors.
• Wind during the test.

Fixing these problems saves water and evens out the lawn. For a full system check, see our guide on how to do a sprinkler audit.

Turning the result into a schedule

Your catch-can number is the foundation of an efficient schedule.

Once you know how long each zone takes to apply an inch, split that time across your watering days.

• Two days a week: about half the 1-inch time per day.
• Three days a week: about a third of the 1-inch time per day.

Example: a zone that takes 60 minutes for an inch, watered twice a week, runs about 30 minutes each time.

Adjust for season and rainfall. Our lawn watering schedule guide shows sample schedules for clay, loam and sand, and how often to water a lawn covers frequency.

Watering new seed and sod

The 1-inch rule applies to established lawns. New seed needs only light watering to keep the surface moist, often just a few minutes per zone once to three times a day until it sprouts. New sod needs enough water to soak through the sod and into the soil below, usually daily at first. Use your catch-can results to set these shorter runs accurately, then return to the established schedule as the new grass roots in.

Cycle-and-soak for clay and slopes

Spray heads in particular often apply water faster than clay soil can absorb it. If water runs off before the zone finishes, split each run into two or three shorter cycles with 30 to 60 minutes between them. Most controllers can do this automatically. Total minutes stay the same; the water just has time to soak in.

Checking that water reaches the roots

Run time is only useful if the water actually soaks in.

After watering, wait an hour and push a long screwdriver or soil probe into the lawn. If it slides in easily about 6 inches, water reached the root zone. If it stops after an inch or two, the soil is still dry below and you may need longer or slower watering. Our guide on how to check soil moisture in a lawn covers more tests.

Hose-end sprinklers

The test works just as well without an in-ground system.

Run the catch-can test for each position where you place a hose-end sprinkler. Impact and oscillating sprinklers vary with water pressure and the coverage setting you choose. Once you know the time, use a faucet timer to shut off the water automatically. Overlap positions slightly to avoid dry strips. Our roundup of the best impact sprinkler compares hose-end models that cover large areas evenly.

Run times by soil type

The catch-can test tells you how fast water lands; soil determines how fast it soaks in.

• Sandy soil absorbs water quickly, so runoff is rare, but water drains below the roots if you apply too much at once. Split the weekly inch into three sessions.
• Loam absorbs water at a moderate rate. Two sessions a week usually work, with little need for cycle-and-soak except on slopes.
• Clay absorbs water slowly. Even rotors may need two or three cycles per session to avoid runoff.

Matching run times across zones

Each zone on an in-ground system usually needs its own run time:

• Spray zones apply water fastest and need the shortest run times.
• Rotor zones apply water slowly and need longer run times.
• Shaded zones need less total water than sunny ones.
• Slopes need shorter cycles repeated more often.
• Narrow strips along driveways and sidewalks often use small spray nozzles and dry quickly in heat.

Avoid mixing spray heads and rotors on the same zone, since they apply water at very different rates. Our guide on sprinkler zone run times explains how to set each zone.

Adjusting for rain and season

Subtract rain from the weekly inch. If a storm drops half an inch, cut that week's watering by about half. In spring and fall, many lawns need less than an inch of irrigation, while in midsummer heat they may need a little more. Seasonal adjustment features on many controllers let you scale all run times up or down by a percentage instead of changing every zone. See seasonal sprinkler adjustment.

Common mistakes

• Guessing run times instead of measuring.
• Using the same time for every zone.
• Testing on a windy day, which skews results.
• Measuring only near the heads, where cans fill fastest.
• Running the full time on clay in one go, causing runoff.
• Never retesting after repairs or seasons change.

How often to retest

Retest each spring, after any system repair or nozzle change, and if you notice dry or soggy patches. Water pressure can change over time, and heads shift as soil settles.

University extension services, such as Texas A&M AgriLife Extension, describe catch-can audits as a simple way to improve lawn irrigation efficiency.

The bottom line

To find how long to run sprinkler for 1 inch of water, place several cans across each zone, run it for 15 or 20 minutes, measure and average the water collected, then divide 1 inch by that average and multiply by the test time. Split the result across two or three watering days, use cycle-and-soak where water runs off, and retest each season so your lawn gets the inch it needs without waste.

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