Take 15 minutes today to see how long it takes your sprinkler to water an inch and you'll be set to water efficiently all summer long!
One of the reasons many people overwater is that they don't know how much water their sprinkler uses. You can easily figure this out if you have two or more tuna (or similarly-shaped) cans, a ruler, 15 minutes, and some basic math.
Once you know this, you can use the Weekly Watering Number to adjust how much (or little) you water your landscape or garden each week throughout the summer.
How to measure your sprinklers' water use:
Put one tuna can about 1.5 – 2 feet away from your sprinkler head.
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Put a second can at the end of that same sprinkler head’s reach, around 1 foot from the edge of the spray. If you are using more than two cans, spread them out so that they are at different distances from the sprinkler head (close, midrange, end of spray pattern).
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Run your watering system for 15 minutes. If puddling or runoff occurs, time how long it takes for that to happen. Use that time instead of 15 minutes. If you have more than one watering zone, you may want to do this for each zone.
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Use a ruler to measure how many inches of water are in each can.
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Add the amounts from each can together.
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Divide the total amount of water from both cans by the number of cans. This is the average amount of water that your sprinkler uses in 15 minutes.
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For example: 0.75” + 0.25” = 1”
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1” ÷ 2 cans = 0.5”
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0.5” after 15 minutes = 30 minutes needed to water 1"
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- Use this chart to see how much time it will take you to water one inch:
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Average water depth in inches after 15 minutes
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=
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Total time needed to water 1 inch
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|---|---|---|
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1/8" (0.125")
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=
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120
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1/4" (0.25")
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=
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60
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1/2" (0.5")
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=
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30
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|
3/4" (0.75")
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=
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20
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1"
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=
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15
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Why is it important to know how long it takes a sprinkler to water an inch?
One inch is the average amount of water that grass needs each week during the summer. Once you know how long it takes to water an inch, you can use your system’s controller to set a base schedule. Then you can use the Weekly Watering Number adjust the amount of water you give your landscape each week throughout the watering season.
How to measure the amount of water used by other types of watering system or methods
Use the same instructions as above with the following variations:
- Soaker hoses: You can measure the amount of water used by soaker hoses by placing the cans in two locations along your hose.
- Drip systems: Place one can under each type of emitter that your system uses. This method works best with uniform emitters (all emitters on the line have an output of 5 GPH).
- Watering by hand: You can measure the amount of water used when hand-watering with a hose nozzle or sprinkler by timing how long it takes to fill up a bucket. For example: if it takes two minutes to fill up a five-gallon bucket, you know that your hose nozzle or sprinkler uses 2.5 gallons per minute.