Measuring Your Sprinkler's Water Use
You may have heard the phrase "water lawns 1 inch a week." While this is a good rule of thumb, it is based on your lawn’s water needs as averaged throughout the year.
Our typical Pacific Northwest summers tend to be long, hot, and dry with rainfall at a minimum. Therefore, it is likely that your landscape may require more water during the summer months and less water during the spring and fall months when the weather tends to be rainier and cooler.
The key to watering efficiently is to frequently adjust the amount you water throughout the growing season as the weather and your plant’s water needs change.
To Do This You Will First Need To Know
- how quickly your sprinkler distributes 1 inch of water¹
- set a base schedule
- and adjust the watering schedule on a weekly basis using the Consortium’s Weekly Watering Number
Four Easy Steps To See How Long It Takes Your Sprinkler To Water An Inch:
- Place two Consortium watering gauges at two different places within your sprinkler’s spray range. Then run your sprinkler for 15 minutes². (You may also use a tuna can and a ruler to conduct this test)
- Find the average amount of water (in inches) collected in your gauges. To do this, measure the amount of water in each gauge. Add these amounts together and divide by two. This is the average amount of water your sprinkler puts out in 15 minutes.
(This will provide you with a good guideline amount. For increased accuracy, repeat steps 1 & 2 several times, placing the gauges at different distances from your sprinkler.)
- Use this chart to see how much time it will take you to water one inch.
Total time needed
1/8" = 120 1/4" = 60 1/2" = 30 3/4" = 20 1" = 15
- Set your base schedule. We recommend watering 2 times per week, either before 10 a.m or after 6 p.m when temperatures are cooler.
For example, if after 15 minutes your gauges have 1/2 an inch of water in them, you will need to water a total of 30 minutes per week to get the recommended 1 inch.
M T W T F S S Minutes 15 15
How to use a watering gauge to measure your sprinkler's water use
Take The Next Step:
If you have an automatic sprinkler system, you will need to program this base schedule into your sprinkler’s controller. Then you can use the Weekly Watering Number to fine tune your system’s settings to water your landscape as efficiently.
¹ An established lawn needs about 1 inch of water each week and more during hot, dry spells. However, water needs vary from plant to plant, so it is best to check with your local garden center or landscape professional on your plant’s specific watering needs.
² If run-off occurs, you will need to run your sprinkler for a shorter time period so that you are applying only the amount of water that your soil can absorb. Use watering gauges to figure out how much water your system distributes during this time, and then figure out how many times you will have water each week to put down the recommended 1 inch per week.