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How Long To Leave Sprinkler On? All You Need To Know

How long you should leave a sprinkler on depends on your grass type and sprinkler output. Most lawns need 1 to 1.5 inches of water per week. This roughly translates to three 20 to 30-minute watering sessions per week. You should make calculations specific to your lawn.

Don’t know how long to leave sprinkler on to grow a healthy lawn? You are not the only one! A lot of people don’t know how often or how long to water their turf. 

It’s completely understandable!

Watering plants is a tricky business because they don’t like too little or too much water, but just the right amount! 

Nailing your watering routine takes time and practice, but I will help you get started! You can learn how to water your lawn below!

How Long Should You Leave Your Sprinkler On? 6 Important Tips

Identify Your Grass

An infographic on the different typed of grass

The first thing you need to do is identify the type of grass you have growing in your backyard. There are many different types of grass out there in the world, and each has its own watering preferences

Most lawns need 1 to 1 ½ inches of water per week. But this is just a rough estimate. Once you identify your turf, you will know exactly how much to water in the active and dormant season

Generally, cool-season grasses require more water than warm-season grasses. You will need to water more in the active season and less in the dormant season. The growing season for cool-season grasses begins in the spring and lasts till fall

Warm-season types of grass are most active in the summer and winter is a dormant season for all types of grass. 

For instance, Kentucky Bluegrass is a cool-season grass. It needs roughly 1 ½ to 2 inches of water per week in the growing season and only ½ inch per week in the dormant season. 

It requires more water than the common warm-season Bermudagrass. Bermudagrass needs only 1 to 1 ¼ inches of water per week in the active season and a mere ⅛ inch in the off-season. 

Once you identify your grass, you will instantly gain confidence in your watering and you will know exactly how much water to use. Hey! You may even end up lowering your water bill!

Measure The Water Output Of Your Sprinkler 

A close up shot of  a sprinkler with water coming out from it
Image credit:

You should get to know your irrigation system too! You need to calculate the hourly water output of your sprinkler system. Here’s how you do it:

  1. Randomly place six straight-sided containers of the same size and shape on your lawn. 
  2. Turn on the sprinkler for 20 minutes. 
  3. Measure the depth of accumulated water in each container with a ruler. Write down your measurements if needed.
  4. Calculate the average water depth across all containers. You do that by adding all depths and dividing the sum by six. 
  5. To get an hourly water output of your sprinkler, multiply the average depth by three. 

If this method sounds too complicated, you can use the technique suggested by Water Use It Wisely. They have a handy calculator to determine the water output of your sprinkler. 

The easiest way to track the irrigation is by installing a flow timer on your sprinkler line. This device monitors water flow and corrects it if need be. Some even adjust the watering schedule according to rain.

Here is a tutorial on how to calculate sprinkler’s water output: 

Calculate How Long To Leave Your Sprinklers On 

A series of water sprinklers sprinkling water on a big lawn

Calculate how long you need to water your lawn each week by dividing your lawn’s weekly watering needs by the hourly output of your sprinkler. The number you get is your weekly watering duration. 

For example, if your Bermudagrass requires one inch of water per week and your sprinkler puts out 1 ½ inches of water per hour, you should run the sprinklers for ⅔ hour or 40 minutes

You should leave sprinkler on new turf longer than on already established grass. Grass seeds and young seedlings need more water to grow strong roots. But once they mature and become more immune, they don’t need any special treatment.

Decide How Often You Want To Water Your Lawn

An infographic about soil types

Now that you know how long you should run your sprinkler every week, you should decide how often you want to water your lawn based on your soil type

Putting out all the water in one day is not a good idea. If you run your sprinkler for 40 minutes straight, you will end up creating a breeding ground for rot, fungus, and pests. And, if your soil absorbs water slowly, it will end up running off onto the street. What a waste! 

But watering your lawn every day, little by little, is not desired either. You will end up watering only the top layer of the soil. If the water doesn’t reach the grass roots, your lawn will slowly start to brown

To grow a healthy lawn, you should establish a watering schedule that caters to your soil type. Clay and loamy ground holds water longer but absorbs it slower. This type of soil needs to be watered up to three times a week

Sandy soil soaks up water faster but doesn’t hold on to it for long. This soil needs to be watered two to four times a week

Divide the total weekly watering time by the watering frequency to determine how long you need to run your sprinklers. If you need to water your grass for 40 minutes in total and you decide to water your lawn two times a week, you should let your sprinklers run 20 minutes each watering session

Space your watering sessions at least two days apart to let the water penetrate the soil and allow the grass to absorb it. 

Adjust Watering Based On The Weather

A close up shot of a rain gauge

Now that you have all the basics down, you can start adjusting your watering schedule according to the weather. Rainfall will naturally lower your lawn’s weekly watering needs. If you are getting a lot of rain in the week, you may not even need to turn on the sprinklers. 

To avoid overwatering your lawn, track how many inches of rain you are getting and subtract the amount from your weekly watering needs. You can use a rain gauge to measure the rainfall in inches. 

If your lawn needs one inch of water per week and you get ½ inch of rain, you only need to put out ½ inch to meet the weekly quota. Now that you know your new weekly watering requirement, you can calculate the sprinkler run time and weekly watering frequency as you did before. 

On the opposite end, if you are getting a lot of sun and hardly any rain, you should increase your watering. Heat will cause water to evaporate from the soil quicker than usual. Make up for the lost moisture by watering your lawn longer and more often

Water Early In The Morning

A picture of a golf course in the morning with water sprinklers spraying water across it
Image credit:

Running sprinklers in the middle of the day is not recommended. The water will evaporate in the air before it hits the ground. 

Watering grass at night is not the best idea either. Letting the lawn sit wet all night can lead to the growth of fungal diseases.

The best time a day to water your lawn is early in the morning, between 6 a.m. and 10 a.m. Less evaporation occurs at this time than and the winds typically aren’t as high.  

You should also avoid watering your lawn in high winds. The wind will blow dispersed water away from the targeted area, leaving your lawn empty-handed. 

The EPA reports that about half of the water used for lawn care goes to waste because of evaporation, high wind, and runoff. By watering early in the morning, you will use your resources to the maximum. 

Click here to find out more on the best time a day to mow a lawn


What is the best time to water your lawn?

The best time to water your lawn is early in the morning, from 6 a.m. to 10 a.m. Less evaporation occurs in the morning than in the middle of the day. Your lawn will have plenty of time to absorb water before temperatures rise

Is it bad to run sprinklers during the day?

Running sprinklers during the day is not the best idea because the heat will evaporate the water before it hits the ground. The best time to water your lawn is in the early morning. Late afternoon is your second best option.

Get To Know Your Lawn First 

That’s it! Now you know how long to leave sprinkler on! 

The key to growing a healthy lawn is knowing the watering preferences of your grass type. Once you get the basics down, you can develop a reliable watering schedule that you can adapt to your current weather at any time. Use a flow timer to ensure your watering stays consistent! 

Here is what you need to do:

  1. Identify your grass and its watering needs
  2. Calculate the water output of your sprinkler
  3. Calculate how long to leave the sprinkler on per week 
  4. Decide how often you will water your lawn per week
  5. Look out for the rain and heat
  6. Water early in the morning

How do you water your lawn? Let me know in the comments below, and feel free to ask questions. 

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About The Author

Nadya Jones

Nadya is a writer, entrepreneur, and designer based in Raleigh. She writes in her blog, the one you are visiting right now, where she shares her love for landscaping, gardening, and outdoor design. Her husband Brett provides her with a lot of inspiration and behind-the-scenes content. Together, they work on creating beautiful outdoor spaces that serve as an extension of their home and inspire others to do the same. If you are interested in landscaping, gardening, or outdoor design, be sure to check out the blog! Also, follow Nadya on Twitter, Instagram, Pinterest, and Flickr!

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