How Long to Run Lawn Sprinklers – Solved

Although not all homes need a lawn sprinkler, it is necessary for many homeowners. However, it is one thing to purchase a lawn sprinkler, it is another to understand how long and often to use it. Several factors can affect how long you should run your lawn sprinkler, including the climate and size of the lawn. It is crucial to get these things right or you can do damage to your lawn.

How Much Water Does a Lawn Need?

How much water a lawn need depends on several factors, including the climate, type of grass, soil type, and time of year. However, the average lawn in the United States requires one to one and a half inches of water per week to stay healthy. Less than that, and you run the risk of your grass dying. More than the prescribed amount, and the grass could become waterlogged leading to lawn damage.

Since you do not want to risk ruining your lawn by over or under-watering it, it is best to determine how much water it needs before starting your sprinklers. Fortunately, there are a few simple actions you can take to determine how much water your lawn requires. 

Check the Soil -There is no substitute for testing the soil. Push a screwdriver or another similar tool into the ground to test for moisture levels. If it enters easily, the soil is moist enough and does not need immediate watering. However, if it is challenging to push it in, and your feel resistance, then the soil is dry and needs water.

Monitor Your Lawn – Check your lawn periodically to see if it starts turning yellow or brown, or wilting at the tips. Color changes or wilting is a definite sign your grass more frequent watering. 

Use a Rain Gauge – Another option is to use a rain gauge. A rain gauge will measure how much water your lawn gets from rainfall. You can measure the rain weekly or fortnightly to reduce variance from high or low rain periods. Once you know how much rainwater your lawn receives, you can adjust how much additional irrigation it needs.

Adjust for Weather – You will need to adjust how much water your lawn receives based on the weather. Your climate has a significant impact on how much water lawns need. Lawns typically need more water in hot, humid, or dry climates, or during periods of high winds, which can draw moisture from the soil surface. In these circumstances, it’s always best to go back to the standard soil moisture test and push a stick or other implement into the soil to test its structure and moisture level.

Testing soil moisture levels
Testing soil moisture level

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Variables Affecting Water Requirements

The volume of water a lawn needs is affected by several variables, including weather, soil, and grass type and as a result, it is challenging to give a one size fits all answer to how long to run a lawn sprinkler. Let’s work through each variable and understand how it affects irrigation needs and understand how to account for it in your irrigation planning.

Grass Type

Cool-season grasses such as Kentucky bluegrass and fescue may require more frequent watering during dry periods than warm-season grasses such as Bermuda and Zoysia, both of which are drought tolerant and require less water. 

Centipede grass, while not as popular as some other types of grass, is another great choice for areas with hot temperatures and low rainfall because it has good natural drought resistance. It can go longer periods between waterings without showing signs of stress.

Soil Type

Another factor to consider is the type of soil in your lawn. Different types of soil retain water better than others. As a result, lawns with those types of soil need less watering than others. Conversely, some types of soil drain water quickly and need more frequent watering. For example, sandy soil drains water quickly, forcing homeowners to water their lawns more often than those grown in clay soil.

Understanding your soil type is important in allowing you to work out the most appropriate watering schedule. Your soil type will also help you improve your general lawn care routines. Clay soils tend to be higher in nutrients and require less feralization, whereas sandy soil is typically poor and may require a specific grass type in order to create a lush lawn. 

Prevailing Weather Conditions

A major factor that affects how long to run sprinklers is more than any other is the prevailing weather. It won’t come as a surprise to you that your local prevailing weather conditions have a tremendous effect on lawn health. If you live in an area with high rainfall, you will not need to run your sprinklers often, and of course, the opposite can be said for areas of low rainfall and high levels of sun

Irregular weather is also a consideration. You cannot simply water 1 inch of soil per week and close the back door on your lawn. During the warmer period of weather, you need to be prepared to increase the watering schedule. Infrequent, deep watering is far better than regularly spraying the lawn with a drop of water. The goal is to soak the soil deep down into the lawn roots and get past the surface soil. 

Regardless of where you live, your lawn will need more water during the summer than in the winter due to the higher temperatures and increased hours of sunshine. In cold environments, you will most likely find that your lawn will not require any additional water, whilst the grass goes dormant when temperatures drop below 40F.

Dormant Lawns

The last significant factor that can affect how much water grass needs is whether it is dormant. Lawn dormancy occurs when grass reduces its growth and water usage in response to environmental stress, such as drought or extremely cold temperatures. 

During dormancy, the grass may simply stop growing or with certain grass types, it can turn brown or yellow and appear dead. However, it is actually conserving energy and resources to survive until conditions become more favorable for growth. In the winter, when it snows, grass enters dormancy and does not need watering.

Dormancy is a natural survival mechanism for grass, and it can help the lawn recover more quickly when conditions improve. However, it is crucial to note that a dormant lawn still needs water to survive. So, you should provide your lawn with at least an inch of water each week during prolonged periods of drought or heat to prevent permanent damage to the grass.

You do not need to worry about watering your grass during winter unless there is no rain at all.

Establishing How Long to Run Sprinklers

Now that you understand the factors affecting how much water grass needs, you must establish how long to run sprinklers. There are several factors to consider, like the flow rate of the sprinkler, its run time, and the area of the lawn being irrigated. You can also use the simple tuna can method to help determine how much water is landing on a surface area over a given timeframe, I will talk further about this method shortly.

Flow Rate

One of the most important factors to consider when running your sprinklers is the water flow rate. Without knowing the flow rate of your sprinklers, you can not accurately assess how long to run them. Or as is often the case, how much to adjust them if the current schedule is not working out for you.

Many sprinkler systems will provide users with information on how much water precipitates over a set period. However, if you do not have this information, there are things you can do, such as install an inline flow meter or manually measure water flow using the Simple Tuna Can Method, which I will cover shortly.

Area of Lawn Being Irrigated

Another thing to consider is the area of your lawn is irrigated. Lawns with larger surface areas need more water than smaller lawns because there is more space for water to evaporate. Additionally, since water is going to a larger surface area, it takes longer to water the entire lawn. As a result, you will need to lengthen the amount of time you leave your sprinklers on. It is also possible that you will need to purchase more than one sprinkler for large lawns.

Think of it like this… if your available water flow rate is hitting a section of lawn 1 ft sq., it will very quickly saturate the soil below the 1-inch level that we are aiming for. If the same available water flow rate is being turned into a spray or mist and is covering 10 ft sq. the time required to saturate 1 inch of soil will be a minimum of 10 times longer. As the surface area is 10x the size, plus you will lose moisture to wind and evaporation as the water is distributed.

Run Time

If you know the flow rate, and lawn size you can then, in theory, calculate how long to run your sprinkler. There are two schools of thought here:

  1. Know your system flow rate, understand the areas being covered, and multiply that by a time scale, and then you will get the answer to how much water you are delivering to your lawn. 
  2. Perform a simple yet practical test using the Simple Tuna Can Method. Which, I think is far easier and therefore better suited for most homeowners. So let’s talk about this in more detail.

Use the Simple Tuna Can Method

The simple tuna can method is a technique for measuring how much water your lawn is receiving from your sprinkler system. It involves placing empty tuna cans (or any other shallow, straight-sided container) around your lawn while your sprinkler system is on and measuring the depth of the water collected in the cans after a set period. You can time how long it takes for the tuna can to fill up, which is roughly an inch of water, perfect!

Here are the steps for the simple tuna can method:

  1. Place several empty tuna cans around your lawn at various distances from your sprinklers. Place them on level ground and avoid areas with excessive shade and wind.
  2. Turn on your sprinkler system and let it run for a set period, starting with 20 mins.
  3. Turn off your sprinkler system and immediately measure the water depth in each tuna can using a ruler or measuring tape. Record the measurements for each can. 
  4. Calculate the average depth of the water in the tuna cans. Doing so will give you an idea of how much water your lawn is receiving from your sprinkler system.

If you run into any complications working out how long you need to run your sprinkler to achieve 1-inch of irrigation, you can simply time how long it takes for the tuna cans to completely fill. This is the time you need to deliver 1 inch of water to your lawn.

By using this method, you can determine if your lawn is receiving the appropriate amount of water from your sprinkler system and adjust accordingly. This method is a simple and inexpensive way to measure water depth and is commonly sued by homeowners, gardeners, and landscapers.

How Often to Run Sprinklers

Everyone needs to run their sprinklers for different amounts of time. If you live in a hot or dry climate, you should consider watering it once every two to three days. Conversely, cooler, wetter climates only need watering once a week. 

Best Time to Run Sprinklers

It is crucial to note that it is best to water your lawn early in the morning before the weather gets too hot. It is cooler during these times, so there is less evaporation and the vast majority of the water will be able to soak deep into the soil and not evaporate.

You will hear people advising to water in the evening, again, due to the cooler, temperature. But this is not recommended, as the moisture on your lawn overnight can encourage fungal disease leading to a number of lawn care problems. 

Other Considerations

Before we wrap up, I want to cover a few more things you should consider before determining a set amount of time to run your lawn sprinklers.

Dry or Wet Patches During Watering

If you notice dry or wet patches while watering your lawn, it is a sign of uneven water distribution from your sprinkler system. Uneven water distribution can be caused by your sprinkler head placement, the system’s water pressure, the design of your irrigation system, soil type, and weather conditions.

Steep Lawn Gradient

A steep lawn gradient can cause problems when watering your lawn with a lawn sprinkler. It can lead to uneven watering because sprinklers are designed to water evenly over flat surfaces. On steep slopes, water will run off to the bottom. Furthermore, it can cause soil erosion and result in water waste.

Verdict: How Long to Run Lawn Sprinklers

It depends…well sorry, it does. It depends on the flow rate of your sprinkler, the area being covered by the jet or spray of water as well as a number of other environmental factors such as grass and soil type as well as weather conditions.

The easiest way to determine how long to run your lawn sprinklers is to use the Simple Tuna Can Method. Use empty tuna cans located around your lawn, and time how long it takes for you to collect 1-inch of water from your sprinkler set up.