How To Determine Sprinkler Heads Per Zone For Optimal Residential Irrigation

Kenneth Wilson

Determining the right amount of sprinkler heads per zone can either make or break your dreams of having a lush lawn. Sprinklers keep your garden consistently and adequately watered. It's a must for homeowners to follow proper yard and garden care.

That's why it's essential to figure out just the correct number of sprinkler heads you need– which boils down to two things: pounds per square inch (PSI) and the gallons per minute (GPM). Keep in mind that the sprinkler head consumes different water quantities. Hence, it's best to calculate how many sprinklers you can use in a zone or valve.

Residential Sprinkler System Average Costs

On average, a standard two-zone system (with three heads in each zone) runs for $1,200 to $1,500. Note that this ballpark figure doesn’t include professional labor rates, though. Accordingly, the required sprinkler heads will vary from one property to another.

How Many Sprinkler Heads do You Need per Zone?

The thing is, there's no magic value that determines the exact number of sprinkler heads you can install on a given zone or valve. It will vary on a case-to-case basis, depending on your flow rate and the water supply pressure in your property.

Other factors may influence the result. For instance, some sprinkler head brands have unique specifications, affecting your overall calculations. That said, you may want to stick with one brand to make the calculations a bit easier. (Related: 7 Types of Sprinkler Heads (Pros, Cons & Everything You Need to Know))

Now, let's discuss two critical concepts in calculating the number of sprinkler heads you need: PSI and GPM.

Pounds Per Square Inch (PSI)

Determining your home's water system pressure doesn't have to be too complicated, but it will need some special equipment. You will need to attach a pressure gauge to an outside faucet situated closest to the water meter, for starters.

Important note: Ensure to turn off any faucet (or anything else) inside your home that uses water before doing this step.

Afterward, you may record the gauge reading, ideally in pounds per square inch. You may also contact your water company to tell you the compatible sprinkler heads for your current water supply. Remember that you shouldn't use a sprinkler head with a lower or higher PSI range than your current water system.

Gallons Per Minute

Another critical concept to understand is the irrigation system's flow rate, commonly measured in gallons per minute. The good news is– you can measure the GPM by yourself easily. Get a bucket with a standard size (1 gallon or 5-gallons), put it under the outside faucet before turning it on.

(As previously mentioned, ensure that anything that uses water both inside and outside of your home is shut off.) Then, measure how long it typically takes for the bucket to be filled up in seconds. Calculate the average flow rate by:

  • Multiplying the bucket size by 60
  • Dividing it by the total time in seconds

Let's say it took 20 seconds to fill your 5-gallon bucket. 5 x 60/20 will give you 15 GPM.

How Do You Calculate Zones?

With the two significant calculations, there's another step you need to determine before coming up with a certain number of sprinklers that need to go in each zone– how many sprinkler heads you need overall.

You can start by mapping your current yard. This allows you to determine the location where sprinklers are needed based on the distance and the direction of their spray patterns. In each zone, you need to sort out every plant or the particular lawn areas that need watering. Opt to jot it down somewhere as they are pieces of important information.

Once that's taken care of, add the flow rate in GPM for every sprinkler head before dividing it by your home's water supply GPM. Ultimately, the number will indicate the total zones that you need.

Suppose each sprinkler needs a 1.5 GPM rate, and you have about 20 pieces. This means you need 30 GPM overall. If your current sprinkler system can only handle 16, you must delegate two zones to cover the area adequately.

Note: Some homeowners commonly take this information with a grain of salt, given that it's not an exact science. You are always free to make any necessary adjustments you deem fit.

Let's say one or two sprinklers are weaker or have shorter spraying distances than you initially anticipated– this may suggest you have too many heads in a single zone.

Expert-Backed Sprinkler Head Per Zone Tips

Keep in mind that every zone in the sprinkler system runs all heads simultaneously. So if you have too many, the pressure in each one will decrease– as the system cannot be controlled head by head. (If you find yourself in this situation, you may want to try removing one head to see if it helps.)

Local experts recommend listing down all the factors to consider in laying out your sprinkler systems– such as the water flow and pressure, slope of the ground, plant types, sprinkler head types, the shape and total size of the area that needs to be covered.

You will need to position your sprayers properly, depending on whether the lawn is narrow, irregularly shaped, or rectangular. Also, you may want to consider using rotors than sprinkler heads– as these offer better coverage for large areas.

Frequently Asked Questions (FAQs)

What are PSI and GPM?

Pounds per square inch, aka “PSI,” is the measurement used to determine water pressure. Water pressure varies from home to home, so it is crucial to know your home’s pressure before you purchase a new sprinkler. Meanwhile, gallons per minute or “GPM” measure flow rate. It is how fast the water is distributed from your pump or spigot through the house going to your sprinkler.

What can I do if the water sprays too weakly from the sprinklers?

There are situations where the sprinkler runs weaker and on a shorter distance compared to what the manufacturer told you. It is a good indication that too many sprinkler heads are in a single zone. One of the things you can do when experiencing poor performance is to remove one of the heads. This way, you can avoid combining the sprinklers with different flow rates. Various sprinklers need different amounts of water at the same time, making it more difficult to estimate how many zones and heads you'll need each zone.

How often should I water the lawn?

Unfortunately, there are several misbeliefs online on how you must be watering your lawn. Many guides say daily watering is ideal, but it may only prevent the grass from entirely drying out or flooding the grass bed. The same applies when it comes to watering your lawn during the nighttime. It's crucial to ensure correct evaporation to avoid pathogens from saturating the grass. If not, it may only leave long-term damage to your grass and leave you several issues such as shallow roots. Ideally, water your lawn at least two to three times a week. Watering the grass every few days gives it ample time to evaporate properly. The soil moist needs to be around 5 to 6 inches deep, and daily watering may only lead to shallow roots, which is a cause of additional stress on your grass.

Kenneth Wilson
February 12, 2022
Contractor Tips, Yard & Garden

Kenneth Wilson

Retired contractor. Currently residing in Southwest Florida. Now in semi-retirement, I write and manage this blog focused on helping home owners make savvy decisions when it comes to finding contractors and getting their projects done. I also operate remodeling design service for homeowners.

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