Why Do Sprinklers Leave Dry Spots in a Lawn?

As an Amazon Associate we earn from qualifying purchases.

Dry spots in a lawn that is watered by sprinklers are a question of coverage. The question why do sprinklers leave dry spots in a lawn has a mechanical answer: water from each head does not land evenly across the turf, so some areas get less than others. Colorado State University Extension and Utah State University Extension both describe the causes in practical terms. This article follows their descriptions, explains how each cause produces a dry patch, and notes where the sources stop.

Quick answer

Heads placed too far apart, or outside a square or triangle pattern, leave gaps that uniform coverage never fills.
Tilted, sunken or buried heads throw water unevenly, and a few degrees of tilt can cause dry spots.
Clogged nozzles, broken rotors, low pressure and mixed heads reduce the water that reaches part of the lawn.

How we chose

Two university extension publications were used, both reachable at the time of the check. Commercial irrigation vendor pages were not used for any claim in this article.

How head spacing creates gaps

Colorado State University Extension says that “Dry spots may be caused by poor coverage if irrigation heads have been installed too far apart or not in a recommended square or triangle pattern.” It adds that “Where sprinkler heads are located far apart, uniform water coverage will never be achieved.” Those two statements point to spacing as the first thing to check.

The overlap between neighboring heads is what fills the gaps. Utah State University Extension asks homeowners to “Check to see if you have head-to-head coverage between sprinklers.” Colorado State gives the same idea as a rule: “the spray from one head should extend to touch the next spray head.” Head-to-head coverage means each head reaches its neighbor, so the water from both overlaps in between.

Colorado State also ties placement to the pattern: heads should be positioned “in square or triangle patterns to achieve the overlap recommended by the manufacturer.” When a layout does not follow that pattern, the overlap can disappear in some places while remaining in others.

Utah State gives a direct path for a system that lacks overlap: “If necessary, consult a qualified professional to design a system with head-to-head spacing.”

Mixed heads and precipitation rates

Head type matters as much as position. Colorado State says that “All heads on a zone should be of the same type with the same manufacturer’s precipitation rate (amount of water sprayed in inches per hour).” It also states that “If heads are mixed, the landscape receives too much water in one area and too little water in other areas.” That is a direct mechanism: when two types with different output share a zone, one part of the lawn gets more water and another gets less.

Utah State makes the same point from a different angle: “Different nozzles have different precipitation rates which cause problems in the landscape.” Its maintenance advice is to “Make sure each irrigation zone has the same type of nozzles.” Colorado State adds a related rule: “Do not install rotors and spray heads on the same zone.”

Colorado State also gives a rate comparison: “rotor heads (Figure 5) release 1/3 the amount of water of spray heads (Figure 6) in the same run time.” Rotor and spray heads on one zone therefore put out very different amounts of water in the same run time.

Tilted, sunken and buried heads

Tilt is one of the most common causes. Colorado State explains that “Tilted heads warp the spray pattern, throwing more water to one side and less to the opposite one.” It adds that “Tilted heads cause dry spots in the landscape and are very common due to strikes from mowers and foot traffic.” Utah State puts the effect into scale: “Tilted sprinkler head – A few degrees of tilt can cause dry spots in the lawn.” Its description of tilted heads also says that “Tilted heads can cause ponding and uneven coverage.”

Height matters too. Utah State describes sunken heads this way: “Sunken heads do not rise high enough to spray beyond the lawn surrounding the sprinkler.” It notes that “Some sprinkler heads may be tilted (Figure 6), surrounded by grass, or even buried.”

Utah State also links the problem to pressure: “In addition to wasting water, this will have a negative impact on water pressure, causing dry spots in the lawn.” Colorado State’s checklist asks whether “any nozzles or irrigation heads [are] buried by surrounding grass or other plant growth.” Both sources treat burial as a coverage problem, not only an appearance problem.

The fixes the sources describe are mechanical. Colorado State advises to “Twist to raise or dig out and reposition heads on flexible risers (swing pipe) or add a threaded riser to raise heads on inflexible risers to grade level.” Utah State recommends to “Raise sunken heads to grade or replace existing short pop-up heads in the lawn with taller pop-ups, as necessary.” Adjusting the head angle is also in the scope of the sources: Colorado State says to “Adjust sprinkler heads to be perpendicular to the soil surface.”

Clogged nozzles, broken rotors and pressure

Blocked or damaged parts reduce the water that a head throws. Colorado State states that “Clogged nozzles or broken rotors also cause dry spots.” Utah State describes a broken head with a missing or damaged nozzle, where “The sprinkler nozzle may be missing or broken off.” Colorado State also notes that “Nozzles may also wear with time warping spray patterns.”

Pressure works in both directions. Colorado State explains that “Low pressure causes large droplets of water that fall short of the intended area.” It lists other causes: “low system water pressure, a plugged nozzle, failing rotor, or a south, west or windy exposure.” Pressure that is too high creates a different problem, since “Over-pressurized heads emit a mist that blows away, wasting water.” Utah State tells readers to “Look for a very fine mist from spray heads caused by excessive pressure in the system.” The source fix for high pressure is “an in-line pressure regulator for areas with high water pressure,” which Colorado State recommends directly.

Colorado State also tells readers to “Operate systems under the recommended pressure to avoid misting.” Pressure that is off the recommended level is therefore a reason to check the system before blaming the spacing alone.

Measuring coverage and checking the system

Utah State advises that “Turn on each irrigation zone monthly and look for sunken, broken, tilted (Figures 3–6) or clogged heads and make necessary repairs.” It also says to “Check to see if the sprinklers are covering the desired area uniformly.” Colorado State asks whether “there are heads that spray a hard surface or that leave part of the landscape without water.”

Colorado State gives a way to measure the water instead of guessing: “Place four identical, straight-sided cans between irrigation heads in a zone.” The same source suggests that if you are “unsure or need to confirm the manufacturer’s ratings of how much water spray heads deliver per hour (precipitation rate), follow these steps.”

The sources list sunken, broken, tilted and clogged heads as separate faults, and each has its own fix in the text above.

What we could not verify

What the sources do not say

This article does not give a spacing distance for a general lawn, because the two sources reviewed describe placement by overlap and pattern rather than by a single number. Neither source gives a single pressure value that applies to every system, and both point to the manufacturer’s recommended pressure instead. The sources also do not give a schedule for when heads should be inspected beyond the monthly zone check that Utah State describes.

The sources reviewed are extension publications, and their advice is written for general home systems. Any system with unusual layout, slope or water supply may need the design help that Utah State recommends.

Frequently asked questions

Why do sprinklers leave dry spots even when they run?

Can a tilted sprinkler head cause a dry spot?

Yes, according to Utah State University Extension, which states that “Tilted sprinkler head – A few degrees of tilt can cause dry spots in the lawn.”

What does head-to-head coverage mean?

Colorado State describes it through the rule that “the spray from one head should extend to touch the next spray head.” Utah State uses the same term when it asks homeowners to “Check to see if you have head-to-head coverage between sprinklers.”

Can low water pressure cause dry spots?

Colorado State says that “Low pressure causes large droplets of water that fall short of the intended area.” It lists “low system water pressure” among the other causes of dry spots.

How can I find the heads that cause dry spots?

Utah State advises to “Turn on each irrigation zone monthly and look for sunken, broken, tilted (Figures 3–6) or clogged heads and make necessary repairs.” Colorado State suggests placing “four identical, straight-sided cans between irrigation heads in a zone” to measure the water.

For related soil basics, see how to make garden soil better and how to fertilize vegetables.

Sources

Colorado State University Extension, “Operating and Maintaining a Home Irrigation System,” https://extension.colostate.edu/resource/operating-and-maintaining-a-home-irrigation-system/ (opened 2026-10-27)
Utah State University Extension, “Irrigation System Maintenance,” https://extension.usu.edu/yardandgarden/research/irrigation-system-maintenance (opened 2026-10-27)