How to Spot Irrigation Coverage Gaps

Coverage gaps are overlap failures, not “dry soil”

Most sprinkler patterns are designed to work through overlap, meaning each head is expected to contribute part of the final dose while neighboring heads fill in the rest. A coverage gap forms when that overlap does not happen, so the area receives a partial dose every time the zone runs even though the system looks active and the yard sounds like it is being watered.

The gap is not random, and it usually repeats in the same shape because it is caused by fixed hardware and fixed spacing.

Stress appears first where the lawn has the least margin

Coverage gaps rarely announce themselves immediately because grass can coast on stored moisture and shallow surface wetness for a short period.

The weakness shows up when demand rises and the root zone needs a full recharge to stay stable, which is why new lawns often reveal gaps quickly since they operate with a smaller buffer, similar to the vulnerability described in How Long New Grass Needs Extra Water.

Visible contrast after watering is an important clue

When watering ends, some sections darken evenly while others stay lighter or shift back toward dry appearance sooner.

If the same areas repeatedly fail to hold that post-watering darkening, it often means the surface is getting misted but the dose is not building depth, which turns the “wet look” into a false signal.

Recurring patterns point to distribution, not weather

If a lawn struggles in the same spots across different weeks and different seasons, the system is leaving those sections behind on a regular schedule.

This is one reason water problems feel seasonal or cyclical even when the homeowner changes run times, which fits the repeat behavior described in Why Water Problems Reappear Each Year.

Run time changes can make gaps easier to notice

When run times increase, well-covered areas often look overly wet while under-covered areas still look stressed.

That split is a hallmark of a coverage gap because the system is applying extra water everywhere, but only the properly overlapped zones receive the full benefit while the gap remains under-dosed.

Soil feel can be misleading in gap zones

Many coverage gaps still get enough water to soften the top layer.

That can trick you into thinking water is reaching roots when it is only wetting the surface, which is why correct diagnosis depends on separating surface wetness from root-zone support, as explained in How to Diagnose Water Issues Correctly.

Edges and corners are common failure points

Perimeters often depend on a single head’s reach or a partial arc.

When that head underperforms, or when wind and pressure changes shorten its throw, the outer band becomes a chronic low-dose strip even though the rest of the zone looks fine.

Small mechanical differences create large lawn differences

A nozzle that is slightly misaligned, a head that does not rise fully, or a pressure loss that reduces throw distance can remove overlap without making the sprinkler look obviously broken.

The lawn responds as if it is being watered unevenly because it is, and the gap becomes more visible over time as roots retreat from the under-supported area.

Coverage gaps turn watering into a long-term imbalance

When the same area receives a partial dose for weeks, it develops shallower roots and a faster stress cycle than the rest of the yard.

That difference makes future recovery harder because the gap zone becomes the first place to fail and the last place to rebound, even if everything else looks healthy.