Why is my new sprinkler system not reaching parts of the lawn?

Start by watching each zone run

Sprinklers that miss part of a lawn are usually a spacing, aim or nozzle problem, not a sign the whole system is broken. The fastest way to find which is to watch it work. Rain Bird, the manufacturer, suggests you start by activating one zone or program at a time on your controller^[2] and walk around to see how each head waters. Most controllers have a manual run function for this, and app-based ones do it from your phone.

Put a flag in the ground at every dry or brown patch, then match each one to the head that should be covering it. That tells you whether you have one bad head or a layout that never reached the spot.

The usual causes

Heads too far apart. EPA's WaterSense program gives the test: Each sprinkler should be able to reach the sprinkler head next to it, known as head-to-head coverage.^[1] If a spray stops short of the next head, you get a dry band between them. Aim matters too: Make sure to properly direct sprinkler for uniform coverage to avoid dry spots in the landscape.^[1]

Heads that do not pop up, or are tilted. WaterSense tells owners to Look for heads that do not pop up fully or are tilted as they can unexpectedly spray to the wrong areas.^[1] A head that settled, got buried under new sod or was knocked by a mower can throw water at the sky or the sidewalk instead of the grass.

Spray landing on hardscape. Water on pavement runs to the storm drain, not the lawn. Extension's advice is plain: Water the lawn — not driveways, sidewalks, or roads — by adjusting sprinkler heads.^[3]

Misting from high pressure. A fine fog drifts in the wind and never reaches the far edge. WaterSense says to Avoid overspraying or misting due to high pressure.^[1] and suggests it: Consider installing spray sprinkler bodies with integral pressure regulation which maintain consistent water pressure so that nozzles can operate efficiently.^[1]

The wrong or clogged nozzle. A nozzle with the wrong arc or throw distance leaves gaps, and a plugged one under-sprays. Swapping one is a small job: Remove the old nozzle and filter screen.^[2] Then fit a new screen and a nozzle with the right pattern and throw distance.

Too many heads on one zone. If a zone was designed with more heads than the water supply can feed, the far ones weaken. That is a design fault, so it is the installer's to correct, not something to patch with new nozzles.

Measure it with a catch-can test

If the cause is not obvious, measure. Virginia Cooperative Extension describes the audit as placing at least five broad, wide-mouthed containers at distances of approximately 20, 40, 60, 80, and 100 percent of the maximum throw of the sprinkler(s)^[3]. Run one zone for a set time and compare how much water each container collects. Extension's reason for doing it: it will help to diagnose and prevent either dry or saturated areas that can lead to an unhealthy turf^[3]. It also gives you numbers to show the installer.

Run time can look like a coverage problem on a new lawn. Extension notes that smaller amounts of water applied every three to four days may be required to allow water to enter the soil without causing runoff^[3]. A spot that stays dry in one zone but soggy next to it often means two zones overlap badly.

What you can safely adjust

Run the zone, flag the dry spots, then work head by head. Straighten tilted heads and raise any that sit low, adjust arc and distance with a small flat screwdriver on the top of a spray head, and clean or replace a clogged nozzle and its filter screen. Re-run the zone after each change so you can see whether the flag is still dry.

Leave buried pipe, valves and the backflow assembly alone. Those are the installer's work.

If the system is new, tell the installer in writing

A new system with coverage gaps is a workmanship question, and the installer should hear about it first. DPOR advises: Be sure to address all problems or complaints directly to your contractor in writing, so that you both have a record.^[5] Attach your flag map and catch-can numbers. If the installer does not respond, DPOR says: If the contractor refuses to make corrections, you should file a written complaint with the Board for Contractors^[5].

Stop and call a pro if

• Water pools on the lawn between cycles. WaterSense says: Between irrigation cycles, look for areas of the landscape with water pooling on the surface; that could be a sign of an underground leak.^[1]
• A whole zone is weak or will not run. That points to a valve, buried pipe or the water supply, not a nozzle.
• Joints at the heads leak. Leaking joints can also be a sign of too much water pressure or particles in the water.^[1]
• The fix means cutting into the line or opening the backflow assembly. Both belong to a licensed contractor.
• The installer will not return. Use the written complaint route above.

Getting help in Virginia

EPA's WaterSense program lists what a certified irrigation professional does, including Audit: Test your irrigation system to ensure it performs efficiently.^[4] It also says to start by confirming that the contractor is licensed and bonded, then ask for training and professional certifications^[4]. For the layout and permit side, read what installing an in-ground system involves, what a system costs in Virginia and whether you need a permit or backflow preventer. More in irrigation answers and irrigation businesses.

When you are ready, describe the coverage problem once and licensed local contractors can quote it.