Sprinkler System Troubleshooting Guide

Most sprinkler system problems come down to one of four places: the controller (programming, power or a bad station output), the zone valve (solenoid, diaphragm or debris), the pipe (a break or leak) or the heads themselves (clogged nozzles, broken risers, misaligned spray). Work from the controller outward. If no zones run, start at the controller and backflow device. If one zone will not turn on or will not shut off, the valve is the usual suspect. If pressure is low or water is bubbling up in the lawn, look for a broken pipe or head. This guide walks through each symptom with the checks that solve the majority of residential problems.

In this guide

1. Quick Diagnosis Table
2. Problem 1: No Zones Turn On
3. Problem 2: One Zone Will Not Turn On
4. Problem 3: A Zone Will Not Shut Off
5. Problem 4: Low Water Pressure
6. Problem 5: Geysers, Leaks and Soggy Spots
7. Problem 6: Heads Not Popping Up or Spraying Wrong
8. Problem 7: Dry Patches Despite Watering
9. Tools Worth Having
10. When to Call an Irrigation Pro
11. Frequently Asked Questions

Quick Diagnosis Table

Symptom	Most likely cause	First check
No zones turn on	Controller, power, rain sensor, closed main or backflow valve	Run a manual zone; check sensor bypass and valves
One zone will not turn on	Solenoid, wire, valve or controller station	Manually open the valve at the bleed screw
Zone will not shut off	Debris in valve, torn diaphragm, stuck solenoid	Unplug controller; if still running, it is the valve
Low pressure, one zone	Broken pipe or head, flow control closed, too many heads	Walk the zone while it runs
Low pressure, all zones	Main valve partly closed, backflow problem, municipal pressure	Check valves at the point of connection
Geyser or bubbling	Broken head, riser or pipe	Flag the spot and dig
Soggy area when system is off	Leaking valve or low-head drainage	Check valve weeping and lowest heads
Heads do not pop up	Low pressure, dirt around head, stuck wiper seal	Clean around head and flush
Dry patches	Coverage gaps, blocked or misaligned heads	Catch-cup test and adjustment

Problem 1: No Zones Turn On

When the whole system is dead, the cause is almost always upstream of the individual valves.

1. Check the controller display. Blank screen means no power: check the outlet, GFCI, breaker and the transformer plug. A display reading “off,” “rain delay” or “sensor active” means the controller is deliberately not watering.
2. Bypass the rain sensor. Most controllers have a sensor bypass switch or setting. A stuck or wet sensor will block every zone.
3. Run a manual cycle. If zones run manually but not automatically, the issue is programming: check date, time, AM/PM, start times and watering days. Our guide on setting a sprinkler timer walks through programs.
4. Check the water supply. Make sure the main irrigation shutoff is fully open and the backflow preventer’s handles are open (parallel to the pipe on most ball valves). After winter, these are often left closed. See our spring sprinkler startup guide.
5. Check the master valve or pump start relay. Systems with a master valve or well pump will not run any zone if that component fails.

Problem 2: One Zone Will Not Turn On

If other zones work, the problem is specific to that zone’s valve, wire or controller station.

Step 1: Open the valve manually

Find the valve box (usually a green lid near the water source or in a bed). Open the zone by turning the bleed screw a turn or two, or by turning the solenoid a quarter turn counterclockwise. If water flows to the heads, the valve body and pipes are fine and the problem is electrical. If nothing flows, the valve is clogged or damaged, or the supply is shut off.

Step 2: Test the solenoid and wiring

• At the controller, set a multimeter to ohms and measure between the zone terminal and the common terminal. Most residential solenoids read roughly 20 to 60 ohms. A reading near zero suggests a short; an open (infinite) reading suggests a broken wire or a failed solenoid.
• Repeat the test at the valve directly across the solenoid leads. If the solenoid tests good at the valve but bad at the controller, the wire between them is damaged, often by digging or a corroded splice.
• With the zone running, measure voltage at the controller terminals; most systems supply about 24 to 28 volts AC. No voltage on one station suggests a failed controller output; move that zone wire to a spare station to confirm.

Replace a bad solenoid by shutting off water, unscrewing the old one and threading on a compatible replacement. Use waterproof grease-filled connectors on all splices; ordinary wire nuts corrode underground.

Problem 3: A Zone Will Not Shut Off

Unplug the controller or turn it to off. If water stops, the controller is sending a signal (check for overlapping programs or a failed station). If water keeps running, the valve is stuck open.

1. Make sure the bleed screw and solenoid are fully closed.
2. Shut off the main irrigation supply.
3. Remove the valve bonnet screws and lift the bonnet. Inspect the diaphragm for tears and the small ports for grit, sand or pipe-thread tape.
4. Rinse the diaphragm and clean the ports with a pin. Briefly flush the valve by turning water on with the bonnet off (stand aside).
5. Reassemble with the spring and diaphragm seated correctly. Replace the diaphragm or the whole valve if damaged.

Valves often stick right after a repair elsewhere in the system, because the work flushes debris into them. Flushing lines after any pipe repair prevents this.

Problem 4: Low Water Pressure

Low pressure in one zone

• Walk the zone while it runs. A broken head or riser shows up as a fountain; a broken lateral pipe shows up as bubbling, a soggy depression or a gushing spot.
• Check the flow control on top of the valve (a handle or stem). If someone turned it down, open it fully.
• Count heads. A zone with added heads may exceed the supply’s capacity. Splitting the zone or converting some heads to lower-flow rotary nozzles can help.
• Look for clogged nozzles and filter screens; remove and rinse under a tap.

Low pressure in all zones

• Check that the main shutoff and both backflow test-cock valves are fully open.
• A faulty pressure regulator or a failing backflow device can restrict flow; backflow repairs and testing often require a certified tester depending on local code.
• Check household pressure at an outdoor spigot with a gauge; typical residential pressure falls roughly between 40 and 80 psi. Low supply pressure limits how many heads a zone can run.
• Well systems: check the pump, pressure tank and well recovery.

Problem 5: Geysers, Leaks and Soggy Spots

A geyser means a head or riser snapped, often from a mower or vehicle. Shut off the zone, dig around the head with a hand trowel, unscrew the broken body or riser and replace it with the same make and model so coverage matches.

For a broken PVC pipe, dig a hole large enough to work in (about a foot beyond the break each way), cut out the damaged section and install a slip-fix coupling or a repair coupling with PVC primer and cement. Poly pipe uses barbed insert fittings and stainless clamps. Flush the line before reinstalling heads.

A soggy spot that stays wet when the system is off usually points to a valve that leaks through (weeping), or to “low-head drainage,” where water drains out of the lowest head after each cycle. Check-valves installed in the head or under it solve low-head drainage. Valves that weep need cleaning or a new diaphragm.

Problem 6: Heads Not Popping Up or Spraying Wrong

• Head stuck down: dirt and grass around the cap. Clear it, pull the riser up and flush. Replace if the wiper seal leaks badly.
• Heads barely rise: low pressure for that zone, or a leak elsewhere.
• Misting and fogging: pressure is too high for spray heads; pressure-regulating heads or a regulator fix this.
• Spraying the house or street: adjust arc and radius. Our guide on how to adjust sprinkler heads covers rotors and sprays.
• Tilted heads: dig around, straighten and backfill firmly so the head sits vertical and level with soil.

Problem 7: Dry Patches Despite Watering

Dry spots usually reflect coverage, not runtime. Place several straight-sided cans across the zone, run it for 15 minutes and compare depths. If some cans collect much less, heads are blocked by grass or shrubs, nozzles are mismatched or spacing is too wide. Sprinklers should throw water to the next head (“head-to-head coverage”). Mixing rotors and sprays on the same zone also creates uneven watering, because sprays apply water much faster. If the layout is fundamentally off, our guide on how to plan a sprinkler system explains spacing and zoning.

Tools Worth Having

• Digital multimeter for solenoid and voltage tests
• Sprinkler head key or small flat screwdriver for adjustments
• Narrow trenching shovel and hand trowel
• PVC cutter, primer, cement and slip-fix couplings
• Waterproof wire connectors
• Spare nozzles, heads and a replacement solenoid matching your valve brand
• Pressure gauge for a hose bib

When to Call an Irrigation Pro

DIY handles heads, nozzles, solenoids and simple pipe breaks. Call a professional for backflow device repair or testing (often required by code), wire breaks you cannot locate (pros use wire tracers), a main line leak upstream of the valves, repeated valve failures or a system that needs redesign. You can find local lawn and irrigation pros through our services directory. If repairs are piling up on an older system, compare costs in our sprinkler system installation cost guide.

Prevention saves most service calls: winterize properly in cold climates (see how to winterize a sprinkler system), walk every zone monthly during the season and keep mower blades clear of head tops. For more on watering and turf health, visit the lawn care guide.