Common Sprinkler Problems: Low Pressure, No Water, and Uneven Coverage — Diagnosis Guide
This revised guide keeps the original topic while adding a dated field review, measured troubleshooting steps, safety boundaries, and current irrigation sources.
A woman called me in tears. Her brand new $4,000 irrigation system was flooding her basement window wells. The installers had set the heads too close to the foundation. They aimed three rotors directly at the house walls. They programmed all zones to run for 60 minutes regardless of precipitation rate. I dug up the heads next to the foundation. I relocated them 4 feet outward. I adjusted the arcs away from the house. I cut the run times to 25 minutes per zone. That adjustment cost $200 and took two hours. The original installers had walked away from a system. That system would have caused thousands in foundation moisture damage.
I have diagnosed every common sprinkler problem across hundreds of service calls. I can tell you that nearly every issue falls into one of five categories. Those categories are coverage problems, pressure problems, mechanical failures, controller errors, and winter damage. Each category has a distinct set of symptoms and a clear fix path.
Why are there dry spots in my lawn even though the sprinklers are running?
Dry spots that persist when sprinklers run consistently point to one of three causes. One cause is a sprinkler head that has sunk below grade. It sprays directly into the grass canopy without clearing it. Another cause is an arc setting that misses the dry area entirely. The third cause is a clogged nozzle. A clogged nozzle reduces throw distance. The reduction is 30 to 50 percent from the manufacturer’s rated specification.
I find sunken heads by walking the dry zone during operation with the system running. I watch for heads that spray below the top of the surrounding grass. A pop-up riser should extend at least 2 inches above the soil surface when pressurized. If the grass blades are taller than the water stream, the spray never reaches the canopy. The grass directly around the head gets all the water. Everything beyond stays dry. I clear sunken heads by digging around the head’s body. I add a 2-inch or 4-inch PVC riser extension between the head and the supply line. Then I backfill with compacted soil. If the head height is correct, I check the nozzle for debris. I pop the nozzle cap off with a flathead screwdriver. I inspect the small openings with a flashlight. Sand, mineral deposits, and grass clippings lodge in nozzle openings. They distort the spray pattern into a narrow jet. I clean the nozzle with a small wire brush or a compressed air blast from a handheld duster. If cleaning does not restore throw distance, the nozzle has internal wear from abrasive well water. I replace the entire nozzle for $3 to $6 per head. I explain nozzle selection and performance characteristics in my guide for adjusting sprinkler heads. There I cover matching nozzles to site conditions.
What causes low water pressure in my sprinkler system?
Low pressure produces misting rather than solid water streams. Or it leaves heads barely popping up above the grass canopy. This problem typically stems from a partially closed main shutoff valve. It could also stem from a clogged valve filter screen. Or it could be a pipe leak that diverts flow volume away from the sprinkler heads.
I start by checking the main shutoff valve located at the house or at the meter. If the valve is only half-open, the entire system operates at reduced pressure. This happens regardless of the pump or municipal supply rating. I open the valve fully counterclockwise until it stops. If the valve is fully open but pressure remains low, I locate the valve manifold. I inspect each valve’s internal filter screen. This is a dome-shaped stainless steel screen that catches sediment before it enters the valve diaphragm chamber. I unscrew the valve bonnet. I lift the diaphragm assembly. I rinse the filter screen under running water. Sediment-clogged screens restrict flow to individual zones. They leave other zones unaffected. If the screens are clean, I listen for the sound of rushing water underground while the system runs. A whistling or gurgling sound at a specific location indicates a pipe leak. That leak drains water before it reaches the heads. I locate pipe leaks by walking the system while it runs. I look for unusually wet soil patches. I look for lush green grass strips that are greener than surrounding areas. I look for small depressions where water has washed away soil around the leak. I dig at the leak site. I cut out the damaged pipe section. I install a slip coupling with PVC primer and solvent cement. I also test static pressure at the nearest hose spigot while a zone runs. If static pressure drops by more than 15 PSI during operation, the supply line or meter is undersized for the system. I address pressure issues comprehensively in my sprinkler system components guide. There I explain pipe sizing and its effect on pressure.
Why are my sprinkler heads not popping up all the way?
Sprinkler heads struggle to pop up fully. Or they rise only partially above the grass canopy. This issue has one of three causes. The first is a blocked wiper seal that binds the stem against the barrel. The second is insufficient operating pressure below the head’s rated minimum of 15 to 25 PSI for spray heads. The third is a broken spring that cannot lift the internal riser column.
I test each head manually. I pull the stem upward with gentle hand pressure. If the stem rises smoothly and holds position, the spring and seal are functional. In that case the problem is system pressure. If the stem resists upward movement or feels gritty, the wiper seal around the stem has accumulated mineral deposits and dirt. This binds the stem to the barrel. I retract the stem fully. I apply a spray lubricant formulated for irrigation components around the wiper seal gap. I cycle the head several times by pushing the stem down and pulling it up. This distributes the lubricant. If lubricating the wiper seal does not solve the binding, I remove the entire head. I disassemble the internal riser assembly. I clean the barrel and wiper seal with a soft brush and warm water. I inspect the spring inside the head. If the spring has rusted or lost tension, the head will not pop up even with adequate pressure. A replacement spring costs $2 to $4. It slides into the head body without removing the head from the riser. If I replace the spring and the head still fails to pop up, the wiper seal has hardened from UV exposure. I must replace it along with the entire head for $8 to $15. I then check the operating pressure at the head location after spring replacement. I install a pressure gauge on the nearest hose spigot. If the reading remains below 25 PSI, the supply problem traces back to the valve or main line. I discuss valve-related pressure problems in my leaking sprinkler valve guide. There I cover diaphragm and solenoid issues that affect downstream head performance.
How do I fix sprinkler heads that leak water after the system shuts off?
Heads continue dripping or weeping water for several minutes after the zone valve closes. This indicates low head drainage. Water left in the lateral pipe after the valve shuts drips out through the lowest head on each zone. Gravity pulls the standing water down to the lowest point in the pipe run. That point is usually a sprinkler head.
Low head drainage is a design condition rather than a component failure. But it causes soggy spots around the lowest heads. It can attract pests and promote fungal growth.
- I fix low-head drainage by installing check valves in the lowest heads on each zone. Check valve heads contain a spring-loaded seal. This seal blocks water from exiting the head when system pressure drops below 5 to 10 PSI. A head with a factory-installed check valve costs $10 to $15. A standard head costs $6 to $10.
- I swap the lowest two or three heads on each zone for check valve models. If low head drainage persists after installing check valve heads, the lateral pipe has a dip or sag. That dip traps more standing water than the check valve spring can hold back. I verify this by cutting the lateral line at the low point.
- I install a small drain valve that opens automatically when pressure drops. This allows trapped water to exit into a gravel sump rather than through the heads.
- I install a 6-inch-deep gravel sump at the drain valve location. This prevents soil erosion from the discharged water. I cover low-drainage scenarios in my drip irrigation types guide. There I explain how emitter placement affects drainage patterns.
References
Rain Bird — Irrigation System Troubleshooting
Penn State Extension — Troubleshooting Home Irrigation Systems
Maintenance review – last checked August 3, 2026
- Originally published or scheduled: 2026-06-11
- Last reviewed: August 3, 2026
- Decision focus: available flow, static and dynamic pressure, pipe losses, pump limits, filtration, and safe testing
- Status: Updated for current editorial use; local codes, water restrictions, equipment manuals, and site conditions still control the final decision.
This page is a practical irrigation reference, not a substitute for local plumbing, electrical, water-quality, backflow, or landscape regulations. A correct answer depends on the water source, pressure and flow, pipe size, soil, plant demand, slope, climate, and the actual equipment installed. Treat old product names, prices, pressure figures, and seasonal dates as starting points that need verification.
What should be checked before changing the system?
Record the symptom or goal, the affected zone, the date, the weather, the controller program, the water source, the pressure reading, and any recent repair. Check whether a valve is open, whether a filter or nozzle is blocked, whether a backflow device is installed correctly, and whether the system is mixing incompatible heads or emitters. For electrical work, shut off power and follow the controller and pump instructions. For compressed air, chemical injection, trenching, or backflow work, use the equipment manual and qualified local help when the task exceeds ordinary homeowner maintenance.
A repeatable field method
- Inspect the zone while it runs and mark every dry spot, leak, misting nozzle, flooded area, and low-pressure symptom.
- Test one variable at a time: valve operation, filter condition, pressure, flow, nozzle pattern, emitter output, sensor signal, or schedule.
- Compare measured output with the design intent instead of adjusting by appearance alone.
- Make the smallest change that addresses the measured cause.
- Run the zone again, check adjacent zones, and record the result.
- Update the valve, zone, part, setting, and date in a repair log.
Common failure modes
Avoid increasing run time to hide a clogged filter, replacing a nozzle without checking pressure, mixing spray and rotor precipitation rates in one zone, putting drip tubing after an unsuitable regulator, using graywater without checking local rules, or blowing compressed air through equipment that is not rated for it. Also avoid assuming that a smart controller’s recommendation is correct without checking the weather source, soil, plant type, and actual catch-can or flow observations. More water is not a universal fix; it can create runoff, disease pressure, nutrient movement, erosion, or root problems.
Verification and maintenance record
After the repair or installation, record the component, model, setting, pressure, flow, run time, date, and observed result. Recheck the zone after the next significant weather event and at the next seasonal startup or shutdown. Keep a photo of valve boxes, wiring, filters, and unusual fittings. A dated record makes future troubleshooting faster and helps a professional understand what has already been tested.
Sources and boundaries
Use current guidance from the U.S. EPA WaterSense program, USDA Natural Resources Conservation Service, local water utilities, manufacturers, and the authority having jurisdiction. Local rules control backflow, graywater, fertilizer injection, wells, discharge, trenching, and licensed work.
- EPA WaterSense irrigation
- EPA WaterSense labeled controllers
- USDA NRCS irrigation water management
- Irrigation Association backflow prevention resource