Common irrigation system faults and their repair

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Common irrigation system problems and their repair

An automatic irrigation system is an almost invisible part of the garden for many gardeners – when it works, you don't notice it. But when it stops working, the garden quickly makes it noticeable: the lawn turns yellow, flower beds wilt, or on the contrary – the sidewalk is wet and you pay for a wasteful system that repeats watering cycles endlessly without reason. Over the years of practice, I have seen dozens of different faults, from trivial clogs in drip emitters to complicated faults in control units with damaged logic. In this article, I will systematically go through all common types of faults, explain the causes, principles and practical repair procedures so that you can solve most problems yourself – without calling a technician.

If you are still planning the installation and want to avoid problems before they occur, I recommend reading the article Installation of an automatic irrigation system step by step, where the most common errors during the initial installation are described, which are the source of later faults. Equally useful is the article Maintenance and winterization of the irrigation system – proper preparation for winter and spring start-up eliminates a large part of the faults we will deal with here.

Why do irrigation systems fail at all?

Before we move on to specific faults, it is important to understand what the system causes of faults are. An irrigation system works under extreme conditions: it is constantly exposed to water pressure, UV radiation, frost, heat, ground moisture, plant roots, insects and mechanical stress from mowing or digging in the garden. No other home installation is similarly exposed to so many influences at once.

Failures can be divided into several basic categories:

Mechanical failures – physical damage to pipes, sprinklers, drip emitters or fittings
Hydraulic failures – incorrect pressure, flow or air in the pipe
Electrical and control failures – faults in the control unit, solenoid valves or sensor technology
Biological and chemical clogs – calcium deposits, biological film, algae, root infiltration
Failures caused by incorrect installation – incorrect setting, underdimensioning, incorrect zoning

Sprinklers – faults and repairs

Sprinklers are the most mechanically sophisticated part of the system and at the same time the most common source of faults. Each sprinkler contains an internal piston, filter, nozzle and spring – dozens of moving parts exposed to ground moisture and abrasive particles in the soil.

Sprinkler does not pop up or only partially

This is one of the most common faults. The internal piston of the sprinkler is stuck inside and the nozzle does not water the expected sector. The causes are mostly the following:

Clogged nozzle or filter – soil, gravel or biological film block the free movement of the piston. Solution: disassemble the top part of the sprinkler (turning counterclockwise), remove the filter and rinse under pressure with clean water. Clean the nozzle with a thin needle or pin. Do not use wire – you will damage the calibrated hole.
Damaged spring – after several years, the spring loses elasticity and the piston does not return to the basic position. Solution: replace the internal module of the sprinkler or the entire body. Most manufacturers sell replacement internal modules separately.
Low water pressure – if the pressure in the network drops below the recommended 2–2.5 bar, the sprinkler does not have the energy to lift the piston. Solution: check the pressure at the system inlet; if it is a zonal issue, look for a leak or too many sprinklers on one zone. More about the required pressure can be found in the article What pressure and flow do I need for irrigation.

Sprinkler leaks even after the zone is turned off

Typical symptom: after the control unit closes the zone, water still flows from the sprinklers at the lowest point in the garden for a few minutes. This is almost always so-called low head drainage – water draining from the pipes through the lowest lying sprinklers by gravity. Sprinklers have a built-in valve preventing this phenomenon (check valve), but it can become clogged or worn. Solution: replace the sprinkler module with a variant with a functional check valve. The new generation of sprinklers has check valves resistant to pressure differentials of 0.3–0.55 bar. If the garden has a pronounced elevation profile (more than 1.5–2 m elevation on one zone), also consider installing an automatic air vent valve at the end of the pipe.

Sprinkler does not rotate or has a limited sector

Rotating sprinklers have an adjustable rotation angle. If they stop rotating completely, the cause is most often mechanical blockage (a stone caught in the gear mechanism) or gear wear. Solution for a stone: disassembly and flushing. For gear wear: replacement of the internal mechanism. The sector is adjusted with a small screwdriver at the top of the sprinkler – a red or white mark indicates the right extreme point, the left is fixed. Turning the adjustment element clockwise expands the sector, counterclockwise narrows it.

Drip irrigation – typical faults

Drip systems suffer from a different range of faults than sprinkler systems. Their main Achilles' heel is clogging – either by sediment, lime scale, or biological film. A more detailed comparison of both types can be found in the article Drip vs. Sprinkler Irrigation – What is Better for Your Garden Type.

Clogged emitters or drippers

A dripper has a calibrated flow rate usually of 2, 4, 8 or 16 l/h. If it becomes clogged, the plant receives less water than it needs, but you may not see it on the surface – the dripper in the soil does not leak, nor does it water. Diagnosis: when starting the zone manually, check each emitter – it should form a visible wet spot or drip gently. A dry emitter is clogged.

The solution depends on the degree of clogging:

Mild deposit: unscrew the dripper and soak it in a vinegar and water solution (1:1) for 30–60 minutes. Then rinse it under clean water.
Moderate deposit: a special cleaning solution based on citric acid applied through a hose fitting – fill the system with the solution and let it work for 2–4 hours.
Heavy clogging: replace the emitter. Drippers are cheap (just a few cents each), so it makes no sense to spend time on lengthy cleaning.

Prevention: install a mesh filter with 130–200 mesh (0.12–0.08 mm) at the inlet to the drip zone. Even if you have a filter at the inlet to the entire system, drip lines require finer filtration than sprinkler zones. In areas with hard water (hardness value over 300 mg/l CaCO₃), consider regular acid-based prevention – once a month, run a diluted citric acid solution (2 g/l) through the system for 10 minutes.

Cracked or damaged drip hose

Mice, voles, as well as sharp stones or garden tools are the most common culprits. A leak in a drip hose is detected by a large wet spot on the surface that is not related to any emitter. Finding the exact location of the leak: start the zone manually and slowly walk along the hose route. A crack in a buried hose will reveal itself by bubbles or a fountain of water spilling to the surface.

Repair: cut the hose cleanly at the damaged spot (not diagonally – it must be a straight cut perpendicular to the hose axis). Insert a hose coupling (coupling insert), which connects both ends. These couplings are available with sealing or threaded versions – both types are watertight and durable. For larger diameter hoses (20–25 mm), use standard LDPE hose fittings with O-ring sealing.

Solenoid valves – faults and diagnostics

A solenoid valve is the bridge between the electrical control unit and the hydraulics. When the control unit sends a 24 V AC pulse, the electromagnetic coil opens the valve and water can flow into the zone. Solenoid faults are responsible for a large portion of "non-functional zones".

The zone does not open (no water)

If the zone does not water at all, the diagnosis proceeds in three steps:

Electrical check: measure the resistance of the solenoid coil with a multimeter (ohm range). The standard value for a 24 V AC solenoid is 20–60 Ω. A value of "0 Ω" means a short circuit (burned coil), a value of "∞" (infinite) means a broken circuit. In both cases, the solenoid head must be replaced.
Power check: measure 24–28 V AC on the solenoid terminals when the zone is turned on with a voltmeter. If there is no voltage, the problem is in the wiring or the control unit, not in the solenoid.
Manual test: most valve heads have a manual activation – turn the small plastic screw or lever on the solenoid counterclockwise by ¼ turn. If the valve works mechanically and water flows, the problem is electrical. If water does not flow even when manually opened, the problem is hydraulic (clogged membrane).

The zone does not close (continuously running zone)

This fault causes huge water losses and can flood the garden. Causes:

Contamination under the membrane – the most common cause. A small grain of sand or another solid object prevents the membrane from closing. Solution: turn off the main water shut-off, remove the solenoid head (4–6 screws), remove the membrane, rinse the area with water and rinse the membrane. Check if the membrane is torn.
Torn membrane – after years of operation (typically 7–12 years), the rubber hardens and cracks. Replacing the membrane is a trivial repair taking 10 minutes.
Damaged solenoid coil – rarely, if the coil remains in a permanently activated state (short in a certain position), the valve remains open. Replace the entire solenoid head.

Control unit – faults and settings

The control unit (timer, programmer) is the brain of the entire system. Modern units are robust, but they also have their weaknesses – primarily sensitivity to moisture and power outages.

The unit does not start programs

Causes and solutions in order of probability:

Dead backup battery – after a power outage, the internal clock resets. The unit thinks it is a different time than you set, or the program does not start at all. Replace the battery (usually 9V or AA), and set the current time and day.
Active "Rain" or "Sensor bypass OFF" function – the rain sensor reports wet conditions and blocks irrigation. Check whether the sensor is signaling rain even in dry weather (worn wiper plate).
Incorrect program configuration – the start time is wrong, days are turned off, or the watering duration is 0 minutes. Go through the settings step by step according to the manual.
Internal electronics failure – after several years of operation, capacitors may dry out. Solution: replace the control unit. Modern units (WiFi smart controllers) are compatible with existing wiring and offer much more advanced features.

Some zones are not activatable from the control unit

If the control unit activates, for example, zones 1, 2 and 4, but not zone 3, look for a problem in the wiring of that zone. Procedure: disconnect the wires of zone 3 from the control unit and measure the resistance of the solenoid directly at the cable terminals – if you get the correct 20–60 Ω, the problem is in the unit (zone 3 output is faulty). If the resistance is out of range or infinite, look for a cable break underground or a problem with the solenoid.

A cable break underground is one of the most difficult faults to locate. Using a reflectometer (TDR – time domain reflectometer, available for rent from electricians) you can accurately determine where the cable has broken. Alternatively: if you know the cable route, you can systematically check the voltage at several points from the control unit towards the solenoid.

Hydraulic faults – pressure, air and leaks

Irrigation is essentially a hydraulic circuit and many faults are related to incorrect pressure or flow. More about hydraulic design can be found in the article What pressure and flow do I need for irrigation.

Too low or too high pressure

The optimal operating pressure for most sprinkler systems is 2.5–4.0 bar. Drip systems operate at lower pressure, typically 1.0–2.5 bar. Measuring pressure: install pressure gauges at the system inlet and ideally also at the end of the longest branch.

Too low pressure (below 2 bar for sprinklers): sprinklers do not extend fully, the spray range is shortened, rotating heads do not start turning. Causes: insufficient pressure in the household network (common when connected to a well without a pressure tank), or too many sprinklers open at once. Solution: check the pressure tank, redistribute a large zone into two smaller ones, or install a pressure-reducing/increasing valve.

Too high pressure (above 5–6 bar): sprinklers mist instead of watering (so-called misting effect) – droplets are too small and evaporate before reaching the ground. This leads to rapid wear of seals. Solution: install a pressure-reducing valve before the system. Standard PRV valves for garden systems are set to the desired output pressure (2.5–3.5 bar).

Air in the pipes

Air blockages are a sneaky fault – the system appears to be working, but some sprinklers produce irregular flows, sputter or do not water at all. Air gets into the system during winter draining (if you used a compressor), during repairs with drained pipes, or during pressure drops. Solution: manually open several sprinklers at once (or safety valves at the end of branches) and let the system flow at low speed – air will gradually be pushed out. Automatic air vents at the end of pipes solve this problem automatically.

Locating water leaks underground

A leak in buried piping is indicated by a wet spot on the surface or unexplained high water consumption. Systematic localization:

Turn off all zones, keep the main valve open. If the pressure gauges still show a drop, the leak is in the main pipe before the valves.
Open each zone one by one and watch for which zone the pressure drops too quickly or the wet spot grows.
In the affected zone, gradually close sections of the pipe (if section valves are available) or search visually.
Use garden probing – a thin metal rod inserted into the ground will reveal where the soil is significantly wetter.

Rain sensor and soil sensors – faults

A rain sensor is a small device that interrupts the irrigation cycle during rain. It is one of the most effective ways to save water (more in the article How to save water in garden irrigation), but it is also a source of confusing faults.

Rain sensor blocks irrigation even in dry weather

Causes:

Slow drying of the wick plate – wick-type sensors work on the principle of a hygroscopic wick. If the sensor was in a humid environment (dense vegetation, north-facing wall where the sun does not shine), the wooden or plastic plate dries slowly. Solution: move the sensor to a location with better air circulation and sunlight.
Sensor is dirty or deformed – calcium deposits, lichens or mechanical damage change the characteristics of the hygroscopic plate. Solution: clean, or replace the wick (sold as a spare part).
Sensitivity setting – most rain sensors have adjustable sensitivity (3–25 mm of precipitation). With too low sensitivity, the sensor activates even with minimal rain and remains active for a long time. Increase the threshold.

Soil moisture sensor reports incorrect values

Capacitive soil sensors measure the electrical permittivity of the soil, which depends on the water content. Faults:

Poor contact of the sensor with the soil – if there is air around the probe (incomplete backfilling, soil settlement), the readings are distorted. Solution: remove the sensor, backfill the probe hole and reinsert the sensor.
Calibrated for a different soil type – sensors are calibrated for a specific soil type (sandy, clay, loamy). In a different soil, they may measure 20–40 % differently. Solution: recalibrate via the app or control unit according to the soil description.
Probe corrosion – cheap resistive sensors corrode after 1–2 years, calibration shifts. We recommend capacitive sensors made of stainless steel or sensors with a polymer probe.

Winter damage and system protection

The most extensive faults occur every year in spring – the consequence of improper or no winterization of the system. Frost can cause damage by cracking pipes, sprinklers and valve bodies, resulting in hundreds of euros in damage. A detailed winterization procedure can be found in the article Maintenance and winterization of an irrigation system.

Typical winter damages and their repair:

Cracked plastic sprinkler body – visible cracking of the casing. Replace the entire sprinkler. The pressure of ice when water freezes is incredibly high – up to 900 kg/cm², no plastic can withstand it.
Cracked valve body – you will notice it in spring when you turn it on for the first time. Deformed plastic or brass valve body leaks even when closed. Replace the valve.
Deformed control unit of the outdoor installation – if water has entered the housing and frozen, the display or PCB may be damaged. Prevention: the control unit housing must have at least IP54 protection rating for outdoor installation.

Filtration – neglected, yet crucial element

Most clogs in sprinklers and drippers originate in the filter – more precisely, in the absence or neglect of filtration. Every garden irrigation system should have a central filter at the inlet. The standard fineness for sprinkler systems is 80–100 mesh (approx. 0.15 mm), for drip systems 130–200 mesh (approx. 0.08 mm).

The service interval of the filter depends on the quality of the water source. With municipal water supply (relatively clean water, low sediment content), cleaning 2–3 times a year is sufficient. With connection to a well, stream, or rainwater, cleaning may be needed every 2–4 weeks during the season. A clogged filter shows the same symptoms as low pressure – short spray range, sprinklers not extending.

Systems connected to rainwater collection (more in the article Irrigation with recycled rainwater – what you need to know) require two-stage filtration – a coarse filter 200–400 μm captures leaves and large impurities, a fine filter 80 μm ensures purity for emitters.

When to call a professional and when to fix it yourself

Most common faults – cleaning of sprinklers, membrane replacement, cleaning of drippers, setting the control unit, solenoid replacement – can be handled by a skilled gardener. Basic tools are needed (screwdriver, pliers, multimeter, hose fittings) and a stock of common spare parts (membranes, nozzles, hose couplings).

I recommend calling a professional in these situations:

Locating a leak in a deeply buried main pipe (requires TDR measurement or extensive digging)
Complete system inspection after winter damage (multiple cracked pipes)
Hydraulic faults after garden reconstruction (changed geometry, new lawn, zones need to be redesigned)
Integration of sensor systems, WiFi controllers, or connection to home automation
Malfunctions in pressure tanks or hydro pump stations (these devices follow different rules)

Preventive maintenance – the best repair is the one that wasn't needed

From experience, I know that customers who perform regular preventive maintenance have significantly lower repair costs and a longer lifespan of the entire system. Here is a recommended schedule:

Every 2 weeks during the season:

Visual inspection of sprinklers – do all of them extend? Is there any leakage?
Check soil moisture at a reference point in the garden

Monthly:

Clean the mesh filter at the inlet
Check the pressure on the inlet pressure gauge
Acid-citric prevention for drip zones (once a month with hard water)

Start of the season (spring):

Complete visual inspection of all sprinklers, identifying winter damage
Test each zone by manually turning it on
Set or revise programs in the control unit – adjust to spring/summer/autumn mode
Replace the battery in the control unit (if it uses a backup battery)

End of the season (autumn):

Drain the system and blow it out with a compressor (2–4 bar, no more – risk of damaging sprinklers)
Close the main valve and protect components from frost
Store the control unit indoors or cover it with an insulating cover

Most frequently asked questions (FAQ)

Why is the sprinkler watering outside the sector I set?

The most common cause is wear of the sealing between the rotating nozzle and the sprinkler body. Water leaks around the seal and flows into the gap – it appears to be watering "beside". Solution: disassembly, check the seal and replace it. Another possible cause is sediment that mechanically blocks the return of the nozzle to the correct position after rotation. Cleaning the internal mechanism usually solves the problem.

My system is watering correctly, but water consumption is too high. Where to look?

If the system visually works correctly, but your water bill has increased, look for small leaks that are not visible on the surface – neglected fittings seals, micro-cracks in hoses or a slowly leaking solenoid that is not fully closed. Close the main valve of the system and observe the water meter for 15–30 minutes – if the needle moves, the system is leaking somewhere even when the zones are off. Systematically search for the leak location according to the procedure described in the section on hydraulic faults.

The control unit reports "Error" or "Fault" on one of the zones. What does it mean?

Most modern control units measure the current draw of solenoids. A zone error message usually means that during an attempt to open, the unit did not detect an electrical circuit – a broken cable, a disconnected solenoid, or a solenoid with a broken coil. Less frequently, it may be a short circuit (damaged cable insulation in the ground). Solution: measure the resistance of the solenoid directly at the control unit terminals and compare it with normal values (20–60 Ω).

Rotors have different throw distances – some reach far, others only a little. Why?

There are several reasons: clogged nozzles (varying levels of dirt), different heights of the rotors above the ground (one is buried too deep, another protrudes too high), or different actual pressure in various parts of the zone (hydraulic imbalance). First, check the filters and nozzles. Then adjust so that all rotors protrude evenly. If the throw distance is still uneven, the system needs to be balanced – for example, using pressure-regulated nozzles (pressure-regulated nozzles, PRS).

The system starts irrigation in the middle of the night, even though I did not program it. What is happening?

This is almost always an issue with the control unit – either a second, forgotten program is set (most units have programs A, B, C, each with its own start times), or the unit is in demo/test mode. Check all program channels of the unit and delete or deactivate those you do not need. If the problem persists after a complete reset, it may be an internal electronics failure.

How long will an irrigation system last without major repairs?

With proper installation, regular maintenance, and thorough winterization, a quality garden irrigation system can last 15–20 years without the need for major reconstruction. PE pipes (LDPE, HDPE) have a lifespan of 30–50 years. Rotors and solenoid valves typically last 8–15 years. The control unit lasts 7–12 years. The shortest lifespan is that of drip emitters in sandy soils – 3–6 years. Regular replacement of small parts (diaphragms, nozzles, emitters) will keep the entire system fully operational in the long term, without the need for complete replacement.

Conclusion: a systematic approach to faults saves time and money

Most irrigation system faults appear mysterious at first glance, but usually have very logical and simple causes. The key to successful repair is a systematic approach: diagnosis from the source toward the consumer, measuring actual values (pressure, resistance, voltage) instead of guessing, and understanding how hydraulics and electricity interact within the system.

An investment in a few basic measuring tools (a pressure gauge and a multimeter), a stock of common spare parts, and at least one annual service will save you significantly more in the long run than they cost. And your garden will reward you – with healthy greenery throughout the season, even when you are away on vacation.

If you are planning to install or upgrade a system, also check out other articles in our Knowledge Center: How to choose the right irrigation system for your garden, How to design irrigation zones for your garden, lawn and flowerbed, and Common questions about garden irrigation, where you will find a comprehensive foundation for trouble-free operation of your system for many years to come.

Do you have a question about this topic?

Not sure what to do or dealing with a specific situation in your home? Write to us – we are happy to help.