Common Pressure Washer Problems and Solutions

Even well-maintained pressure washers occasionally develop problems. The good news is that most issues have straightforward causes and solutions that don't require professional repair. Before calling a technician or replacing your machine, work through this troubleshooting guide to identify and potentially fix the problem yourself.

We'll cover the most common problems in order of frequency, starting with issues you're most likely to encounter.

Low or Inconsistent Pressure

This is the single most common pressure washer complaint. If your machine isn't delivering the pressure it should, work through these causes in order:

Inadequate Water Supply

Symptoms: Low pressure, pressure that drops during use, pump making unusual noises

Cause: The pump needs adequate water flow to function properly. If inlet water is restricted, the pump can cavitate (run partly empty), damaging seals and reducing pressure.

Solution:

• Check that the tap is fully open
• Verify your garden hose can deliver adequate flow (typically 7-10 LPM minimum)
• Remove and clean the inlet filter—debris here is a common culprit
• Ensure the garden hose isn't kinked or partially blocked
• Check for leaks in the supply hose

Worn or Clogged Nozzle

Symptoms: Gradual pressure loss over time, uneven spray pattern

Cause: Nozzles wear with use, gradually enlarging the orifice and reducing pressure. They can also become partially blocked with scale or debris.

Solution:

• Remove the nozzle and clean with the included cleaning needle or thin wire
• Soak in vinegar solution to dissolve mineral deposits
• Compare to a new nozzle—if the orifice is visibly larger, replace it
• Nozzles are inexpensive; when in doubt, replace

Air in the System

Symptoms: Pulsating or surging pressure, sputtering spray

Cause: Air entering the pump through loose connections, low water supply, or after the machine has been stored.

Solution:

• With the machine off, squeeze the trigger for 30 seconds to purge air
• Check all connections for tightness
• Inspect O-rings at connection points for damage
• Ensure the inlet hose is below the water level if using a tank supply

Worn Pump Seals or Valves

Symptoms: Consistent low pressure that doesn't respond to other fixes, water leaking from pump

Cause: Internal pump components wear over time, especially if the pump has run dry or with inadequate water.

Solution:

• Pump rebuild kits are available for many models—replacing seals, valves, and O-rings can restore performance
• This repair requires mechanical confidence; consider professional service if unsure
• For older or budget machines, pump replacement or machine replacement may be more economical than repair

Pressure Washer Won't Start

Electric Models

No response at all:

• Verify the power outlet works (test with another device)
• Check the reset button on the motor or plug—some have thermal overload protection
• Inspect the power cord for damage
• Ensure any safety switches or trigger locks are disengaged

Motor hums but doesn't run:

• This often indicates a seized pump—the motor can't turn the pump mechanism
• Can occur after running dry or storing with water that caused scale/corrosion
• Try turning the pump shaft manually (disconnect power first)
• May require pump replacement or professional service

Petrol Models

Engine won't turn over:

• Check fuel level and fuel freshness
• Ensure the fuel tap is open
• Check the choke position (should be closed for cold start)
• Inspect the spark plug wire connection
• Check engine oil level—many engines have a low-oil shutoff

Engine turns but won't fire:

• Remove and inspect the spark plug—clean or replace if fouled or worn
• Check for spark by grounding plug against engine and pulling cord
• Verify fuel is reaching the carburettor
• Clean or replace the air filter
• Stale fuel is a common cause—drain and refill with fresh petrol

Water Leaking from the Pump

Symptoms: Water dripping or spraying from the pump housing, puddles under the machine

Possible Causes and Solutions

Loose connections: Check and tighten all fittings. Inspect O-rings and replace if damaged.

Worn pump seals: Internal seals wear over time. A pump rebuild kit can replace these, or the pump may need professional service.

Cracked pump head: Can occur from freeze damage or impact. Pump head replacement or complete pump replacement is needed.

Thermal relief valve: Some leaking is normal from this safety valve when the trigger isn't pulled and the pump runs—it prevents overheating. However, constant heavy leaking indicates a faulty valve that needs replacement.

Pulsating or Surging Pressure

Symptoms: Pressure cycles high and low rapidly, spray pulses rather than staying consistent

Common Causes

• Air in the system: Purge air by running with trigger pulled before starting pump
• Unloader valve issues: The unloader valve regulates pressure; if stuck or worn, it causes pulsing
• Inlet valve problems: Worn or stuck inlet valves prevent smooth pump operation
• Insufficient water supply: Marginal water flow causes intermittent cavitation

Work through water supply and air issues first. If pulsing persists, the unloader valve or pump valves likely need service.

Detergent Won't Dispense

Symptoms: No soap appearing in spray when using low-pressure soap nozzle

Solutions

• Verify nozzle selection: Detergent only draws at low pressure—use the black soap nozzle
• Check the siphon tube: Ensure it's fully submerged in detergent, not kinked, and not clogged
• Clean the injector: The chemical injector can clog with dried detergent—flush with clean water
• Verify detergent compatibility: Some thick detergents don't siphon well; dilute if necessary
• Check for damage: Cracked siphon tubes or damaged injectors need replacement

Machine Shuts Off During Use

Electric Models

• Thermal overload: Motor has overheated and protective circuit tripped. Allow to cool for 15-30 minutes
• Insufficient power: Long or undersized extension leads can cause voltage drop
• GFCI/RCD tripping: Ground fault detected. Check for damaged cords or moisture in connections

Petrol Models

• Fuel starvation: Low fuel, clogged fuel filter, or blocked fuel cap vent
• Low oil shutoff: Engine has triggered the low oil safety switch
• Overheating: Blocked cooling fins or running in extreme heat without adequate ventilation

Unusual Noises

Knocking or banging from pump: Often indicates cavitation (pump running without adequate water) or worn internal components. Check water supply immediately; continued operation causes expensive damage.

Squealing from motor: Failing bearings in electric motors. Usually indicates end-of-life for the motor.

Grinding sounds: Internal pump damage or foreign material in the pump. Stop immediately and investigate.

Excessive vibration: Worn pump components, loose mounting bolts, or damaged internal parts.

When to Seek Professional Help

While many issues are DIY-fixable, some situations warrant professional service:

• Internal pump damage requiring disassembly beyond basic seal replacement
• Electrical faults in motors
• Petrol engine problems beyond basic maintenance (carburettor issues, compression problems)
• Under-warranty equipment—DIY repairs may void coverage
• Safety-critical components like high-pressure hoses and fittings

A professional service can also diagnose issues you can't identify yourself and may identify problems before they become expensive failures.

Prevention Is Best

Most pressure washer problems are preventable with proper care:

• Never run the pump without water flowing
• Flush after using chemicals
• Use pump protector before storage
• Keep petrol engines properly maintained
• Store correctly between uses
• Inspect components regularly

For detailed maintenance procedures, see our guide on How to Maintain Your Pressure Washer.