Pressure Washer FAQs and Troubleshooting Advice

Cold-water pressure washers are suitable for removing mud, dust, loose dirt and general surface contamination. Hot-water pressure washers are more effective against oil, grease, animal fats and ingrained deposits because heat helps break down the contamination.

For industrial or frequent cleaning, the correct machine will depend on the required pressure, water flow, operating temperature, power supply and expected daily usage.

Contact Flowjet for machine-selection advice.

The water supply must provide at least the flow rate required by the pressure washer. Ideally, it should provide a small amount more than the machine’s rated litres per minute.

For example, a pressure washer rated at 15 LPM should receive a reliable supply of more than 15 litres per minute. An inadequate supply can cause pressure fluctuation, pump cavitation, vibration and premature seal damage.

You can carry out a basic flow test by timing how long it takes to fill a container of a known volume.

Pressure provides the force needed to loosen dirt, while water flow carries the loosened dirt away. A machine with high pressure but insufficient water flow may clean a small area aggressively without rinsing the surface efficiently.

Commercial and industrial cleaning often benefits from a balanced combination of pressure and water flow rather than simply choosing the machine with the highest pressure rating.

Some pressure washers can draw from a suitable water tank, while others need a pressurised or gravity-fed supply. The tank, inlet hose, fittings and filters must be correctly sized to avoid restricting the pump.

Never assume that a machine is self-priming. Contact us with the machine model and intended installation before connecting it to a tank.

Many commercial pressure washers can operate with longer hoses, but pressure loss increases with hose length and decreases with a larger internal hose diameter.

The correct hose depends on the machine’s pressure, water flow, temperature and total required length. All hoses, fittings, guns and reels must be rated above the maximum operating pressure and temperature.

View high-pressure hoses.

A non-marking hose is recommended where a standard black hose could leave marks on floors, walls or equipment. Blue and grey non-marking hoses are commonly used in food production, hygiene-sensitive environments, workshops and indoor cleaning areas.

Hose colour alone does not confirm food suitability. Always check the specification for the application.

Electrically heated industrial pressure washers normally require a reliable three-phase electrical supply with a neutral connection.

Common supply requirements include:

• 415V, 32A three-phase with neutral
• 415V, 63A three-phase with neutral

Requirements vary considerably between machines. A qualified electrician should confirm the available supply before a machine is ordered or installed.

Many electrically heated pressure washers are designed to provide water at approximately 80°C, but the achievable temperature depends on the machine, heating capacity, inlet-water temperature and water flow.

Always check the individual machine specification rather than assuming every electrically heated model will provide the same temperature.

Some electrically heated machines preheat water in a storage tank. Tank capacities commonly range from approximately 80 to 150 litres, depending on the model.

During continuous spraying, the stored hot water may be used faster than the heating elements can recover the temperature. This can cause the outlet temperature to fall.

Intermittent use gives the machine more time to reheat the water between cleaning periods.

Please consider:

• The available electrical supply
• Required pressure and water flow
• Required operating temperature
• Continuous or intermittent use
• Expected operating hours per day
• Available inlet-water flow
• Required hose length
• Indoor or outdoor installation
• Whether a non-marking hose is required
• Whether detergent or foam will be used

Milky pump oil normally means that water has mixed with the oil and caused it to emulsify.

Possible causes include:

• Worn water seals
• Worn oil seals
• A cracked or damaged ceramic piston
• Condensation or water entering the pump housing

The cause should be investigated before simply replacing the oil. Continuing to operate the pump may cause further internal damage.

Possible causes include:

• Insufficient or contaminated fuel
• A blocked fuel filter or fuel nozzle
• Worn or incorrectly adjusted ignition electrodes
• A dirty or faulty flame sensor
• Insufficient fuel-pump pressure
• A faulty thermostat, pressure switch or flow switch
• A faulty fuel solenoid
• A worn fuel-pump drive
• A failed ignition transformer or electrical component

Burner systems involve fuel, electricity and high temperatures. Repairs and combustion adjustments should be carried out by a suitably qualified engineer.

Hose vibration or pulsing pressure is commonly caused by an inconsistent water supply or a problem with the pump valves.

Check for:

• Insufficient inlet-water flow
• A blocked inlet-water filter
• Air entering through an inlet fitting or chemical valve
• A kinked or collapsing inlet hose
• Debris trapped in the pump valves
• Worn or damaged pump valves

Stop the machine if it is being starved of water, as continued use can damage the pump.

Turn the machine off if no water is reaching the pump. Running a pressure washer dry can damage its seals and internal components.

Check that:

• The water supply is turned on
• The supply provides sufficient water flow
• The inlet filter is clean
• The inlet hose is not kinked or collapsing
• Inlet fittings and hose clips are secure
• The trigger gun, lance or nozzle is not blocked
• The chemical inlet valve is not drawing in air

If water reaches the machine but there is still no outlet flow, stop using it and contact a pressure washer engineer.

Common causes include:

• An incorrect, oversized or worn pressure washer nozzle
• Insufficient inlet-water flow
• A blocked inlet filter
• Air entering the pump inlet
• Worn pump seals
• Worn or contaminated pump valves
• A faulty or incorrectly adjusted unloader valve
• A leak in the hose, trigger gun or fittings

Start by checking the water supply, filter and nozzle. Do not adjust the unloader valve unless you have suitable pressure-testing equipment.

Possible causes include:

• The machine is operating in high-pressure mode
• The detergent nozzle or low-pressure setting has not been selected
• A blocked chemical filter, hose or injector
• An air leak in the detergent hose
• Detergent that is too thick
• A worn or incorrectly sized chemical injector
• Excessive high-pressure hose length

Some pressure washers can only apply detergent at low pressure. Check the manufacturer’s instructions before dismantling the injector.

Possible causes include:

• A restricted water supply
• An electrical supply or voltage problem
• Motor overload or overheating
• A faulty pressure switch or flow switch
• A problem with the total-stop system
• A blocked nozzle causing excessive pressure
• Low oil, low fuel or another machine safety device

Do not repeatedly restart a machine that continues to trip or stop. Isolate it and arrange an inspection.

Service frequency depends on operating hours, water quality, environment and how heavily the machine is used. A heavily used industrial machine may require several inspections or services each year, while a lightly used machine may be serviced annually.

Regular servicing can identify worn seals, valves, filters, hoses and safety components before they cause a breakdown.

View our pressure washer repair services.

Yes. Send us clear photographs of the part, machine, connection sizes and machine identification plate. Please also include any visible manufacturer names or part numbers.

Measurements should be taken carefully because similar-looking fittings may have different thread types or sizes.

Send us a parts enquiry.

Yes. Flowjet supplies genuine and compatible replacement parts for a wide range of commercial and industrial pressure washer brands.

Where a compatible component is offered, the product description will identify the relevant machine or pump models. Please compare part numbers and specifications before ordering.

Shop pressure washer parts by brand.

The correct nozzle size is determined by the machine’s water flow and operating pressure. A nozzle that is too small can overload the pump, motor or engine. A nozzle that is too large will reduce the operating pressure.

Use the machine’s rated litres per minute and working pressure when selecting a nozzle.

View our pressure washer size charts.

Important points include:

• The total floor area
• How frequently the floor is cleaned
• The type and condition of the floor
• Doorway, aisle and racking widths
• Ground-floor, mezzanine or lift access
• Pedestrian or ride-on operation
• Disc, cylindrical-brush or pad cleaning
• Available water filling and drainage points
• Battery runtime and charging arrangements
• Whether people will be working nearby
• Available budget and ongoing maintenance costs

Providing floor measurements and photographs will help us recommend a suitable machine.

Important points include:

• Indoor, outdoor or combined use
• The total area to be swept
• The type and size of debris
• The amount of fine dust present
• Pedestrian or ride-on operation
• Battery, petrol, diesel or dual-power operation
• Required sweeping width
• Doorway and overhead-height restrictions
• Aisle and racking widths
• Ramps and required climbing ability
• How and where the waste hopper will be emptied
• Battery charging and machine-storage arrangements

ATEX relates to equipment and working environments where potentially explosive atmospheres may be present. An explosive atmosphere can be created by flammable gases, vapours, mists or combustible dust mixed with air.

Equipment used in a classified hazardous area must be suitable for the substance, zone and operating conditions. The customer or site operator is responsible for obtaining a suitable hazardous-area assessment and confirming the required equipment classification.

Do not select ATEX equipment solely from a general product description. Contact us with the complete site classification and intended application.

• Zone 0: An explosive gas atmosphere is present continuously, for long periods or frequently.
• Zone 1: An explosive gas atmosphere is likely to occur occasionally during normal operation.
• Zone 2: An explosive gas atmosphere is not likely during normal operation and, if it occurs, will exist only briefly.

• Zone 20: An explosive atmosphere involving combustible dust is present continuously, for long periods or frequently.
• Zone 21: An explosive atmosphere involving combustible dust is likely to occur occasionally during normal operation.
• Zone 22: An explosive atmosphere involving combustible dust is not likely during normal operation and, if it occurs, will exist only briefly.

We make every effort to dispatch available stock for next-working-day delivery when cleared payment is received and the order is processed before 2pm.

Delivery times are not guaranteed. If an order is urgent, please contact us before ordering so we can confirm availability and the expected dispatch date.

Yes, but larger machines and equipment may require suitable lifting or offloading facilities at the delivery address.

Please tell us about restricted access or the absence of a forklift before ordering. Unless otherwise agreed, delivery and offloading can only take place on suitable hard, level ground close to the delivery address.

Inspect the goods as soon as they arrive. Record visible damage on the delivery paperwork where possible and take photographs of the goods and packaging.

Contact Flowjet promptly with your order details and photographs so we can investigate the issue.

Built-to-order, specially manufactured or customised products normally cannot be cancelled once production has started.

Please check that all specifications, electrical requirements, dimensions and items shown on the quotation are correct before placing the order.

For complete information, please read our Delivery and Returns and Terms and Conditions.