How to Maintain a Pressure Washer
To maintain a pressure washer, check the engine oil and change it if it is dark or low, check and change the pump oil separately, inspect the inlet water filter screen for debris, check the high-pressure hose for cracks, test the spray tips, and run water through the pump for 1 minute before starting the engine.
- Time
- 20 min
- Frequency
- every spring (before first use)
- Difficulty
- easy
- Cost
- $10
What you'll need
- Socket wrench set
- Funnel
- Shop rags
- Garden hose
The steps
- 1
Check engine oil and change if dark or low
Pull the engine oil dipstick and check the level and color. Clean oil is amber or light brown. Dark, gritty, or milky oil needs changing. Drain the old oil into a pan, replace the drain plug, and refill with the oil type specified in your engine manual (usually 10W-30). This is the same process as any small engine oil change.
- 2
Check pump oil
The pump has its own oil supply, separate from the engine. Most pumps have a sight glass or dipstick on the pump housing. The oil should be clear or milky-white (pump oil is different from engine oil). If it is dark or low, drain it and refill with pump oil rated for your pressure washer. Never use engine oil in the pump.
- 3
Inspect the inlet water filter screen
Unscrew the garden hose fitting from the pump inlet and look at the small mesh filter screen inside. Remove debris, sediment, or mineral buildup. A clogged inlet filter starves the pump of water, causing it to run dry. Running a pressure washer pump without adequate water flow even briefly can cause permanent damage.
- 4
Check the high-pressure hose for cracks
Inspect the full length of the high-pressure hose. Look for cracks, bulges, kinks, or abrasion damage. A compromised hose can burst under pressure, which is a serious safety hazard. Replace any hose that shows damage. Also check the connections at both ends for corrosion or cross-threading.
- 5
Test spray tips
Attach each spray tip and pull the trigger briefly with the water running but the engine off (water pressure only). Verify that each tip produces the correct spray pattern. Clear any clogged tips with the cleaning pin that came with the machine or a small piece of wire. A partially clogged tip creates uneven pressure and can damage surfaces.
- 6
Run water through the pump for 1 minute before starting
Connect the garden hose, turn on the water supply, and squeeze the spray gun trigger to let water flow through the pump for a full minute before starting the engine. This purges air from the pump and primes the system. Starting the engine with a dry pump causes the seals to overheat and fail within seconds.
Engine oil vs pump oil
Gas pressure washers have two completely separate oil systems, and this catches many homeowners off guard. The engine has its own crankcase oil, just like a lawn mower or any other small engine. The pump — the component that pressurizes the water — has its own dedicated oil reservoir.
Engine oil is standard small engine oil: 10W-30 or SAE 30, changed the same way you would change oil in a mower. Pump oil is a lighter, non-detergent oil specifically formulated for the pump's seals and pistons. The two are not interchangeable. Using engine oil in the pump can swell or dissolve the seals, leading to leaks and pressure loss.
Check both before the first use of the season. Engine oil is accessed via a dipstick on the engine. Pump oil is typically visible through a sight glass on the pump housing. If either is dark, low, or milky (milky pump oil means water has entered the system), change it.
The inlet filter protects the pump
A pressure washer pump is a precision component running at high pressure. Debris in the water supply — sand, scale, small rocks, sediment — damages the pump valves and pistons. The inlet filter screen is a small mesh filter at the water inlet that catches this debris before it enters the pump.
Check this filter before every use. Unscrew the garden hose connection and pull the filter screen out. Rinse it under running water and reinstall. If the screen is torn or deteriorated, replace it. A clogged filter restricts water flow to the pump, which is almost as bad as running the pump dry. Inadequate flow causes cavitation — air bubbles that implode inside the pump and erode the internal components.
Winterizing prevents the most expensive failure
Freeze damage is the number one killer of pressure washer pumps. Water expands when it freezes. Water left inside the pump housing, valves, and hoses over winter can crack the pump casing or destroy internal seals. A replacement pump costs $100 to $300 depending on the model.
Before storing for winter, disconnect the garden hose and spray gun. Pour pump antifreeze (sold as "pump saver" or "pressure washer pump protector") into the water inlet and pull the starter cord a few times (without starting the engine) to circulate the antifreeze through the pump internals. This displaces the water and protects the seals and housing through freezing temperatures.
Never use automotive antifreeze. It is toxic and will contaminate whatever you spray the washer on next spring. Pump antifreeze is non-toxic and propylene glycol-based.
Storage with pressure released
After the last use of the season, always relieve the pressure in the system before storing. Shut off the engine, turn off the water supply, and squeeze the spray gun trigger until water stops flowing and the pressure drops to zero. Disconnect the hose and spray gun.
Storing a pressure washer with pressurized water trapped in the hose and pump stresses the seals continuously. Over months of storage, this constant pressure can cause seals to take a permanent set (deform), leading to leaks and pressure loss when you start up in spring. Releasing pressure takes 10 seconds and protects the pump for the off-season.
Frequently asked questions
- What is the difference between engine oil and pump oil?
- Gas pressure washers have two separate oil systems. The engine uses standard small engine oil (10W-30 or SAE 30) just like a mower. The pump uses a non-detergent pump oil that is lighter and formulated for the pump's seals and pistons. They are not interchangeable. Using engine oil in the pump can damage the seals.
- What is the number one cause of pressure washer pump failure?
- Freeze damage. Water left in the pump over winter expands when it freezes and cracks the pump housing or destroys the internal seals. If you live in a freezing climate, run pump antifreeze (pressure washer pump saver) through the system before storing for winter. This one step prevents the most common and expensive failure.
- Why does my pressure washer pulsate or lose pressure?
- Pulsating pressure usually means the pump is not getting enough water. Check the inlet filter for clogs, make sure the garden hose is fully turned on and not kinked, and verify the hose diameter is adequate (most washers need a 5/8 inch hose). Air in the system also causes pulsation — run water through the pump for a minute before starting.
- Do electric pressure washers need the same maintenance?
- Electric pressure washers have no engine oil to change, but the pump still needs attention. Check for inlet filter clogs, inspect the hose, test the spray tips, and prime the pump with water before starting. Some electric models have sealed pumps that do not require oil changes. Check your manual for your specific model.
Products you'll need
This section contains affiliate links. We may earn a commission at no cost to you.
Pressure Washer Pump Oil
Pump oil for pressure washer maintenance
As an Amazon Associate we earn from qualifying purchases. The Home Almanack may earn a commission on products purchased through links on this page, at no additional cost to you.
Never forget this task again
The Home Almanack tracks every maintenance task your home needs and reminds you automatically. Takes about 30 seconds to set up.
Get free reminders — never miss it againRelated guides
How to Power Wash Your Patio
Power wash your patio in about an hour with a pressure washer and a 25-degree nozzle. Do it once a year in spring to remove dirt, algae, and stains before they cause permanent discoloration.
How to Clean House Siding
Clean your house siding in about an hour with a garden hose, soft brush, and cleaning solution. Do it once a year in spring to prevent mold growth, extend siding life, and keep curb appeal high.
How to Aerate Your Lawn
Aerate your lawn once a year to break up compacted soil and promote deeper root growth. The job takes about an hour with a core aerator you can rent or buy.