Pressure Washer FAQs

Whether you've never used a pressure washer before or if you use one for work, these frequently asked questions will help you troubleshoot, repair, and better understand your machine. 

How Do I Start My Electric Pressure Washer

1. Attach a garden hose between the water supply and the pressure washer. 
2. Attach a high-pressure hose between the spray wand and the pressure washer. 
3. Turn the water on. 
4. Depress the trigger on the spray wand to purge any water or air from the unit. 
5. Depress and hold the trigger to relieve built-up pressure within the pump; continue holding the trigger while switching the machine to the "ON" position. 

Why Won’t My Electric Pressure Washer Start? 

If an electric pressure washer fails to start, several components should be inspected. 

Extension cords should be avoided, as they can significantly shorten the machine's lifespan. If one must be used, it must feature 12-gauge wire if the length exceeds 25 feet. Using 16-gauge, 18-gauge, or lighter extension cords of any length will fail to supply adequate power to the pressure washer, preventing the motor from starting or running properly. This insufficient power supply can also cause fuses to blow or circuit breakers to trip. Operating an electric pressure washer on a light-duty extension cord will cause permanent damage to internal switches and the electric motor. 

If the machine makes no noise at all, the electrical cord is the first place to investigate. It should be confirmed that the cord is plugged directly into a wall outlet with a tight connection, and that the outlet provides adequate grounded power to operate the unit.  

For operator protection, electric power washers utilize a Ground Fault Circuit Interrupter (GFCI), which may occasionally trip. To reset the device, follow the instructions provided in the owner’s manual. 

Why Did My Electric Power Washer Suddenly Stop? 

Extension cords should not be used, as they can significantly shorten the machine's lifespan. 

If a unit stops unexpectedly, check the following: 

• Verify if the electric cord has become unplugged. 
• Check whether the GFCI has tripped. 
• Inspect the main fuse box to see if the circuit breaker has tripped. All cords should be replugged and breakers flipped if necessary. 

NOTE: To reset the GFCI, the unit must be plugged into a "working" outlet before pressing the "Reset" button. If the GFCI is not connected to a live power source, the switch will not reset. Additionally, a GFCI-protected cord should not be plugged into a GFCI-protected outlet, as this will likely cause the GFCI to trip repeatedly. 

An electric pressure washer requires a stable power supply, and no other high-amperage appliances should be running on the same circuit. High-amperage items—such as refrigerators, coffee machines, heaters, or additional motors—can cause fuses to blow or breakers to trip when used simultaneously with the pressure washer. 

If the motor has stopped making noise entirely, the issue could be a faulty power cord. If the motor has stopped but continues to hum, it is usually indicative of a faulty capacitor. In either case, these components must be tested to confirm the exact cause. 

Why is My Electric Machine Cycling? 

Cycling occurs when the motor turns on and off while the trigger on the gun is not being pulled. This behavior is specific to electric units, as most gas machines do not feature a pressure switch. 

When a power washer is connected to a water source and turned on, the motor runs for several seconds to build pressure. Once a specific pressure (PSI) is reached inside the pump, a pressure switch engages and shuts the motor off. When that built-up pressure is released by pulling the trigger, the pressure inside the pump drops, causing the motor to restart. Once the trigger is released, pressure builds again, and the motor turns off. 

Because the pressure switch reacts to any drop in pressure, leaks are the primary cause of cycling in a machine. If a unit is cycling, inspect the following: 

• Check Connections: Verify that all connections are tightened properly. Water leaking from a loose fitting can cause the unit to cycle on and off. 
• Inspect O-rings: Verify that the pressure hose has an O-ring at the connection point. If this ring is missing or damaged, the unit will cycle. 
• Monitor for Leaks: While the unit is running, look for any visible water leaks that could be triggering the motor to restart. 

Why Doesn't My Pressure Washer Reach Full Pressure? 

Pressure washers are designed to utilize high water pressure for fast and efficient cleaning. If a unit is failing to spray with sufficient force, several components should be inspected. 

For Gas and Electric Machines 

A loss of pressure can stem from various sources. The following steps should be taken first: 

• Inspect Hoses: Ensure the garden hose and high-pressure hose are not kinked, leaking, or blocked. The water source must be turned on to full force and must supply the specific volume of water (GPM) outlined in the owner's manual. 
• Clean the Inlet Filter: The water inlet filter should be removed and checked to ensure it is free of debris. 
• Check Accessories: The trigger gun and nozzles should be inspected and cleaned if necessary. 

If these steps are completed and the pressure continues to fluctuate between high and low, air may be trapped in the pump. To re-prime the pump and remove trapped air, the machine should be turned off, and the high-pressure hose and trigger gun should be disconnected. With only the garden hose connected, the water source should be turned on to allow water to flow through the pump for 20 to 30 seconds. After turning the water off and reconnecting the pressure hose and gun, the machine can be tested again. 

For Electric Machines 

In electric models, low pressure is often accompanied by surging, cycling on and off, or continuous running. This behavior typically indicates that the machine is losing pressure through a leak, either in the external lines or inside the unit’s casing. The machine attempts to compensate for this pressure loss by running more frequently or with greater intensity than necessary. 

Why is My Pressure Washer Surging? 

While the causes of pressure washer surging can vary, the issue often stems from restricted water flow. 

To resolve surging, all hoses should first be inspected to ensure they are free of kinks, leaks, or blockages. All hoses and fittings must be connected properly, and the faucet or spigot should be opened to full force. Additionally, the spray wand should be set to the high-pressure setting. 

Debris should also be cleared from the nozzle. Even a small amount of dirt in the tip can cause enough obstruction to make the pressure washer pulsate. If the unit included a nozzle cleaner, it should be used to clean the tip; otherwise, a small pin or paper clip can effectively clear any lodged debris. 

If the pressure continues to fluctuate after these checks, air may be trapped in the pump. To re-prime the pump and remove the air, the machine should be turned off and the high-pressure hose and trigger gun disconnected. With only the garden hose attached, the water source should be turned on to allow water to flow through the pump for 20 to 30 seconds. Finally, the water should be turned off so the high-pressure hose and trigger gun can be reconnected for another test. 

Why Should a Pressure Washer Be Turned Off When Not In Use? 

If a pressure washer is left running without the trigger being pulled, water remains trapped inside the pump. This stationary water continues to heat up and can eventually melt the pump seals. Furthermore, as the pump temperature rises, pulling the trigger introduces cold water into a very hot system, which can lead to pump cavitation. 

While some pumps are equipped with a bypass hose to recirculate and cool the water, the unit should still not be left idling for extended periods. 

It is best to always turn the pressure washer off when it is not actively in use. If a pressure washer fails to work or keeps shutting off, overheating during idling may be a contributing cause of the issue. 

Can You Connect Different Diameter Hoses Together? 

Pressure washer hoses with different diameters can be connected, provided the connections are compatible. Because quick-connect fittings are standardized for both 1/4" and 3/8" hoses, they can be joined using the appropriate couplers. 

It is generally suggested to have the smallest diameter hose connected directly to the pump, moving from a smaller to a larger diameter to avoid restricting water flow. Additionally, when a pressure washer hose is replaced, it is essential to ensure the new component is specifically rated as a high-pressure hose. 

Can You Repair a Leaking Pressure Washer Hose 

No, a leaking pressure washer hose should never be patched or repaired. 

Pressure washer replacement hoses are carefully engineered to distribute pressure evenly throughout their entire length. They use specially designed wire mesh to maintain shape and multiple layers of material designed to withstand high pressure. 

Once these layers are compromised, a new high-pressure hose must be purchased to ensure the equipment can continue to be used safely. 

How Does a Hot Water Pressure Washer Work? 

The differences between hot and cold pressure washers can often be confusing. It is a common misconception that the burner is a storage tank or that water is heated before it enters the pump. In reality, hot-water pressure washers can be used as cold-water machines as well. 

The large metal cylinder on these units is not a water storage tank, but rather the burner that heats the water as it passes through. Because the water passes through the pump before it is heated, the pump itself does not need to be rated for high temperatures. However, the hose, spray gun, and lance must be specifically rated for hot water use. 

A hot water machine operates identically to a cold water machine until the water exits the pump. In a cold water pressure washer, water travels directly from the pump to the high-pressure hose and the gun. In a hot water pressure washer, the water exits the pump and passes through a heating element before reaching the hose and gun. 

Why Can't a Direct-Drive Pressure Washer Pull Water from a Tank? 

Questions often arise regarding whether water can be pulled from a tank into a direct-drive pressure washer. While belt-driven pressure washers are gravity-fed from a tank, direct-drive pumps operate differently. Because direct-drive pumps spin at significantly higher RPM than belt-drive models, they cannot pull water on their own. 

How to Winterize a Pressure Washer 

Whenever a pressure washer is not in use for more than 30 days, the storage steps described in this article are recommended. 

Essentially, the process involves stabilizing the fuel if it is to remain in the unit, flushing all water out of the machine, and adding a pump-saver. This prevents the pump from freezing or building up internal moisture during storage. 

How to Change the Oil on a Pressure Washer Pump and Engine 

The pump and engine oil levels should always be checked before using the machine. Both the pump and engine oil require periodic changes, except for axial pumps, which are sealed and do not require oil level checks. 

If difficulty arises when checking oil levels, it is suggested to use a flashlight and move to eye level with the sight glass, as the level is harder to discern from above. If bending down is difficult, a photograph of the sight glass can be taken with a phone for closer inspection. Additionally, lightly rocking the machine can help make the motion of the oil visible inside the pump. 

Triplex pumps feature a sight glass for monitoring oil levels, which should ideally be centered on the red dot. The engine oil is checked using the engine's dipstick. 

Rather than simply adding more oil, the oil should be drained and replaced entirely. The process for checking the pump oil is similar to checking a vehicle's oil: the dipstick is removed, wiped clean, then reinserted to verify that the oil reaches the correct level. 

Oil Change Intervals: 

• Engine Oil: Should be changed after the first 20 hours of use or the first month, whichever occurs sooner. Following the initial change, the engine oil should be replaced every 6 months or 100 hours of use. 
• Standard Pump Oil: Should be changed after the first 50 hours of use. Subsequent changes should occur every 100 hours of use or every 3 months. 
• Cat Branded Pumps: These units have specific intervals. If Cat brand pump oil is used, changes are required every 500 hours. If other oil brands are used in a Cat pump, the oil must be changed every 300 hours. 

What Type of Oil Does My Pressure Washer Take? 

The essential requirement for pump oil is that it must be non-detergent and non-foaming. The appropriate engine oil for a pressure washer is always specified in the owner's manual based on the manufacturer's recommendations, with SAE 10W-30 being the standard for most units. 

Depending on the temperature range in which the machine will be operated, 10W-30, 10W-40, or synthetic 5W-30 may also be used. Synthetic SAE 10W-30 is frequently recommended as it covers the widest temperature range and performs well in all conditions. 

The proper oil for a pressure washer pump is also specified by the manufacturer, typically within the owner's manual. Recommendations vary by brand: 

• Cat Branded Pumps: Use of Cat premium-grade hydraulic oil (ISO-68) is suggested. While other oils may be used, doing so will alter the required oil change interval. 
• Simpson: The use of Simpson Premium pump crankcase oil or SAE 15W-40 is recommended. 
• Karcher & General Pumps: These manufacturers recommend SAE 15W-40. 

How Do You Replace a Pressure Washer Plug? 

Every pressure washer pump is equipped with a type of vented oil plug designed to keep the oil contained within the pump. Many General Pumps feature an oil plug that includes a dipstick for checking oil levels. 

Cat pumps are typically shipped with a sealed plug inserted, which must be replaced upon arrival. If a pressure washer were shipped with a vented plug, a significant amount of oil could leak out during transit. Consequently, most models ship with a threaded sealed plug that must be unscrewed and replaced with a vented plug before the machine is operated. 

Depending on shipping methods, various components of the pressure washer may become covered in oil, which can cause operational issues if not addressed. An oil-soaked air filter is the most frequent problem, though oil on the spark plug can also occur. In these instances, the air filter and spark plug must be removed, wiped clean, and dried. 

Once the spark plug is removed, the recoil should be pulled to clear any excess oil from the system. This step can be messy and should be performed in an area where oil spray will not cause damage or stains, such as on grass. When oil no longer emerges from the spark plug port, the unit can be reassembled. After a final check of the oil levels, the pressure washer is ready for use. 

Why is My Pressure Washer Smoking? 

Observing a pressure washer emitting smoke can be startling. However, white smoke is most often simply residual oil burning off a component of the engine. There is generally no way to stop or prevent this occurrence; it does not cause damage to the engine and typically only happens during the initial startup. 

If the pressure washer continues to smoke after the first use, if the smoke turns black, or if the unit continues to shut itself off, a different mechanical issue may be present. In these cases, it is recommended to consult other troubleshooting resources regarding proper startup procedures or how to address persistent cycling, surging, or stalling. 

Why is it Important for Nozzles to be Sized Correctly for GPM and PSI Requirements? 

If nozzles are not sized correctly for the pressure washer’s specific PSI and GPM requirements, the machine will not perform as intended. An orifice size that is too small will restrict water flow, potentially straining the pump, while an orifice that is too large will result in a lower PSI output than desired. 

It is essential to consult a nozzle sizing chart to determine the correct orifice size for a specific unit. When a pump is replaced or upgraded to one with different pressure or flow ratings, the required orifice size may change. To ensure the safe and effective operation of the pressure washer, spray tips must be resized whenever the pump's specifications are altered. 

What Is More Important, Flow (GPM) or Pressure (PSI)? 

The choice between PSI (Pounds per Square Inch) and GPM (Gallons per Minute) depends entirely on the specific application. For stubborn or deeply embedded dirt, a higher PSI is generally more important. However, for washing away large volumes of debris or cleaning expansive areas, higher GPM is more effective. 

When choosing between the two, it is generally recommended to prioritize GPM. While a user can increase effective pressure by changing spray tips or moving the wand closer to the surface, the water flow (GPM) is a fixed capacity of the pump and cannot be increased. It should also be noted that higher PSI increases the risk of surface damage. 

Because different surfaces have varying tolerance levels, it is important to adhere to the recommended pressure ratings for the material being cleaned.