Pressure washer pump guide: Repair and replacement

Pressure washer pumps are crucial for enhancing the cleaning efficiency of your pressure washer system. Understanding how to maintain and troubleshoot these pumps can save you time and money. Follow this guide to identify and fix common pump issues.

Understanding Pressure Washer Pumps

The first step is to understand the pressure washer pump you need to repair or replace. Each type is designed to handle specific psi (pounds per square inch) and volume levels, making it crucial to choose the right pump for your pressure washer's requirements.

Wobble Plate Pump

Wobble plate pumps are entry-level pumps often found in consumer-grade pressure washers. This pump type uses a wobble plate connected to the drive shaft to push pistons back and forth, creating the pressure needed to pump water. The plate 'wobbles' as it spins, which is where the name comes from.


Wobble plate pumps typically operate at lower psi and gallons per minute (GPM) ratings, suitable for light-duty tasks. These pumps generally handle about 2000 psi or less.


Since the wobble plate causes significant wear on its pistons due to the angle of operation, these pumps have a relatively short lifespan compared to other types. They are not designed for heavy or frequent use.

Axial Cam Pump

Axial cam pumps are more robust than wobble plate pumps and are commonly found in medium-duty pressure washers. In this design, the cam and pistons move in a parallel direction to the drive shaft. As the shaft spins, the cam pushes the pistons back and forth in a straight line, which compresses water and builds pressure.


These pumps can handle moderate pressure levels, usually up to around 3500 psi, making them suitable for more frequent use than wobble plate pumps. They offer a good balance of performance and affordability for most homeowners.


Axial cam pumps are more durable than wobble plate pumps but still have limitations due to the fixed angle of the cam, which leads to faster wear and tear than triplex pumps. However, they are easier to maintain than wobble plate pumps and can offer several years of service with proper care.

Triplex Plunger Pump

Triplex plunger pumps are the most durable and efficient of the three types. They feature three plungers moving back and forth in cylinders, driven directly by the crankshaft. This direct drive creates a consistent, high-pressure flow of water.


Triplex pumps are capable of handling high psi and GPM ratings, often used in commercial and industrial pressure washers. These pumps can manage pressures exceeding 3000 psi and are suitable for heavy-duty cleaning tasks.


The design of triplex plunger pumps allows for less wear and tear since the plungers move in a more efficient, straightforward motion compared to the angled movements in wobble and axial pumps. This efficiency not only extends the lifespan of the pump but also supports more frequent and intensive use. Triplex pumps are typically rebuildable, meaning specific worn-out parts can be replaced, which can significantly extend their life.

Which one is best? For occasional, light cleaning, choose a wobble plate pump. For regular home use, an axial cam pump offers a good mix of performance and longevity. However, for frequent or industrial use requiring high power and reliability, a triplex plunger pump is the best choice. Each type supports different psi and volume levels, which should align with the tasks you expect to tackle.

Now, it's time to know the signals of a faulty pressure washer pump.

Signs that your Pressure Washer Pump is Faulty

Recognizing the early signs of a faulty pressure washer pump can prevent more significant issues. Here are the common indicators to watch for:

  • Reduced pressure: A faulty unloader, worn or damaged valves, or a clogged nozzle could all be to blame for a noticeable pressure drop. If your pressure washer isn't delivering the expected level of psi, it's a sign that something's not right within the pump.

  • Unusual noises: Listen for grinding, knocking, or squealing sounds from your pressure washer. These noises often indicate that internal components like bearings or pistons are failing.

  • Leaks: Water or oil leaking around the pump is a telltale sign of seal or gasket failure. Regular inspections can catch leaks early, preventing further damage and maintaining optimal performance.

  • Overheating: If the pump often overheats, this may be due to a low water supply or a malfunctioning thermal relief valve. Overheating can quickly lead to pump failure, so it’s crucial to address this issue promptly.

Step-by-step Fault Diagnosis

To diagnose and potentially fix issues with your pressure washer pump, follow these steps:

  1. Visual inspection: Begin with a thorough visual inspection of the pump. Check for any obvious signs of damage like cracks in the pump housing or broken fittings. Make sure the water inlet is free of debris.

  2. Check the pump oil: Inspect the pump oil level and quality. Milky or cloudy oil can indicate water contamination, which is harmful to the internal parts of the pump. Change the oil if it's not clear.

  3. Examine valves and seals: Dismantle the pump to inspect the valves and seals. Replace any worn or damaged valves to ensure they can handle the required pressure levels. Check the seals for wear and replace them if necessary to prevent leaks.

  4. Perform a pressure test: Attach a pressure gauge to the outlet of the pump and monitor the pressure as the pump operates. Fluctuating pressure levels can indicate a problem with the pump’s unloader valve or its internal components.

  5. Consult the manual: Refer to your pressure washer’s manual for specific troubleshooting tips related to your model. This can provide additional guidance on what to check based on the symptoms you're experiencing.

If your pressure washer pump is over 10 years old, it may be wiser to replace it. Obsolete parts in an older pump can be challenging to find. If the replacement will cost more than half the value of a new pump, it's better to replace it. Fortunately, Hotsy Water Blast carries an extensive inventory of cold and hot water pressure washer pumps.

Pressure Washer Pump Maintenance

Maintaining your pressure washer pump regularly is crucial for extending its life and ensuring optimal performance. Conduct routine inspections to check for any signs of wear or damage. Catching issues early helps prevent them from leading to more significant problems. After each use, make sure to clean and dry your pump thoroughly. Proper storage is also essential; store your pressure washer in a cool, dry place to avoid rust and corrosion. In colder climates, it's important to winterize the pump by flushing out any water to prevent freezing and cracking.

Always use clean, debris-free water in your pressure washer. Dirt and sediment can clog and damage the internal components of the pump, leading to inefficiencies or breakdowns. Regularly changing the pump oil is another critical maintenance step. Keeping the oil fresh and at the correct level prevents mechanical wear and overheating, common causes of pump failures. Additionally, keep an eye on the condition of all moving parts, such as hoses, nozzles, and o-rings, and replace them as they wear out to maintain your pressure washer in top condition. By following these maintenance practices, you can ensure that your pressure washer pump continues to operate efficiently for all your cleaning needs.


Has your pressure washer pump seen better days? For repair or replacement, look no further than Hotsy Water Blast. Whether you have an electric, diesel, or gasoline pressure washer, our in-house and mobile technicians repair and maintain all makes and models of pressure washer pumps. We also offer a pre-scheduled maintenance program to protect your equipment and investment.

Contact us today for more information.