Important Things You Need To Know About Replacement Water Pressure Water Pump

By | July 18, 2018

If you start your pressure washers and it doesn’t pressurize water, you don’t have to dispose it. If it starts up but doesn’t spray pressurized water, chances are that the pump is not working. In this case, a replacement pressure washer pump is a much better and affordable option than replacing the whole pressure washer.

Nearly all entry-level pressure washers come with wobble pumps which cannot be replaced. That means that you are better off getting a whole new unit, but the best electric and gas units come with triplex plunger or axial cam pumps that can be replaced.

How to choose the right water pressure replacement pump

·         Do your research

First and most importantly, you will want to make sure that you buy a replacement pump that is compatible with your machine. In order to do this correctly, you will need to do a couple of things

You need to know whether your pressure washer pump is triplex or axial. You can easily determine this by looking at how the pump attaches to the motor. For an axial cam, the driveshaft of the motor points to the brass valves directly. This means that the driveshaft directly spins the cylinders that play the significant role of pressurizing the water.

For a triplex pump, the driveshaft usually runs parallel to the brass valves. This basically means that the driveshaft powers the crankshaft which moves the plunger rods that play the significant role of pressurizing the water.

The next step is determining the diameter of the shaft. You also need to know whether it is hollow or solid. Look at how the flange attaches to the motor and also measure the pattern of the bold. The goal is to ensure that the new pump installs as-is.

You also need to determine if the current motor is vertically or horizontally shifted. In short, is the pump mounted next the engine (which will now be horizontal) or underneath (which will now be vertical).

·         Match it

You will also want to match your pump’s pressure rating and gallons per minute with those of the replacement you want to make. One thing you should always keep in mind is that more is usually not better. Buying a new pump that can put out more PSI can either be too powerful for the burst rating of your hose or bog down the engine.

You need to check out installation drawings as well as owner’s manuals for similar replacement pumps and compare the measurements to ensure that your pump fits properly. Basically, all top engine manufacturers produce mounting flanges with the same specs and measurements.

It is however important to double-check the measurements before you make your order.

How to replace your pressure water pump

The role of the pressure water pump is to create water pressure which comes out from the nozzle. Detergent residue in the pump and air in the inlet water supply is likely to damage the pump.

If the pressure at the nozzle is low because of a damaged pump, you will want to replace the pump. Before you begin replacing the pump, you need to wear gloves to protect your hands and allow the pump and engine to cool.

Tools required

  • Allen head bit set
  • Wrench set
  • Gloves
  • Pipe thread sealing tape

NOTE:  Repairing your appliances can be hazardous. You also need to use proper safety equipment and tools and follow all the instructions in the guide. Don’t proceed with the replacement until you are confident that you have understood the steps. Some repairs should be done only by qualified technician.

1.      Disconnect the spark plug wire

The first step is disconnecting the spark plug wire

2.      Disconnect hoses that have been attached to the pressure pump

Find the inlet water hose and remove it from the pump and then remove the nozzle hose. Place the chemical injection tube in case the tube has some fluid in it. Then pull off the chemical injection inlet valve.

3.      Remove the pump

The next step is removing the pump which is usually attached at the bottom of the machine by bolts. Simply loosen the mounting bolts that secure the pressure [ump to the engine, but don’t remove them.

Support the bottom of pump with the pressure washer in an upright position as you remove the mounting bolts. Pull off the pump from the engine crankshaft to remove the pressure pump from the engine.

4.      Prepare your new water pressure pump for installation

Take the thermal relief valve from the old pump and transfer it t the new one. Seal the thermal relief connection vale using a pipe thread sealing tape.

5.      Install the new pressure pump

Align the pump correctly on the engine crankshaft and then slide it onto the crankshaft. You will also have to rotate the pump so that it aligns with the mounting holes. Reinstall the mounting bolts and tighten them.

6.      Reconnect the houses to the water pressure pump

Now that you have positioned the water pressure pump correctly and bolted it onto the engine, the next step will be reconnecting the chemical injection tube on its position. If you have used a hose clamp on the chemical injection hose, remove it. Reconnect the nozzle hose and inlet water hose on the pump.

7.      Record the spark plug

You will now need to reconnect the spark plug wire

8.      Test your new pump

Start your pressure washer to test the newly installed pump.

Installing a replacement pressure washer pump should take less than 30 minutes. But as we have mentioned above, you have to be confident that you can do this. If not, you will want to seek the help of a professional.


Whenever you are experiencing a problem with your water pressure pump and you want to replace it, you will want to choose the right pump. You want to make sure that you are choosing a pump that will fit properly and work efficiently with the engine. Most importantly, you need to install it properly so that it functions as it should.