What Type of Pump Do I Have?
First, you'll need to make sure the replacement pump you're buying will be compatible with your current machine. To do this, you'll need to know if the existing pressure washer pump is axial or triplex.
Determine if your existing motor is horizontal or vertically shafted—Does your pump mount next to the engine (connected to a horizontal driveshaft) or underneath (connected to a vertical driveshaft)?
Check PSI & GPM
While you're in the process of shopping around for a replacement pump, remember that there's no need for the replacement pump to be of the same brand as your existing pressure washer pump. It can be another brand. You have the option of choosing any brand of replacement pump as long as it has the same GPM (Gallons per Minute) and PSI (Pounds per Square Inch) rating as your existing pump. Remember, more is not always better—getting a new pump that puts out a lot more PSI can either bog down the engine, or be too powerful for your hose's burst rating.
Usually, the description will tell the hp range and cc range, what you need to do is check whether your machine is within the range
When you are replacing a pressure washer pump, you need to make sure that the bolt pattern and mounting direction match perfectly. You’ll see that replacing a pressure washer pump is as easy and as simple as removing a few mounting bolts.
Now that you've found the perfect replacement pump, it's time to install it and get back to washing.