Find the Right Pressure Washer Replacement Pump in 3 Steps
So you have to get a new pump for your pressure washer. No big deal—there are plenty of pumps available on the market.
But pressure washer pumps aren’t interchangeable, and getting the wrong one can cause all sorts of problems for you and for your washer. So how do you find one that is compatible with your unit?
Finding the right replacement pump for your pressure washer comes down to three things:
- Engine shaft size and orientation
- Bolt pattern
- Engine horsepower
We’ll walk you through these factors so you can get a new pump that fits perfectly. There’s also a fitment chart at the bottom of the page to provide you with more information that even has clickable links to our pumps.
Plus, once you have your pump, check out our video on how to install it in your pressure washer.
Ready to find your new pressure washer pump? Let’s get started.
Pro tip: before removing your old pump, make a note of the orientation of your engine shaft and whether the water inlet and outlet face the front or rear of your pressure washer. You can make this even easier by taking a few pictures of your equipment before you start.
Step 1: Determine Engine Shaft Size and Orientation
Remove your old pump and take a good look at the engine shaft. Put a micrometer on it and get an accurate measurement; don’t just eyeball it. This is a crucial starting point for making sure you get the correct replacement pump.
Most pressure washer engines have a shaft measuring 3/4”, 7/8”, or 1” in diameter.
Then take note of whether your engine is vertical or horizontal. Does the engine shaft point straight up/down (vertical), or does it point out to the side (horizontal)?
Some replacement pumps can only be installed on a horizontal engine shaft due to an oil ventilation port, so double-check our chart before making your decision.
Step 2: Verify Bolt Pattern
Next, measure the bolt pattern around the shaft, going from the center of one bolt hole to the center of the next.
A few power washer models might have two—or even three—different bolt patterns around the engine shaft. The most common bolt patterns are the following:
- (4 bolts) 2 9/16” square
- (4 bolts) 2 5/8” square
- (3 bolts) 7 11/16", 6 3/16", 6 7/16"
- (4 bolts) 5 1/4", 3 1/4", 5 3/16", 4 1/2"
Keep in mind that if your bolt pattern does measure 2 9/16” square, a pump with a bolt pattern of 2 5/8” square will still work for you.
Also, if you have a vertical engine shaft and a three-bolt mounting pattern, note which direction your water inlet and outlet face. If they come out of the front of your washer, you’ll need a front-facing replacement pump, and if they come out of the back of your washer, you’ll need a rear-facing one.
You can use our chart below to make sure you’re looking at pumps with the water connections oriented in the direction you’ll need.
Step 3: Check Engine Horsepower (HP)
Now that you know your engine shaft size, orientation, and bolt pattern, you should have an idea of which pumps are going to work for your pressure washer.
Some models might have as many as six replacement pump options. However, not every pump will necessarily be right for your engine.
A common issue is getting a pump with a maximum PSI that's too high given the horsepower of your engine. If this is the case, the pump can produce too much pressure for your engine to handle, causing it to bog down or even stall.
It’s also possible to swing too far the other way and get a pump with too low of a PSI for your engine’s horsepower. If this happens, the engine could wind up damaging your pump over time. However, we find that this is a less typical scenario.
We've provided some guidelines to help you match your engine's horsepower to your pump's PSI. Find your engine’s maximum horsepower rating to get the recommended PSI in the chart below:
6.5 HP = 3600 max PSI or less
6 HP = 3100 max PSI or less
5.5 HP = 2800 max PSI or less
5 HP = 2600 max PSI or less
4.5 HP = 2400 max PSI or less
For heavy-duty pressure washers, you can find more HP to PSI details in the chart at the bottom of the page.
Wrapping up
With these three factors sorted out, you’ll be able to find a replacement pump that works with your pressure washer. If you need help finding the right pump on our site, contact our customer service team, and we’ll help you out.
What about when it’s time to actually replace the pump on your pressure washer? We’ve got you covered there, too. After you’ve received your new pump, go ahead and watch our installation video, which will show you how to remove your old pump and put on the new one.
Plus, if you have problems with your pressure washer even after you switch out your pump, check out this helpful Rugged U video on troubleshooting pressure washer issues. You can also read our pressure washer troubleshooting blogs. We offer one blog on troubleshooting your overall unit and one that focuses on issues with your pressure washer's pump.
Finally, read our list of tips for DIY pressure washing so you're ready to go once your pressure washer is running again.
The ROP Shop's pressure washer pump chart
Not showing up? You can also get the chart here.
WRITTEN BY: KATE HUFFMAN [EDITED 2/2023]
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Installing a new pressure washer pump doesn’t have to be a hassle. Let The ROP Shop walk you through it.