Pressure Washer Pumps

How to Choose the Right Pressure Washer Pump

Pump choice is where contractors either set themselves up for years of reliable work or buy a machine that lives in the shop. Flow rate and pressure rating come first, since those numbers have to match the work. Drive type (direct or belt) decides how long the pump will hold up under your hours. And brand matters because when a seal blows, you need to know you can get the part by Tuesday.

Match GPM and PSI to the work

Pressure breaks dirt loose. Gallons-per-minute is what moves it off the surface. A 4,200 PSI / 3 GPM pump cleans slower than a 3,000 PSI / 5.5 GPM pump on the same flatwork. For residential side work, 4-5 GPM is enough. For full-time commercial flatwork (driveways, sidewalks, fleet lots), target 5.5+ GPM and let PSI follow. Pumps are rated for a max PSI and a max GPM, and running past either spec is what kills seals.

Direct drive vs belt drive

Direct-drive pumps bolt straight to the engine shaft and spin at 3,400 RPM. They're lighter, cheaper, and have fewer parts to fail, which makes them a good fit for under 20 hours a week of use. Belt-drive pumps run at around 1,450 RPM through a pulley system. They cost more, need belt service, and take up more space, but they run cooler and last roughly twice as long under daily commercial duty. If you're running more than four hours a day, belt drive pays for itself in pump life.

Brand and parts availability

We carry Comet, CAT, and General Pump because those are the brands you can actually source replacement seals, packings, and check valves for at any pressure washer supply house in the country. Cheaper imported pumps may save you $200 up front, then strand you for a week waiting on a $30 seal kit. Comet and General Pump sit at similar specs and price points, and their RW/FW-series and PSS-series are interchangeable on most BE machines. CAT pumps cost more but typically outlast the rest under hard use.

Pressure Washer Pump Sizing Chart

Related Categories

• Complete Pressure Washers
• Comet Pumps & Parts
• General Pump
• Pump Repair Kits
• Pressure Washer Pump Oil
• All Pressure Washing Equipment

Frequently Asked Questions

What pressure washer pump do I need for my machine?

Match the pump's max PSI and GPM to your engine's horsepower, and match the pump's shaft to the engine shaft (¾" hollow shaft for a GX200, 1" hollow shaft for a GX270/GX390 on direct-drive setups, keyed shaft for belt drive). A Honda GX390 (11.7 HP) drives pumps up to about 5.5 GPM. For 8+ GPM you need a GX690 or equivalent V-twin. Undersize the engine and it'll bog and overheat under load. Oversize the pump and the engine can't spin it to spec.

What's the difference between direct drive and belt drive pumps?

Direct drive bolts the pump to the engine and spins it at 3,400 RPM. Simpler, cheaper, and lighter, but harder on seals over time. Belt drive uses pulleys to spin the pump at around 1,450 RPM, running cooler and longer. Direct drive is fine for under 20 hours a week of use. Belt drive is what you want for daily commercial work, and it typically delivers roughly twice the service life.

Which is best: Comet, General Pump, or CAT?

Comet and General Pump are nearly interchangeable at the residential and light-commercial level. The Comet RW5535 and General Pump PSS5535 hit the same 3,000 PSI / 5.5 GPM spec at the same price, and parts are easy to source for both. CAT pumps cost more up front but are the go-to for high-duty commercial rigs where pump life matters more than initial cost. For most contractors, the right answer is "whichever one your local supplier stocks parts for."

How long should a pressure washer pump last?

Pump life depends more on maintenance than on the badge. A direct-drive triplex under daily commercial use will need a rebuild well before a belt-drive setup running the same hours, and our shop experience and oil-consumption records both point to belt drive lasting roughly twice as long. The biggest factors are oil change discipline (use non-detergent pump oil and stay on the schedule), keeping debris out of the inlet with a filter, and never running the pump dry in bypass for more than a couple of minutes.

Can I replace just the pump and keep my engine?

Yes. That's the most common rebuild path. Pumps almost always fail before engines do, especially on Honda-powered rigs. Match the replacement pump's shaft size and bolt pattern to your engine, and verify the PSI/GPM rating doesn't exceed what your engine can drive. A 5.5 GPM pump swap onto a GX390 is a straightforward job for an experienced tech. Bigger jumps in flow rate may require an engine upgrade too.

Do these pumps include an unloader?

Check the listing, since some include an unloader and some don't. Every triplex pressure washer pump needs an unloader to reroute water through a bypass loop when you let off the trigger, or pressure spikes inside the pump and destroys the seals. If your replacement pump doesn't include one, pair it with a K7, VRT3, or VRT100 sized to your pump's max GPM. The K7 and VRT3 cover most rigs up to 10 GPM. The VRT100 handles 1/2"-port high-flow setups.