The Comet P40 Soft Wash Pump moves up to 11 GPM at 300 PSI through three diaphragms, so it pumps SH all day without corroding. You get the pump head, a 3/4" solid-shaft gearbox, and an adjustable regulator. No engine.
Key Features
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Three-diaphragm design: Pumps SH and surfactant without the corrosion that kills brass and steel plunger pumps. The diaphragms keep chemical off the drive train.
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Up to 11 GPM: High flow at low pressure throws solution to roof and second-story height. This is a soft wash pump, not a high-pressure washer.
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Desmopan diaphragms: Rated for sodium hypochlorite and the other aggressive chemicals soft washing runs.
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Poly and 316 stainless wet parts: No brass in the chemical path. The whole wetted side is built to live in bleach.
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Single-piece manifold (2025 design): Fewer leak points and quicker service than the older multi-piece layout, with a bolt-on regulator and aluminum head plates.
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3/4" gearbox and adjustable regulator: Bolts to a 5 to 6.5 HP horizontal-shaft engine and dials pressure where you want it. Built-in gauge port.
Specifications
| Pump type |
3-diaphragm, semi-hydraulic |
| Max flow |
Up to 11 GPM |
| Max pressure |
Up to 300 PSI (low-pressure, high-flow) |
| Max RPM |
550 |
| Inlet / outlet |
1" inlet, 3/4" outlet |
| Diaphragm material |
Desmopan, rated for SH |
| Wet parts |
Polypropylene manifold, 316 stainless check valves |
| Drive |
3/4" solid-shaft gearbox (fits 5 to 6.5 HP engines) |
| Pump oil capacity |
30.4 fl oz |
| Max fluid temp |
140°F |
| Weight |
About 40 lb (pump, gearbox, regulator; no engine) |
| Origin |
Made in Italy |
What's Included
- Comet P40 pump head
- 3/4" solid-shaft gearbox
- Adjustable pressure regulator
- Built-in gauge port (offered with or without an installed gauge)
No engine. The complete gas sprayer and the full soft wash bundle are separate products. The pump bolts to a Honda GX160, GX200, or similar 5 to 6.5 HP horizontal-shaft engine through the 3/4" gearbox, and the current model also runs on an electric-motor setup. It plumbs into a soft wash proportioner or metering block with 1" valves, 5/8" or 1/2" SH-rated soft wash hose, chem tanks, and a hose reel. It's a low-pressure pump at 300 PSI. It isn't for surface cleaners or 4000 PSI pressure-washing work, and it isn't rated for solvents or acids.
How It Works
Three diaphragms flex in an oil bath, driven by a connecting-rod mechanism. The diaphragms physically separate the chemical from the drive train and crankcase oil, so SH only ever touches the polypropylene manifold, the 316 stainless valves, and the diaphragm face. That's why it survives bleach where a piston pump's brass and steel wet parts corrode and fail. The pump self-primes, draws your mixed solution from the tank or proportioner, and pushes high flow at low pressure out to the reel and gun.
Flush it with fresh water for at least 5 minutes after every job. Never leave SH sitting in the pump, never run it dry, and don't hold it in bypass longer than 60 seconds.
Pairs Well With
Frequently Asked Questions
How many GPM is the Comet P40?
Up to 11 GPM at 300 PSI. That's high flow at low pressure, which is what soft washing needs to throw solution up to roof and second-story height. It's a diaphragm pump, not a high-pressure washer.
Will the Comet P40 handle 12.5% SH?
Yes. The wet parts are polypropylene, 316 stainless, and Desmopan diaphragms, all rated for sodium hypochlorite. Flush with fresh water for at least 5 minutes after every job and never leave SH sitting in the pump.
Gas Comet P40 or a 12V pump for soft washing?
The gas P40 gives higher flow, around 11 GPM, with longer reach and longer service life for big and commercial jobs. A 12V pump runs 5.3 or 7 GPM, quieter and cheaper, and makes sense for part-time or lower-volume residential work. The P40 is the pump you grow into.
