Home Pressure Washer Gun Guide
Spray-gun compatibility
Pressure Washer Gun Guide: Replacement, Fittings & Ratings
A pressure washer gun must match the high-pressure hose on one side and the wand or accessory on the other. Check both connections plus pressure, flow and temperature before treating a replacement gun as compatible.
A gun has two interfaces
High-pressure hose → gun inlet → trigger valve → gun outlet → wand/accessory. Verify both ends plus PSI, GPM and temperature.
Technical examples reviewed: August 28, 2026.
Start with the inlet and outlet—not the handle shape
The spray gun is the control valve between the high-pressure hose and the wand or accessory. Replacement-gun listings often emphasize PSI, but a practical match requires at least five separate checks.
Common pressure washer gun connection layouts
There is no single universal layout. Current manufacturer examples span residential M22-to-M22 guns, professional threaded-port guns and professional quick-connect configurations.
| Current example | Pressure / flow | Temperature | Published inlet | Published outlet |
|---|---|---|---|---|
| SIMPSON 80147 | 3400 PSI / 8.0 GPM | 140°F | M22 male | M22 female |
| SIMPSON 80148 | 4500 PSI / 6.6–8.0 GPM* | 140°F | M22 male with adapter | M22 female |
| SIMPSON 80178 | 5075 PSI / 12.0 GPM | 212°F | 3/8" FNPT, adapters included | 1/4" FNPT |
| MTM Hydro SG28 | 4000 PSI / 12 GPM | 320°F max | 3/8" female | 1/4" female |
| MTM Hydro SGS28 configured gun | 4000 PSI / 12 GPM | 320°F max | 3/8" QC plug | 1/4" QC coupler |
*SIMPSON's current 80148 page is internally inconsistent on flow: its feature/compatibility text and 2026 catalog state 6.6 GPM, while the page's product-spec block shows 8.0 GPM. Verify the current manufacturer rating before using it in a higher-flow system. The fittings installed on any gun can also change how the underlying ports are presented.
M22 gun systems vs. 3/8-inch / 1/4-inch quick-connect systems
Residential M22 pattern
Many consumer hoses and replacement guns connect through M22 threads. SIMPSON's 80148, for example, uses M22 connections and includes a threaded M22 QC hose adapter.
Verify the M22 14 mm vs. 15 mm subtype where it applies.
Professional QC pattern
Professional guns often use a 3/8-inch hose-side connection and 1/4-inch accessory-side connection. MTM's configured SGS28 is one current example with a 3/8-inch plug inlet and 1/4-inch coupler outlet.
Brand-specific gun paths: RYOBI · SIMPSON · Kärcher · CRAFTSMAN · DEWALT · Greenworks · Sun Joe · Generac · Troy-Bilt.
Standard-length gun vs. short pressure washer gun
A short gun places the accessory closer to the trigger hand and can make compact work easier, particularly with foam cannons or vehicle-cleaning accessories. A traditional gun plus wand provides more separation between the operator and the spray point and is the normal configuration for general cleaning.
That is a usability choice, not a compatibility shortcut. A short gun still needs the correct hose inlet, accessory outlet and pressure/flow/temperature ratings. If the machine uses a proprietary gun/wand assembly, an adapter may be required—or the system may not support the desired conversion.
Hot-water vs. cold-water spray guns
Temperature can be the hidden mismatch. SIMPSON's current 80148 is a cold-water gun rated to 140°F, while the 80178 professional gun is documented for hot and cold water up to 212°F. MTM's SG28 family publishes an even higher maximum temperature for the gun itself.
The complete pressure-washer path must still respect the lowest applicable temperature rating among the hose, adapters, gun, wand and accessory.
Trigger safety is part of the selection
Current SIMPSON replacement guns include a safety lockout. Follow the equipment instructions: secure connections, use the trigger lock when finished spraying, shut down and depressurize before removing accessories, and never point the high-pressure stream at people or animals.
Replacement-gun checklist
| Check | Record | Common mistake |
|---|---|---|
| Hose inlet | Exact thread/QC family, size and gender | Buying “M22” without checking the subtype or installed adapter. |
| Wand/accessory outlet | Exact thread/QC family, size and gender | Assuming every gun ends in a 1/4-inch QC. |
| PSI / GPM | Machine rating and gun maximums | Looking only at PSI. |
| Temperature | Cold/hot-water requirement | Using a cold-water gun in a hot-water system. |
| Installed adapters | What is removable vs. integral | Confusing an adapter's connection with the gun body's base port. |
After the inlet, outlet and ratings are established
Compare replacement spray guns only within the connection and operating class you identified. Re-check whether listings include adapters or show the bare gun ports before ordering.
Technical sources
- SIMPSON — 2026 Industrial Catalog — current 80147/80148/80178 gun connection, pressure, flow and temperature table.
- SIMPSON — Spray Gun 80148 — current M22 connections, 4500 PSI, 140°F and safety-lockout details; page currently contains conflicting 6.6 vs. 8.0 GPM values.
- SIMPSON — Professional Spray Gun 80178 — 3/8-inch FNPT inlet, 1/4-inch FNPT outlet, 5075 PSI, 12 GPM and 212°F.
- MTM Hydro — SG28 — 3/8-inch inlet, 1/4-inch outlet, 4000 PSI, 12 GPM and 320°F maximum.
- MTM Hydro — SGS28 configured spray gun — current 3/8-inch QC plug inlet and 1/4-inch QC coupler outlet example.
Frequently asked questions
Are pressure washer guns universal?
No. Many replacement spray guns use common M22, 3/8-inch or 1/4-inch connections, but inlet/outlet configuration, pressure, flow, temperature and proprietary interfaces vary. Match both ends and all operating ratings.
What fittings are common on a pressure washer spray gun?
Residential replacement guns often use M22 threaded hose and wand connections. Professional guns are commonly configured with a 3/8-inch inlet and 1/4-inch outlet, sometimes through quick-connect fittings or threaded FNPT ports. The exact gun specification controls.
Can I use a higher-PSI replacement gun on my pressure washer?
A gun with a pressure rating above the machine's operating pressure can be suitable only if its flow, temperature and inlet/outlet connections also match. A higher maximum PSI rating does not fix an incompatible connection or temperature limit.
What is a short pressure washer gun used for?
A short gun reduces the distance between the trigger and an accessory and is popular for compact tasks such as vehicle washing or foam-cannon use. It still needs a correctly rated hose-side inlet and accessory-side outlet, and the connected nozzle or accessory must be suitable for the machine.
Why does a pressure washer gun have a trigger lock?
The lock is intended to reduce accidental trigger actuation when the gun is not being actively used. Follow the pressure-washer and gun manufacturer's safety instructions, depressurize before changing accessories, and never direct high-pressure spray at people or animals.