M22
A common hand-tightened threaded interface on residential hoses, guns and wands. The outside thread name does not settle the internal sealing-stem size; 14 mm and 15 mm variants both exist.
Home Pressure Washer Fittings & Quick Connects
Connection identification
Pressure Washer Fittings & Quick Connects: M22, 3/8 & 1/4
Pressure-washer fittings are not universal. Identify the connection family, exact size/subtype, male or female half, pressure rating and temperature rating before adapting a hose, gun, wand or accessory.
Identify before adapting
Connection family → nominal size → male/female half → M22 stem subtype if applicable → pressure rating → temperature rating.
Do not choose an adapter from a photo alone. Technical examples reviewed: August 28, 2026.
The three connector families you will see most often
3/8-inch QC
Common on high-pressure hose connections in professional-style systems. SIMPSON's Monster hoses use 3/8-inch QC ends, and professional gun kits often use a 3/8-inch inlet.
1/4-inch QC
Common on the wand/nozzle/accessory side. Current SIMPSON wands use 1/4-inch QC sockets at the nozzle end; many professional guns are configured with 1/4-inch outlets. The nozzle guide covers the separate orifice-sizing requirement.
Proprietary / OEM interfaces
Some consumer systems use proprietary couplers, 15 mm M22 variants or integrated hose-reel connections. The exact washer model can matter even when an aftermarket kit lists the brand.
M22 14 mm vs. 15 mm: the thread can look the same
M22 is often treated as if it were one universal pressure-washer connection. That is the mistake this page is designed to prevent. MTM Hydro documents a standard 14 mm stem in its M22 Hydrojet family and a separate 15 mm adapter for certain consumer pressure washers. Its guidance recommends measuring the connection in millimeters, with a digital caliper preferred for accuracy.
M22 14 mm
Common aftermarket M22 stem size. MTM identifies its standard Hydrojet M22 fittings as 14 mm unless a product is specifically marked 15 mm.
Do not identify it from the M22 thread alone.
M22 15 mm
Used on some consumer systems. MTM documents 15 mm adapter paths for select Sun Joe, Ryobi, AR and Greenworks applications, but exact-model checking is still required.
Do not assume every model from a listed brand uses 15 mm.
Practical rule: if an M22 connection is part of the replacement path, record the stem/receiver dimension as well as the thread family. A listing that says only “M22” may not provide enough information.
3/8-inch vs. 1/4-inch pressure washer quick connects
These sizes often occupy different places in the same pressure-washer system. A common professional pattern is 3/8-inch QC on the hose side and 1/4-inch QC on the wand/nozzle side. For example, MTM's SG28 gun is specified with a 3/8-inch inlet and 1/4-inch outlet, while SIMPSON's Monster hose uses 3/8-inch quick connects and its 31-inch wand ends in a 1/4-inch QC nozzle socket.
| Typical location | Common documented interface | Example | What still needs verification |
|---|---|---|---|
| Pressure washer ↔ hose | M22 or 3/8" QC | MorFlex M22; Monster 3/8" QC | Subtype/gender, PSI, temperature and model outlet. |
| Hose ↔ spray gun | M22 or 3/8" QC / threaded port | SIMPSON 80178 has 3/8" FNPT inlet; adapters supplied | Gun configuration and installed adapter. |
| Spray gun ↔ wand | M22 or 1/4" threaded/QC depending system | SIMPSON 80479 uses M22 gun connection | Gun outlet and wand inlet. |
| Wand ↔ nozzle/accessory | 1/4" QC is common | SIMPSON 80479 uses 1/4" QC socket | Accessory plug size and pressure/flow requirements. |
“Typical” describes a common layout, not a universal rule. Match the product documentation in front of you.
Male/female wording: record the connection, not just the number
A quick-connect system has a plug and a socket/coupler. Threaded ports can separately be male or female. That means “3/8 fitting” is incomplete information: a 3/8-inch QC plug is not the same part as a 3/8-inch QC socket, and neither description says what thread or port exists behind the quick-connect body.
When documenting a connection, write the entire path—for example, 3/8-inch QC male plug → hose or M22 14 mm coupler → 3/8-inch QC socket. This makes adapter selection much less ambiguous.
A simple pressure-washer connection worksheet
| Side A | Record | Side B | Record |
|---|---|---|---|
| Machine outlet | Connection family, size/subtype and gender | Hose machine end | Connection family, size/subtype and gender |
| Hose gun end | Connection family, size/subtype and gender | Gun inlet | Connection family, port/QC type and gender |
| Gun outlet | Connection family, port/QC type and gender | Wand inlet | Connection family, size and gender |
| Wand outlet | Usually identify QC socket or thread | Nozzle/accessory | Matching plug/thread plus flow/pressure requirement |
Then compare the pressure and temperature rating of every part in the proposed path. An adapter can make two shapes connect; it does not raise the ratings of the hose, gun, wand or accessory.
Adapter kits and brand-specific systems
Brand-specific connection guides: RYOBI · SIMPSON · Kärcher · CRAFTSMAN · DEWALT · Greenworks · Sun Joe · Generac · Troy-Bilt.
Aftermarket kits can be useful when a consumer pressure washer uses an interface that does not match standard professional hose/gun components. MTM's current kits include both 14 mm and 15 mm M22-to-3/8-inch-QC adapter options and list many common brands, while explicitly warning that select models can require other fittings.
This is the right way to interpret a brand list: it is a starting point for identifying the adapter family, not proof that every machine carrying that brand name uses the same connector.
The same caution applies to attachments. A foam cannon with a standard 1/4-inch plug can still need a low-profile or model-specific adapter on some residential couplers, while a surface cleaner may connect at the 1/4-inch wand side or the 3/8-inch hose side depending on its design.
Keep the adapter chain as simple as the documented interfaces allow
Every fitting in a high-pressure path has to be mechanically secure and suitably rated. If one correctly rated adapter can bridge a documented interface, there is usually no reason to build a longer stack merely because extra couplers are available. Re-check the complete path after any conversion.
After you identify the exact connection type
Use the connector family, size, gender and M22 stem subtype you recorded above to compare current fittings. Do not buy a generic “universal” adapter assortment as a substitute for identifying the actual interfaces.
Technical sources
- MTM Hydro — Adapting consumer electric pressure washers — recommends measuring 14 mm vs. 15 mm M22 connections and documents adapter-kit groupings.
- MTM Hydro — M22 15 mm to 3/8-inch QC adapter — documents a distinct 15 mm stem receiver and 4000 PSI rating.
- MTM Hydro — M22 fitting terminology — identifies standard Hydrojet M22 stems as 14 mm unless marked 15 mm.
- SIMPSON — 2026 Industrial Catalog — current gun/wand connection tables illustrating common 3/8-inch and 1/4-inch roles.
- SIMPSON — Monster Hose 41030 — current 3/8-inch plug/socket hose example.
- SIMPSON — Wand 80479 — current M22 gun-side / 1/4-inch-QC nozzle-side example.
Frequently asked questions
Are pressure washer fittings universal?
No. Pressure washers commonly use M22 threaded fittings and 3/8-inch or 1/4-inch quick connects, but size, gender, M22 14 mm vs. 15 mm stem subtype, pressure/temperature rating and proprietary interfaces can differ.
What is the difference between M22 14 mm and M22 15 mm?
Both use the M22 threaded connection family, but the inner sealing stem/receiver dimension differs. MTM Hydro recommends measuring the connection in millimeters—preferably with a digital caliper—before choosing a 14 mm or 15 mm adapter.
Is 3/8-inch quick connect the same as 1/4-inch quick connect?
No. They are different quick-connect sizes. In common professional pressure-washer layouts, 3/8-inch QC is often used on the high-pressure hose side while 1/4-inch QC is commonly used at the wand/nozzle or accessory side, but the exact product specification controls.
Can I stack multiple pressure washer adapters together?
Adapters can solve legitimate interface differences, but every added connection must be correctly sized and rated for the pressure and temperature. Prefer the simplest properly rated connection path that matches the documented interfaces instead of building unnecessary adapter stacks.
How do I know whether I need a male plug or female coupler?
Identify the actual mating half on the pressure washer, hose, gun or wand. Quick-connect gender refers to the plug and socket/coupler, while threaded fittings have their own male/female thread description. Record both the connection family and gender before buying an adapter.