Pressure washers are powerful cleaning tools that rely on high-pressure water to blast away dirt, grime, and debris. While the machine itself gets most of the attention, one of the most important aspects of a pressure washer’s performance is often overlooked: the fittings and connectors that link the hose, gun, pump, and accessories.
These small components play a major role in ensuring water flows efficiently and safely through the system.
Among the many types of connectors found on modern pressure washers, M22 fittings are the most widely used. If you’ve ever purchased a new hose, spray gun, or adapter, you’ve likely encountered the term, even if you weren’t sure what it meant.
This article will explain what M22 pressure washer fittings are, how they work, the different thread types, and why they have become the standard for many pressure washers.
What Are M22 Pressure Washer Fittings?
M22 fittings are threaded connectors commonly used to attach pressure washer hoses, guns, pumps, and adapters. They get their name from the 22mm outside diameter of the male connector.
“M22” as a Metric Measurement
The “M” stands for metric, and the “22” refers to the 22-millimeter outer diameter of the threaded portion. This sizing format is common in European-style threading and has become a standard within the pressure washing industry.
Common Applications
M22 fittings appear in:
1. Consumer-grade electric pressure washers
2. Prosumer gas pressure washers
3. Standard OEM hoses and guns
4. Many aftermarket accessories
They are particularly common on brands like Sun Joe, Ryobi, Simpson, Karcher (varies by model), Greenworks, and more.
Typical Materials
M22 fittings are made from:
1. Brass – durable, corrosion-resistant
2. Stainless steel – strongest and longest-lasting
3. Plated steel – affordable but less corrosion-resistant
4. Plastic – lightweight, typically seen in low-pressure electric models
Understanding M22 Thread Types
A. Metric Thread Overview
Metric threads follow a standardized measurement system used worldwide. In pressure washers, metric threads help ensure consistency and compatibility between different manufacturers.
Why It’s Used in Pressure Washer Designs
Manufacturers prefer metric threads because they:
➡️ Provide more precise tolerances
➡️ Improve sealing under high pressure
➡️ Are compatible with global suppliers and parts
B. M22 14mm vs. M22 15mm
Key Differences
Though both have the same 22mm outside diameter, the inner diameter of the male insert differs:
➡️ 14mm inner diameter
➡️ 15mm inner diameter
This small difference significantly impacts compatibility.
Why It’s the Most Common Compatibility Issue
A 14mm hose may not seal properly with a 15mm gun (and vice versa), causing leaks or pressure loss. Many users assume “M22 is M22,” which leads to confusion.
How to Identify Your Size
You can determine your fitting size by:
➡️ Checking your pressure washer’s manual
➡️ Looking up your brand specifications
➡️ Measuring the inner post on the male fitting
Consequences of Mismatching
Using the wrong size may cause:
➡️ Leaking at the connection
➡️ Damaged threads
➡️ Reduced pressure output
➡️ Unsafe operation
Components That Use M22 Fittings
A. Pressure Washer Hoses
Most hoses use M22 connectors on each end.
Inlet vs. Outlet
1. Inlet hoses connect the pump to the spray gun
2. Outlet hoses connect the pump to the water source
Brand Compatibility
Common examples:
1. 14mm: Sun Joe, Greenworks, Ryobi (electric units)
2. 15mm: Simpson, DeWalt, Generac (gas units)
B. Spray Guns and Wands
Spray guns often have an M22 female fitting where the hose attaches.
OEM and aftermarket guns may differ, so many users switch to standardized aftermarket versions for better compatibility.
C. Pressure Washer Pumps
Pumps typically use M22 fittings for the outlet connection. Their design provides a strong, reliable seal thanks to deep threads and a recessed O-ring.
D. Adapters and Converters
Adapters make M22 fittings extremely versatile:
➡️ M22 to Quick-Connect: Convert your threaded fitting to a faster, tool-free style
➡️ M22 to 3/8”: Allow use of professional-grade hoses
➡️ M22 to M22 Extensions: Extend hose length or join two hoses together
Why M22 Fittings Are so Common
1. Industry-standard sizing across multiple brands
2. Excellent high-pressure sealing when paired with an O-ring
3. Easy maintenance and replacement
4. Flexible compatibility with dozens of accessories and adapters
Their widespread use makes it easier for consumers to find replacement parts without technical knowledge.
How M22 Fittings Seal
A. Threaded Design
The male and female threads engage securely, helping stabilize the connection and guide it into place.
B. Rubber O-Ring Seal
Most M22 fittings rely on an O-ring inside the female connector, which provides the actual watertight seal.
Why O-Rings Are Used
1. They create a flexible, pressure-resistant seal
2. They require less tightening force
3. They prevent metal-on-metal wear
Lubrication and Replacement
O-rings wear out over time. Regular lubrication and replacement help:
1. Prevent leaks
2. Maintain pressure
3. Reduce wear on threads
Compatibility Considerations
A. Brand Differences
Different manufacturers use different internal diameters:
➡️ 14mm typical brands: Sun Joe, Greenworks, Ryobi
➡️ 15mm typical brands: Simpson, DeWalt, NorthStar, Generac
Always verify the size before buying accessories.
B. Pressure Rating
PSI and GPM requirements matter. Higher PSI systems may require:
➡️ Brass or stainless steel fittings
➡️ Heavy-duty O-rings
➡️ Correct inner diameter
Most M22 fittings are rated for up to 4000 PSI, but always check manufacturer specs.
C. Choosing the Right Adapter
Use adapters when:
➡️ You want quick-connect plug-and-play convenience
➡️ You need to connect hoses of different sizes
➡️ You’re switching between different accessory brands
➡️ Adapters reduce stress on original connectors, extending equipment life.
Common Problems With M22 Fittings (and How to Fix Them)
A. Leaks
Common causes:
1. Worn O-ring
2. Mismatched sizes
3. Loose connection
4. Cross-threaded fitting
Fixes:
1. Replace O-ring
2. Re-tighten by hand
3. Verify correct size
4. Inspect threads for damage
B. Cross-Threading
Cross-threading occurs when the male and female threads are not aligned.
How to avoid it:
1. Start threading gently by hand
2. Do not force the connection
3. Ensure threads are clean
Signs of damage:
1. Metal shavings
2. Difficulty tightening
3. Visible deformity
C. Fittings Not Tightening Properly
Possible causes:
1. Wrong size (14mm vs. 15mm)
2. Debris in threads
3. Damaged O-ring
4. Incorrect thread pitch
Diagnosis:
1. Clean threads
2. Replace O-ring
3. Verify size and material type
How to Choose the Right M22 Fittings
Checklist
➡️ Correct size: 14mm or 15mm
➡️ Quality material for your use case
➡️ PSI rating that matches your machine
➡️ Intended application:
-
Home use
-
Commercial cleaning
-
Foam cannon
-
Hose extensions
Recommended Combinations
➡️ Home users: brass M22 quick-connect set
➡️ Prosumer/gas washers: stainless steel M22 fittings
➡️ Foam cannon users: M22 to quick-connect adapter for fast attachment
Tips for Maintaining M22 Pressure Washer Fittings
1. Inspect O-rings regularly and replace when worn
2. Store hoses and fittings in a cool, dry place
3. Use Teflon tape only when appropriate (not typically required on O-ring sealed M22 connections)
4. Keep threads clean
5. Avoid overtightening, which damages threads
Frequently Asked Questions
Are all M22 fittings the same?
No. The 14mm vs. 15mm difference is the most important detail to confirm.
Can M22 be used on hot-water pressure washers?
Yes, if the material is rated for high temperatures (brass and stainless steel are best).
Do M22 fittings require tools?
Usually not. Hand tightening is sufficient because the O-ring creates the seal.
Should I switch to quick-connects?
Quick-connects make attachments faster and reduce wear on threaded fittings. Many users prefer them for convenience.
Conclusion
M22 pressure washer fittings are among the most common and reliable connectors used in residential and prosumer pressure washers. Understanding the differences especially the 14mm vs. 15mm sizing, helps ensure your system runs efficiently without leaks or pressure loss.
By choosing the right materials, maintaining O-rings, and verifying compatibility, you can extend the life of your pressure washer and enjoy smoother, safer operation.
If you’d like help choosing the right M22 fittings or want recommendations based on your pressure washer model, feel free to ask!
Post time: Nov-25-2025