Guides to pressure washer hose fittings, couplers and adapters

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Hello, I am Santy, the funder of I have been in cleaning machinery field for more than 5 years now, and the purpose of this article is to share with you the knowledge related to pressure washer from a Chinese supplier's perspective.

This guide will teach you everything about pressure washer hose fittings, couplers, and adapters. Also, we’ll discuss all the different types, sizes, materials, and naming conventions used. What different accessories, couplers, and adapters can help you (4 examples included). And how to choose the right option for your setup.Let’s get started.

Guides to pressure washer hose fittings couplers and adapters 5

Why do you need pressure washer accessories?

Pressure washer fittings connect pressure washer components. It fits between the high-pressure hose and the trigger gun or between the pump and the pressure hose to be correctly connected.

Your pressure washer will come with the couplers, fittings, and adapters you need out of the box.

You will only start needing accessories when you:

  • Want to add attachments such as surface cleaner, foam cannon, pressure gauge, etc?
  • Want to use a different high-pressure hose (or extend the length of your existing hose)
  • Want to turn screw fittings for quick connections
  • We hope the hose kinks are better avoided by using a swivel fitting.
  • Fittings are inexpensive ($5-$15) and durable enough to make your life easier. There are hundreds of different accessories, but you only need to know a few types.

Types of fittings, couplers, and adapters

Fittings, couplers, and adapters can be considered the same thing. Sometimes websites will refer to the entire category of connectors as fittings and then refer to specific types of fittings as couplers, adapters, or reducers. But that isn’t very clear, and we won’t do that here.

However, we will discuss quick-connect fittings and swivel fittings separately.

Quick connect (QC) fittings

Quick connect fittings provide quick connect/release with a turn screw connection, making connecting and disconnecting hoses fast and easy.

Female quick-connect hose fittings (sometimes called sockets) have O-rings to prevent leaks. The male side is sometimes called the plug.

Most hoses today are equipped with QC connections out of the box.


The swivel prevents the hose from kinking while in use and helps loosen the hose the first time you step out.

It allows the hose to swivel without twisting the gun and extension wand a large turn. You just walk it out, and the gun swivel twists the hose kinks as you go. This is one of those fittings you can’t pressure wash without trying once.

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Materials used to make accessories

Consider what the accessory must do:

  • It has to be strong enough to withstand (likely) 1000 – 4000 psi over thousands of cycles.
  • It needs to hold the parts together firmly and not break even with constant tugging by the user.
  • It needs to be corrosion-resistant because it has water inside.
  • It has to be cheap enough to be a commercially profitable product.

Brass, stainless steel, and plastic are the most common materials for pressure washer hose fittings.

Brass is the most common. Then there’s plastic (plenty of home electric pressure washers). Then there’s stainless steel which is very common in professional use because of its chemical resistance.

Let’s have a look at the pros and cons of each:


Plastic fittings are for light-duty electric pressure washers only.

Pros – cheap and light

Cons – Easily cracked and damaged


Brass is by far the most common material for pressure washer fittings. It is an alloy of copper and zinc with a low melting point and is easy to cast and machine.

Pros – strong and corrosion resistant. Easy to process into different shapes. Cheaper than stainless steel.

Cons – More expensive than plastic.

Stainless steel

Stainless steel has chromium added to prevent rust.

Pros – Best corrosion resistance, chemically resistant, and high strength.

Cons – Expensive.

Rubber O-rings

O-rings are used in female fittings to prevent leaks. The quick-connect male fits into the female receptacle, and the o-ring is just the size to avoid leaks.

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Size of fittings

The primary confusion when shopping for accessories is the size you need.

  • Are you measuring inside or outside diameter?
  • How precise do you need to be?
  • Did you include threads in that measurement?

Even with digital calipers, this isn’t easy. Some fittings are 3/8”, while some are 22mm, and some are 14mm inside diameter, sometimes you will find fittings that do not conform to British pipe thread standards, some are marked QC F or QC M so that is confusing.

How to measure fittings and connections

To correctly measure the fittings you need, calipers are required. A tape measure would work too, but it won’t work as well since we’re talking about 1mm differences.

Here are some other things to know when talking about power washer adapters:

Male (M) to female (F) connection

The male side has a pin or plug that fits into the female hole or socket. The female fittings accept the male connector and hold it in place.

NPT and BPT/BSP pipe thread standards

NPT = National Pipe Thread. American standard for screw threads.

BSP = British Standard Pipe. British standard for screw threads.

Why should you care about BSP and NPT?

Because sometimes the pressure washer coupler is NPT, and sometimes it is BSP. They don’t mesh together.

Example: 3/8” pipe size, according to NPT, has a pitch of 0.05555” (1.411mm) and an OD of 0.675” (17.145mm). The same 3/8” pipe has a pitch of 0.0526” (1.337mm) and an OD of 0.6560” (16.662mm) per BSP.

They’re close but imprecise, and you can’t connect a 3/8” male NPT screw to a 3/8” female BSP connection more than 4 or 3 turns before it locks.

External and internal diameters

When measuring, you need to pay attention to the inside and outside diameter of the fitting. An M22 screw connection on a gas pressure washer has an internal diameter of 14 mm, but the same M22 screw connection on an electric washer has an inner diameter of 15 mm.

Guides to pressure washer hose fittings couplers and adapters

Different Sizes You’ll See: M22 thread, 3/8” thread, and quick connect

M22 threads are commonly found on hoses, pumps, and spray guns

The outer diameter (OD) is 22mm, the inner diameter (ID) is 14mm, and the inner plug on the female M22 side is 14mm. O-ring on the female side to prevent leaks.

Also, note that there is an M22 for use on electric pressure washers, but it has a 15mm inner diameter.

3/8″ BSP thread size

This is the British standard pipe thread (BSP) naming convention. This is the imperial designation for the fitting size, not the size. The actual primary diameter of a 3/8” BSP thread is approximately 16.66mm (~2/3”).

Quick connect plug and socket dimensions

All the quick connect we’ve seen are 3/8” QC. You don’t need to take out the caliper for quick connects.

Things to consider when purchasing pressure washer fittings

What matters is the size of the pressure washer. Let’s look at some details you might want to consider based on your preferences.

  • If you want to get the job done quickly, choose quick-connect fittings. Quick-connect fittings install in less than 15 seconds, so you can get work done faster.
  • Swivel fittings are a great option because they eliminate twists and kinks. This is an important point; you will be grateful when you finish the job. You’ll find a big difference with and without pressure washing.
  • For larger jobs, you may need a splitter. You can connect two pressure washers simultaneously to increase the pressure. This will make heavy tasks easier and faster for you.
  • Material matters when choosing pressure washer fittings. Due to its corrosion resistance and durability, we recommend brass or stainless steel.
  • Also, always double-check if the fitting is UK or US. This will help you analyze if it is installed correctly and avoid leaks.

How do I know what size pressure the washer hose is?

Pressure washer hoses are designed for extreme durability but wear out after a few years of use. Knowing your hose size is essential when looking for a replacement. You may also need dimensions for accessories like foamers or surface cleaners.

Manufacturers will specify the length of each pressure washer hose, ranging from 20 to over 50 feet long.

As far as diameter goes, you can use the same diameter as a regular garden hose or consult the manufacturer (or owner’s manual, if you have any!). The most common diameter is 1/4 inch. The least common diameters are 3/8” and 5/16” hose.

The best way to find the best size pressure hose is to take the original hose to a professional, or if you’re unsure, contact the manufacturer. Fortunately, accessories are usually pretty cheap.

Does hose diameter affect water pressure?

Yes! In the simplest explanation, the larger the diameter, the higher the water pressure produced.

Think of it like a faucet: when you turn it to the right, water comes out with great speed and high pressure. When you turn it a little bit, the power of the water decreases.

The same goes for hose diameter. Most regular hoses are 1/4” or 1/2” in diameter, which will provide more water pressure. Anything smaller will still provide high-pressure water, depending on the pressure washer engine or motor, but at a lesser pressure.

If you’re having trouble with your hose, whether for garden use or a pressure washer, it could be due to the diameter. Other problems include leaks, low water supply pressure, kinks or bends, or improperly connected hoses.

Hose length also affects water pressure. The longer the hose, the lower the flow rate.

Are pressure washer hoses universal?

Every part of a pressure washer is designed according to whether an electric motor or a gasoline engine runs it. This means the nozzle, gun, and hose are not universal for pressure washers.

Some hoses are better suited for higher pressures than others; the motor or engine can determine this. The higher the quality of the material, the more expensive the hose.

Pressure washer hoses vary in length and how they connect to the water source and gun. Before purchasing a hose, check whether it has male and female connectors. This is another reason why pressure washer hoses are not universal: they don’t all connect the same way.

Gas pressure washers are more likely to be generic electric pressure washers, and they are usually brand-specific and require parts supplied explicitly by the manufacturer. This can make a difference when you’re looking to purchase a pressure washer.

Can I turn a hose into a pressure washer?

Pressure washers can be expensive, bulky, and unnecessary. Luckily, it’s possible to turn a hose into a pressure washer!

It would help if you had a functional hose with a water jet with multiple functions. These range from spraying (great for watering flowers) to powerful. This will be a thinner water line but flow at a high velocity.

Our number one recommendation is to keep the hose as short as possible, as longer hoses require more distance for the water to flow, which means less pressure.

Before attempting this, ensure your hose is in good condition and run the water through the faucet to the highest setting. If there are kinks and potential leak areas, it won’t be able to hold up to water pressure.

While a regular hose isn’t as powerful or effective as a pressure washer, it’s an effective way to remove loose stains.


When choosing fittings, it all depends on the size of your pressure washer. You need to consider the type and material of your pressure washer fittings. Brass and stainless steel provide superior durability and corrosion resistance. Quick connector fittings offer maximum convenience and can be installed in minutes. Swivel fittings also help avoid twisting or kinks.

On the other hand, splitters are great for heavy work that requires more pressure. It is essential to know whether the accessory is American or British. Choosing fittings that won’t leak and last a long time is vital. Still, it has to be able to deliver outstanding performance without issue.

FAQs about pressure washer hose fittings, couplers and adapters

These pressure washer hoses can be used in a variety of ways. There are various options for hoses. They can vary in length and diameter. You can’t just purchase any hose to replace what you have. Either you end up with a hose that isn’t as good as you expected, or you can’t connect the device to the hose at all.

It is possible to use a pressure washer without an external faucet if the water source is high enough to supply enough water to the pressure washer pump. This can be done if you have a pressure washer with a water supply or can draw water from an outside source.

There are three types of connections on gas units: M22, 3/8” thread, and quick connect. Only lance and guns are exempt.

Gas pressure washers are available with a broader range of accessories, which makes them easier to match with different fittings and couplings. Electric pressure washers are brand-specific, so only certain accessories or parts will work.


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