Pressure Washer Fittings 101: Fittings and QD Naming
A Deep Dive into the Obsessed Garage Approach to Naming Fittings and Quick Disconnects.
Any time you search the web for pressure washer fittings you get bombarded with industry jargon, inconsistent terminology, and confusing naming schemes. Even on Obsessed Garage the vast amount of options can get a little overwhelming. If you're having trouble sorting through the mess, this article should be exactly what you need.
Where to Start?
In the pressure washer world, we are always trying to connect some piece of equipment or accessory to some other thing or piece of machinery. Sometimes these connections can be a direct fit, but most of the time there is a difference in connection type that requires some sort of adapter or fitting. At Obsessed Garage, most of our fittings are of the Quick Disconnect (QD) type. We figure, if you're going to have to use an adapter or fitting anyway, you might as well make it a QD so that you can easily connect and disconnect.
For pressure washer fittings that we use, there are four nomenclatures that we use:
QD Connection Type
When we title our fittings and QDs on the site, we always list the thread size, and almost always the thread type. For some fittings, we will just use size in the title and put the thread type in the description for parts that are commonly only using one type of thread. In those cases, it's usually only needed to know the size. Common thread sizes that you'll see in our store are 1/4", 3/8", 1/2", 3/4", and M22. However, there can be different types for these sizes which we'll discuss next.
NPT: In the US, for standard pipe connections, National Pipe Thread (NPT) is the most common type. These types of threading come in 1/4", 3/8", 1/2", and 3/4" sizes in our store. The thing with NPT though is that the size can't really be measured on the actual threads and is more related to the internal diameter than it is to the thread size. If you were to measure the outer diameter of 3/8" NPT you would quickly find that it's a bit larger than 3/8".
NPT is also a tapered thread that requires pipe tape or sealant to create a tight seal. There is not an o-ring connection in an NPT application, so the connection of the male and female threads and pipe tape is the only thing creating a nice seal. This is why some of our products come with fittings installed extremely tight.
GHT: Garden Hose Thread (GHT) is commonly used on water faucets, hose bibbs, and garden hoses. GHT is always in a 3/4" size and is not tapered like NPT. Also unlike NPT, the thread in this type of connection has almost nothing to do with the seal and keeping leaks away, other than being the tightening agent. In a GHT connection, there is always a rubber washer acting as a seal in the female threaded end of the connection. The threads allow the two points to be drawn close together and press against the rubber washer. This creates a watertight seal. The use of pipe tape or sealant in a GHT connection will actually invite leaks rather than solve them. Always check the rubber washer if you're having garden hose leaking issues.
14mm and 15mm M22: M22 both a thread size and a connection type in the pressure washer world. This type of connection is commonly found on a standard pressure washer hose and it's connection to the machine and to the sprayer. Many OE sprayers and wands have an M22 connection between. The nice thing about an M22 connection in a high-pressure scenario is that there is an internal o-ring on the internal shaft of the connection. This creates a nice tight watertight seal. Much like GHT, the thread doesn't provide the seal, and pipe tape should not be used. This connection type and the 14mm and 15mm variants define the size of that inner shaft. Kranzle, Karcher, Greenworks, Ryobi, and pretty much all gas pressure washers use the industry standard of 14mm M22. But 15mm has become very popular for the stuff coming out of China and Europe: SunJoe, AR Blue (residential line), Stanley, and others.
BSP, BSPP, BSPT: British Standard Pipe is something we deal with every so often. P at the end standard for parallel, and T at the end standard for tapered. The main connection that uses BSPP is the inlet thread on a pressure washer prior to using a garden hose adapter. Many times people don't realize that an adapter is almost always needed on a pressure washer inlet and these are usually included with the machine. It will convert the male BSPP threads over to female 3/4" GHT for use with standard garden hoses.
At Obsessed Garage, anytime you see male or female in the title of a product, it is always related to the thread gender. We never name a connection type not relating to thread by gender and only use that connection type's name. For example: Male 3/8" Plug has male 3/8" NPT threads.
QD Connection Type
Contrary to thread gender, we never call a QD connection male or female. We use the terms plug and coupler. A plug is technically a male end, but we just call it by plug. And a coupler is technically the female end of the connection that receives a plug, but we just call it a coupler. Because of this, you can easily determine what a product is on our site based on the terms we use. Example: Female 3/8" Plug is a female threaded 3/8" NPT connection with the male QD end (plug). Rather than calling it a Female 3/8" Male Plug, we just reserve the gender specifically for the thread type.