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Now this is where things get a little complicated.

The first thing you need to understand is the difference between a male thread and female one.

A male thread screws into a female one.


Different Types of Thread

There are three different types of thread:

BSP - British Standard Pipe

Metric - M

NPT - National Pipe Thread (this is the thread used in America)

Most British machines use BSP as this is the standard thread in the UK and around the majority of the world.

Problems occur when you bring in equipment from America which is NPT and then have to find fittings for it when everything over here in the UK is BSP.


Different Sizes in the Threads

Each thread has a number of different sizes. To work out the size of your threads you take a ruler and measure the diameter across the outside of the male threaded end or across the inside of the female threaded end.

Make sure you measure from where the actual thread begins and stops. It is a common mistake when measuring a female fitting to measure across the entire fitting.

If you're lucky it will have somewhere on your fittings the size of them. On some of my fittings it says 38 which means 3/8.


Fitting Size       Female      .........Male
1/8" BSP          ...... 8.566mm  .............9.728mm
1/4" BSP         ...... 11.445mm   ..........13.157mm
3/8" BSP          ......14.950mm   ..........16.662mm
1/2" BSP         .......18.631mm    ...........20.955mm
3/4" BSP          ......24.117mm    ..........26.441mm
1" BSP             ........30.291mm    ..........33.249mm
1 1/4" BSP       ......38.952mm    .........41.910mm
1 1/2" BSP       ......44.324mm   .........47.803mm
2" BSP             ........56.656mm   .......... 59.614mm



Fitting Size....... Female ......Male
M12                 ...........10.105mm      12mm
M14                 ...........11.835mm      14mm
M16                 ...........13.835mm      16mm
M18                 ...........15.294mm      18mm
M21                 ...........18.294mm      21mm
M22                ........... 19.294mm      22mm
M24                ........... 20.752mm      24mm
M27                 ...........23.752mm      27mm
M30                ........... 26.211mm      30mm


High Pressure Hose

The hose you use between your pressure washer and lance is special hose made from wire because of the high pressure the water is being pumped along it.

The connectors on the end will usually be BSP and they'll also probably be female. So this means you'll want to have a male BSP connector on the end of your lance and on the outlet of your pressure washer.

The ends of the hose, where it joins to the pressure washer and the lance will wear out and split over time. You'll need to find a hydraulics company near you that will be able to fix this problem for you when it occurs. This also means that you'll should have a backup wire hose in your van with you at all times ready to go.


Quick Release Connectors

You can have fitted onto your pressure washer, high pressure hoses, lance and flat surface cleaner quick release connectors.

Quick Release Connectors allow you to rapidly change between your flat surface cleaner and lance.

On your hose you will most likely have female BSP connectors.

There are three different sizes of quick release connector:

Mini - 11.6mm

Midi - 14.6mm

Standard - 20mm



Image from powerwashinguk.co.uk

In this image you can see how you measure a male quick release connector.

This is the standard male QRC as the probe measures 20mm.

This photo only displays half of the male QRC. At the other end of this QRC will be most likely be a female BSP fitting.

The diameter across a female QRC is slightly larger than the male connectors. The opposite is true with the standard BSP, Metric and Npt fittings because they are screw-in fittings, while a QRC slides in, hence the name quick release because they are faster.


On some of my quick release connectors it has written on them 3820. 38 stands for the 3/8 which is the BSP size and 20 for the 20mm standard sized quick release connector.


Running Water to your Buffer Tank

You run water to your buffer tank or directly to your pressure washer with garden hose and the same outside tap connectors you get at B&Q.

When you buy your pressure washer you should get supplied a thing called a hose barb that you screw into your pressure washer's water inlet, and push your garden hose onto the other end. This is positive flow.

You may need to connect your garden hose that's going to feed your pressure washer or buffer tank to an inside tap as some customers won't have an outside tap. To do this you'll need an inside tap connector. It's probably best to purchase the hose multi-tap connector as these should be able to connect to all the different types of inside tap. You can also buy them from B&Q.





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