Plumbers, pipes and German vs English standards

A lot of plumbers get problems installing a water softener because they do not understand the relationship between Deutsch Industrial Norme (DIN) & British Standard Pipe (BSP).

Over the last few years a number of continental plumbing systems have been introduced to the UK and this can cause great confusion when installing a water softener and having to break into the existing plumbing in the household and connect up a bypass set to fit your Harvey Water Softener.

What most people do not appreciate is that Whitworth invented the standardised thread-form back in 1841 and the British Empire spread this around the world.

When they decided on a standard thread for plumbing pipework, the British Standard Pipe Thread, it was the Whitworth thread-form that was adopted.

This also spread around the world and virtually every continent uses this system.

However, there are two anomalies.

The German’s didn’t like the idea of recognising the English BSP so they called their system DIN.

It is in fact exactly the same thread-form as Whitworth so to identify the correct thread size under the DIN Standard, you have DIN 15 equalling BSP half inch. DIN 20 equalling BSP three quarter inch and DIN 25 equalling BSP one inch.

Our dear friends the Americans went one better and they called their system NPT, National Pipe Thread.

Just as they changed the size of the Imperial gallon to the US gallon, they changed the thread-form from Whitworth to something entirely different. So instead of having the Standard 55 degree angle on the threads, they changed it to 60. (Yes you have to ask yourself why?).

The net result is that whereas the DIN pipe threads are interchangeable with BSP pipe threads, the American NPT pipe threads are not. You can graunch a half inch NPT into a half inch BSP fitting and the sealant will take up the slack.

However, three quarter inch and above in size that does not work, so you have to make up the correct type of adaptors.

All of this knowledge is part of the Harvey Water Softeners experience. We are the experts in installing a water softener and if you want to have a water softener installed by the people that know what they are doing, then get it installed by Harvey Water Softeners.

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