Garden tap thread size

May 23, 2013 Last reply: 2 years ago 27 Replies
K

I've been trying for days to find a hose connector for our outside tap with no success after our old one broke last winter. i've bought 3 different connectors, 2 were just a few milimeters too big and 1 was too small. have tap sizes changed in recent years or something? the tap in our back yard has been there since before we moved in 27 years ago. its reached the point where i plan to get a plumber out to see about fitting a new standardised tap. because we need to get the driveway pressure washed

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J

Have you measured the diameter of the threads on the tap?

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B

Most seem to be the same size- not just in the UK but even in Europe. I use the same adaptors when on campsites in France etc. as at home.

That said, I’ve notice some cheap adaptors are under size- either poor tolerances or perhaps they are some other thread which nearly fits- you can use them with brute force. Look for ones with a definite cylindrical shape, the problem ones tend to have bowed walls and a thin top edge.

Oddly, the BSP (British Standard Plumbing) sizes are still used even now in Europe.

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C

That is because the International Standards Organisation adopted the British Standard Pipe thread as the ISO standard for pressure tight (ISO

7-1:1994) and non-pressure tight (ISO 228-1:2000) pipe threads.
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T

Otherwise known as G plus the size in mm, eg G25 is 1" BSP.

Theo

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C

I thought that DIN specification, from the German Gewinde, but I don't know the ISO standard in detail, except as it is used in the UK.

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R

They're all likely to be one of several BSP sizes. Note: The BSP size refers to the nominal bore, so the outside diameter is somewhat bigger. See the table at

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The default outlet size for outside taps is 3/4" BSP. But some are 1/2" BSP or even 5/8" BSP.

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