Washer sizes


9 Jan 2007
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United Kingdom
I went to look for some replacement washers today (yes, I know, Sunday). What I needed was 15-16mm tap washers, but all I could find at a pound shop was stated to be 1/2". When I got them out they turned out to be 3/4"! Far too big, so I had to cut them down slightly or they wouldn't go through the holes in the taps.
It is usual for washer sizes to be stated arbitrarily? I also see that a review on Screwfix stating that the supplied washers were nowhere near the stated size.

Incidentally, one of the cheapo washers split when I tried to push it on to the inside mounting of the tap so I'm not sure exactly how long they'll last, although all four taps seem to work well at the moment.
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Sounds like you needed ⅜" washers. Sizes aren't arbitrary - all ½" tap washers are the same size, as are the others - but they don't bear any relation to what you'd find on a tape measure. They're the same size as threaded fittings
Thank you both. That's very helpful, especially the 'conversion chart' which I'll copy and print out for future use! I think I might be forgiven, as a non-expert, for not knowing about this system.

All I could do was to measure one of the old washers and work from that. Although they were all squashed flat and, therefore, oversized due to people over-tightening the taps (not us - they've been there longer than we have) I could see the flat and level area of the 'business end' of the inside of the tap and that measured about 16mm which is, as one of you said, 3/8" by the measurements plumbers use!

Incidentally, these are Bristan, Birmingham taps which I would have thought would take standard washbasin-sized washers.

Now I know, I'll get some '3/8inch' washers and do the job properly. Thanks again.
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