Hi Nick
I know that connector sizes are not quite the same but, when looking
through my father in law's collection of tap washers, there were a
lot of 1/2" and 3/4", some 5/8" and two 9/16" ones.

I have once in 30 years come across a 7/8" BSP tap. Lewisham Council used
them on the ground floor of tower blocks. The taps are for washing the bin
areas, but they got huge water bill because the residents used them for car
washing.

They changed all the tap threads to 7/8" so the residents can't connect to
them.

On a similar basis, I did hear that Ford Motor Co in Dagenham have all their
3 pin 230v sockets & plugs made with the earth pin horizontal and the
live/neutral vertical. It was to stop the theft of plugs which cost Ford a
fortune every year.

Dave