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My plumber told me it was 1inch1. What makes you think they are 1"?
2. 3/4" BSP threads (the norm for bath taps) are 1.04 inches across the outside diameter.
3. One inch BSP threads are 1.3" across the outside diameter.
Reply to the thread, titled "Tap make for Traditional bath mixer tap with a non standard Fitting" which is posted in UK Plumbers Forums on Plumbers Forums.
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