Connect Garden Hose Thread (GHT / NH) to 3/4" BSP parallel (G3/4 / BSPP)
How to join 3/4"-11.5NH and G3/4, and what stops it leaking.
Not a direct fit. Joining Garden Hose Thread (GHT / NH) to 3/4" BSP parallel (G3/4 / BSPP) needs a GHT female to 3/4 BSP male adapter.
The adapter to buy
A US or imported garden hose (GHT) will not thread safely onto a UK outdoor tap (3/4 BSP): the pitch is different, 11.5 versus 14 threads per inch. Use a GHT-to-BSP brass adapter. It seals on the tap washer, so check the washer is present and undamaged.
Do not force a GHT coupling onto a BSP tap. It feels like it starts, then cross-threads and never seals. The adapter is a two-pound brass part that solves it permanently.
Related connections
Sources: ASME B1.20.7 (garden hose / GHT / NH threads) · NPSH / NH / NHR hose coupling thread table, Fittings.space · ISO 228-1 (G / BSPP parallel pipe threads) · BSP thread dimensions chart (ISO 228 / ISO 7), AmesWeb · Washing-machine / dishwasher inlet 3/4 BSP connector data