Connect 3/8" BSP parallel (G3/8 / BSPP) to 1/2" BSP parallel (G1/2 / BSPP)
How to join G3/8 and G1/2, and what stops it leaking.
Needs adapter
End A
3/8" BSP parallel (G3/8 / BSPP) (G3/8)
Seals on flat washer or bonded seal on the face
via adapter
End B
1/2" BSP parallel (G1/2 / BSPP) (G1/2)
Seals on flat washer
Adapter neededG3/8 to G1/2 tap tail adapter
Not a direct fit. Joining 3/8" BSP parallel (G3/8 / BSPP) to 1/2" BSP parallel (G1/2 / BSPP) needs a G3/8 to G1/2 tap tail adapter.
The adapter to buy
Search Amazon for G3/8 to G1/2 tap tail adapteraffiliate searchFind G3/8 to G1/2 tap tail adapter on eBayaffiliate
A G3/8 flexible tap tail steps up to a G1/2 valve or fitting with a short parallel adapter. Both seal on a washer at the face, so the join is reliable once the washer seats.
Check the tail is G3/8 and not the finer M10 monobloc thread some mixer tails use. They look similar but the M10 will not start into a G3/8 adapter.
Related connections
3/8" BSP parallel (G3/8 / BSPP)G3/81/2" BSP parallel (G1/2 / BSPP)G1/2Garden Hose Thread (GHT / NH) to 1/2" BSP parallel (G1/2 / BSPP)adapter1/2" BSP parallel (G1/2 / BSPP) to 3/4" BSP parallel (G3/4 / BSPP)adapter1/2" NPT (National Pipe Taper) to 1/2" BSP parallel (G1/2 / BSPP)adapter
Sources: ISO 228-1 (G / BSPP parallel pipe threads) · BSP thread dimensions chart (ISO 228 / ISO 7), AmesWeb