Not for the first time in this house I've come up against a brass connectio= n to a galvanised steel pipe, thinking it was 1/2" BSP, bought the compress= ion coupler and found that it's larger - a little more than 5/8" internal d= iameter. What's going on?
Every time I've seen it it's while replacing a section of lead pipe leading= to a tap or cistern. The non-tap end of the lead is joined to a short bit= of copper pipe (15mmish) which ends in a BSP nut that screws onto this mys= tery brass thread on a hexagon nipple. The other side of the nipple (which= incidentally *is* 1/2") connects to the galvanised steel pipe.
Is this some custom connection? I can't find anything that will mate with = it anywhere.