5/8" BSP?

Question

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.

Nightjar · Accepted Answer

to a galvanised steel pipe, thinking it was 1/2" BSP, bought the compression coupler and found that it's larger - a little more than 5/8" internal diameter. What's going on?

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 mystery brass thread on a hexagon nipple. The other side of the nipple (which incidentally *is* 1/2") connects to the galvanised steel pipe.

A picture speaks a thousand words.

Colin Bignell

alamaison · Answer

ction to a galvanised steel pipe, thinking it was 1/2" BSP, bought the comp= ression coupler and found that it's larger - a little more than 5/8" intern= al diameter. What's going on?

ding 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= mystery brass thread on a hexagon nipple. The other side of the nipple (w= hich incidentally *is* 1/2") connects to the galvanised steel pipe.

ith it anywhere.

Finally got some:

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pics are a bit grotty but they show the end of the lead/copper pipe wit= h the nut and the brass BSP thread connected to the steel pipe coming out o= f the floor.

Nightjar · Answer

to a galvanised steel pipe, thinking it was 1/2" BSP, bought the compression coupler and found that it's larger - a little more than 5/8" internal diameter. What's going on?

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 mystery brass thread on a hexagon nipple. The other side of the nipple (which incidentally *is* 1/2") connects to the galvanised steel pipe.

it anywhere.

the nut and the brass BSP thread connected to the steel pipe coming out of the floor.

That is what I thought you were describing, but it is better to be sure. Unfortunately, there is no industry standard for that thread. As nut and fitting are used together, the manufacturers only need to match their own products, not be interchangeable with other makes.

It looks to be too old to be metric, so, if it is not 1/2" BSP, which is commonly used for 15mm compression fittings, the next most likely is British Standard Brass thread:

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it is, the thread, at 26 tpi, will be much finer than the 14 tpi of

1/2" BSP, but it is difficult to tell that from the photos. You may also find, if it is old enough, that the '15mm' copper pipe is actually imperial 1/2" pipe.

Colin Bignell

5/8" BSP?

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