Joining lead pipe to copper pipe

27 Oct 2004
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United Kingdom
My parents need some plumbing work doing to their house. The bath and sink in the bathroom still use original lead pipe up to the taps. I need to splice copper pipe into this original lead pipe to change the taps and also move them during installation of a new bath and sink. I have noticed that previous work by another plumber, years ago, when installing a new hot water tank in the airing cupboard has been carried out using a kind of metal putty to join copper pipe to the lead pipe. Can anyone please advise on how best to joing these 2 pipes together as at present complete replacement of the lead pipe is not an option.

Steve S
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Hi Steve. I could be wrong, but what you see as 'metal putty' is in fact the result of a plumber wiping a joint using lead and a blowlamp. Making and wiping a joint between lead pipe and lead pipe or lead pipe and copper pipe was an everyday occurance many years ago. Of course like most things you needed the correct preparation, the correct equipment and the skill to melt the filler lead without losing it. I'd certainly go along with masona suggestion. I assume there must be a rubber 'O' ring that gets squashed a little to make a watertight joint on the lead pipe side.
:rolleyes: :rolleyes: :rolleyes:
take a peice of the lead with you led locs are sized by weight
ie 6lb 7lb 9lb
if you take a peice of the pipe you will get the right one :D
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Thanks for the info gents, I actually got a look at a lead-lok today at a plumbers merchants. Does the weight size co-incide with the lead pipe diameter. If not, how is the weight sized ?
Thx what is the difference between the different 'weights' of lead-lok? I can only think it maybe the strength of the compression.
a foot of 6lb lead pipe has a different (smaller)diameter to a foot of 7lb lead pipe.
Ref lead pipe 7lb equates to 1/2 in. 9lb equates to 3/4 in according to builders merchants web site. I assume this will be inside diameter.
:rolleyes: :rolleyes: :rolleyes:
Yup, take a bit to the merchants and they should do a lead compression joint to copper. Failing this it's quite east to attach copper to lead, some people make it sound too difficult, is an art, etc... Just ream out the end of the lead, allowing the copper to to go inside about an inch. buy some solder, make sure inside the lead pipe and the end of the copper pipe is clean, flux them then insert the copper. heat the copper slowly and apply solder near the top of the joint, allowing it to fall into the gap, should remain quite liquid. Keep applying the solder until it reaches the top of the joint. Allow to cool... Done this on two mains feeds and a further gravity feed. No problems..

However this only works if if your joining a vertical length upwards from the lead. Horizontal or downwards, use the compression joint :D
I think I've done those most ways up, and can't remember having any problems with any. Technically illegal to do it on a mains supply, because of uncovering that nasty lead. :rolleyes:
Technically illegal to do it on a mains supply, because of uncovering that nasty lead
????? Why ????

My mains came in on lead went throught the cupboard under the stairs without stopping and arrived at the tank in the loft... all cold water feeds ran from the tank, including the kitchen supposedly "drinking water" :eek: Soon diverted that ;)
As I said, you're exposing fresh lead to the water by soldering it. Old lead pipes are covered in scale which practically stops dissolution of the metal.

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