Bonding Lead Water Pipe

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m4tty

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Hi,

Ive got to bond the water pipe but its a lead pipe. It already has old copper clamps (you know, with a series of bolt holes) with a 7/029 hanging (as per picture posted in other thread) Is this ok to bond with BS951 clamp. Do i need to clean the pipe to show new metal to ensure good continuity.

Sorry for the basic question but its new to me so I want to know how to do it properly.

Thanks:put the kettle on

 
dont bond the lead - itll squash the lead, and could end up a loose connection, or start a leak. best to bond at the first bit of copper, and note on cert

 
lol Does take a bit of heated persuading with their clueless customer service staff but I have managed to get them changed on a few occasions.

Pigs flying would probably be easier to achieve tho!

 
As the others have said, M4tty, we are not supposed to put clamps on lead pipes and if its all lead we are supposed to get a plumber to insert a piece of copper to take the clamp.

 
Sorry if ive asked this already but memories not too good. If I use 16mm MEC to rod from MET. What size do the MPBC need to be? 10mm or should I just use 16mm for both.

Thanks

 
I had seen some tests on the web of a BS951 clamp on a lead supply to a domestic property, so i carried out my own. It didn't matter how tight you did up the screw, the pipe did not collapse or appear to diminish in diameter. However i suppose it may bite into the lead over time and become loose.

I have placed the clamp on the first union nut i could find, sometimes the stopcock, sometimes a T. A few times when there has been no other way i have placed it on the lead pipe and noted it on the cert, well tar & feather me & hang me out for the wolves.

 
when there has been no other way i have placed it on the lead pipe and noted it on the cert, well tar & feather me & hang me out for the wolves.

Yep ! Slipshod Mate. Im with you on this one....its known as living in the real world.

 
S&S,

You are correct that with the minuscule vibrations that will occur in the lead water pipe over time, the clamp may indeed deform the pipe under what is known as cold flow deformation.

HOWEVER, this phenomenon also occurs in solid copper conductors when clamped into screwed connectors.

This is one reason why the wago type spring loaded connectors have certain advantages.

From a mechanics/materials standpoint, it would be possible for the clamp to work loose.

The timescale would be predictable after heavy analysis and loads of number crunching.

Probably at a first guess greater than the 10 year span between PIR's!

Electrical connections when secured with screws are at greater risk from deformation from cold flow as they are also subject to temperature fluctuations, the magnitude of which is unknown and depends on the actual circuit loading.

As the conductor heats up it expands, this expansion is constrained by the securing screw, however, the larger volume of material has to go somewhere, so it expands to fill any voids in the connection.

When it cools, it is no longer constrained, thus it can contract equally in all dimensions, thus it will get smaller under the securing screw, this can go on for several cycles depending upon the amount of elastic deformation that has occurred in the connection terminal when it was tightened.

That is how much spring is in it.

Once the material under the screw has shrunk away from correct contact then you have a loose connection.

How often does this happen in actual fact in an electrical screwed connection such as at the back of a s.o. or light switch, or in an MCB or RCD?

This should give you an idea of the likelihood of cold plastic deformation of a lead water pipe!

;)

 
Ahh,

OK good point, however, that brings in another variable which was not the point of my post.

Let us say then for a correctly made termination, which we would all obviously do!

The failure mode in your example would not be due to plastic deformation of the conductors, it would be due to the termination being inadequately secured in the first place.

 
Earthing on a TT system is different to a TN system. The expected fault currents and the cables capacity to hold this fault and get rid, as it where, means that for a TT installation 10mm or even 6mm main earth is ok under the regulations.

Most people however I included like to beef up the cables and use 16mm and 10mm.

 
Yes thats right m4

See OSG Pg 29 Table 4.2

If the MAIN EARTHING LEAD IS BURIED then it should be 16mm but if its protected in a conduit it can be 2.5mm!

If not buried it can be 4mm or 2.5mm if in conduit.

THE REASON IS unlike a TN system the TT system with RCD protection does not carry large current to enable the device to operate and as the Earth stake resistence is going to be fairly high the resistence of the earth LEAD is not going to add a lot to the total.

 
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