[ms660]

Sometimes in older property copper pipe is a replacement for the old bsp galv. pipe, usually the rest of the old pipe is buried underground and is usually in a very poor state if it is the original and probably would not make a decent signal earth.
It is true to say that bonding should be at the nearest place to the board as already mentioned with other bonding at the appropriate places, assuming that there is a continuity of the copper/...s/steel pipe, quite often there is not in these days of push fit plastic and diy alterations.I have "heard" that sinks do not have to be earthed if fed by plastic pipe ? DO NOT QUOTE ME ON THIS!!
Always best to check with current regs. as they are changing so fast
Hope this is of use to someone.
Cheers.