As far as I can see the earth is simply a cable bonded to the incoming cold water pipe - just before the main stop tap. There is a copper conductor that runs from this bonding to a block near the CU. All the earths from ring mains etc meet there. I can't find any other incoming earth with the supply cable(s) ie from the elec. suppliers. The house was build in the 50's and has not been rewired! Is this a TT system? thanks.
Is this any help:
Most probably the water pipe is the earth! That's how it was done in the olden days. If it was my house I think it would be time for a complete rewire. I'm sure there would be plenty more problems you could find that would certainly condemn it.
SJW A.C.S. Ltd.
Sounds like a non-compliant TT system (it may have been compliant when installed, I don't know). To fix it, you need to add an earth rod and an unbroken cable between it and the earth block. Then add a 100mA time delay RCD to the entire system and ensure that socket circuits and other high risk circuits are on RCBOs, or the RCD side of a split load consumer unit with
30mA RCD.I would also check your main equipotential bonding. It you've got gas or other metal services, these need to be bonded too. Do any new main equipotential bonding in the sizes specified for TN-C-S, so that it is an easy upgrade if it becomes available. Skimping on cable and then doing it again in five years because the cable is now too small is not a good idea.
Christian.
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