Tim (Remove NOSPAM. wrote:

What if incoming water pipe is plastic? (no oil or gas) The Earth rod is
then sufficient??

No - if all or most of the house pipework is in copper (or other metal,
naturally), then that should be bonded to your main earth terminal close
to the transition from plastic-incomer to copper-internal - usually
this'll be at your internal stopcock. The idea is that the bulk of the
metal pipework in your house should provide a low-resistance path for
any fault current: that way, if some fault (e.g. in a hot water boiler,
immersion heater, or less likely misplaced nail
touching-but-not-severing L-in-cable and going on to a water pipe - I
said less likely, OK!?) brings your supply Live into contact with that
pipework, (a) a big enough current will flow to make any fuse/MCB pop
nice and quickly, (b) even while the fuse/MCB is deciding how quickly to
pop, the pipework doesn't rise to a voltage far above earth (cos the low
resistance of its connection to earth means most of the 240V is dropped
on the L side of the fault).

But if your pipework's all or nearly-all plastic (e.g. just visible
copper tails going to radiators), there's no need to bond the short
segments of copper pipework.

HTH - Stefek