In the past, it was common to connect the earth wire (green/yellow wire) of an appliance to the water pipe. But now we were told to connect it to the earth pin of the power plug, instead. But, why can't we use the water pipe anymore?
Currently, I am installing a new electric heater but have to reuse an old power cord that runs through the wall that has only 2 wires (line and neutral) without the earth wire. So, it is impossible for me to connect the heater's earth wire to the earth pin of the plug. I am thinking of using the old method of using the water pipe to earth my heater. Is it a valid method? Another possibility is to connect my heater's earth to the earth of another appliance nearby. Does it make any difference?
We are following the UK electric wiring standards although strict adherence to the standard is not my concern.