Earthing strap on water supply

Homersimpson

The purpose of earth bonding is to ensure that there is no potential difference between electrically conducting objects. This is the same principle as birds sitting on HV overhead lines, if the electricity doesn't want to go through you because you arn't the path of least resistance then the actual voltage present is irrelevant.

For information the resistance of the average person is around 1000ohms but obviously this would vary based on the size/weight of the person.

Whilst under the 17th edition you can get around the need for supplimentary bonding by providing RCD's on all circuits, the provision of supplimentary bonding does not have a detremential effect in these circumstances.

If it were me I would cross bond the pipes at all sinks (and to the sink itself if metal) and I would bond the bath (if its metal) to the earth on the shower (if its electric) and the shower pipes and bath pipework.

I would cross bond all of the pipes from the boiler to the earth on the boiler supply. The one exception to this is where you have a single fitment tap i.e. a mixer tap and a ceramic sink in which case I wouldn't bond anything as you only have one point of contact.

I would use 4mm2 green and yellow cable for all bonding as a minimum.