I would welcome your views on this one. Please stick with me as I try to adequately describe the situation. I've just fitted a new Consumer unit in the garage as a replacement for my old semi rewirable one. I have fitted a 10mm earth cable from the Main Earth Terminal to the Consumer unit earth block. A separate 10mm earth cable runs from the copper gas pipe (within 600mm from entry) to the Consumer unit's earth block. The plastic water service feed pipe is about three metres from the Consumer unit. The plastic pipe becomes a 15mm copper pipe before passing through the water meter. Aside from the earth clamp and cable to the meter there is no sign of the water main bonding strap. The water pipes pass through the wall into the house at this stage. Back at the Consumer Unit a third 10mm earth cable runs from the CU earth block to the Central heating boiler water pipes where it runs unsheathed but unbroken through an earth strap and off across the garage toward the incoming water pipe. The earth cable then disappears into a wall 'seemingly' to meet up with the water pipe inside the house. Lets call that the 'hidden cable' I have done R2 continuity checks with the two visible earth cables and got acceptable very low ohm readings. I obviously cannot do the same with the third hidden cable but I decided to do a wander lead test between the CU end of the hidden cable and the copper pipe near to the water meter and found a very low ohn reading 0.005ohms. Despite this reading I do not think it is acceptable for the bonding strap to be hidden from view. I therefore intend to fit a new bonding strap and 10mm cable to the incoming copper water pipe and run it back to the CU. My key question is whether it is permissible to run the water earth cable from the water pipe back through the Gas boiler water pipes (which is clearly supplementary bonding) onto the CU.