There has been many cases reported that people have been fatally electrocuted while bathing and the blame was put on the instant water heater that they have been using. As a guy who has been in contact with the electrical trade for more than 20 years, I don’t think the actual culprit is the water heater itself. My opinion is it is due to sloppy workmanship when installation of the water heater or when installation of wiring the heater point were carried out.
Installing electrical outlets, be it for a water heater point or whatever has certain unwritten rules that must be observed. Not only will the job looks neat, it will also be safer when it comes to installing something that needs the wall to be drilled later on. All wires MUST be run in a straight line downwards from the ceiling. There should be no wires running horizontally lower than one or two inches from the level of your ceiling. Electricians should discuss with the workers who installs the ceiling to find out where they intend to nail their beams and so on.
When installing items like wall lights, Air Con units, water heaters or even when hanging up pictures after moving into a new house, all experienced electricians takes it for a fact that wires are run vertically downwards from the ceiling. For example if there is a socket point beneath, they take it for a fact that the wires are run vertically down in a straight line from the ceiling. So when they have to drill, they will avoid drilling around that area, lest they hit a live wire.
Trouble starts when unscrupulous contractors tries to save up on the usage of wires and run those wires horizontally along the walls. Then everything is out of expectation and it becomes extremely dangerous if you start drilling any part of your wall. You will never know if there are wires running underneath.
I have come across water heaters that leaks current every-time the bathroom walls gets wet. The funny thing is when the Heater is taken down from it’s mounting, all checks proved that it was okay. On checking further, I found that the mounting plates were “alive” when placed my test pen on it. Only then did I realise that the guy who installed the water heater had scrapped a live wire underneath the tiles when he drilled holes to screw on the mounting plate.
I don’t blame him. Looking at the heaters electrical point I too would not have expected that the wires to be running there. It was about 3 inches, horizontally away from the point. To prove my point to the occupant, I chipped away a piece of the tile and sure enough, the former contractor had took a short cut and ran the wires along the walls rather than going up the ceiling and running down the wires again in a straight vertical line. For the sake of saving up some wires, he nearly killed someone.