On Tue, 2 Oct 2012 21:22:01 +0100, Piers Finlayson
wrote:

4.5 years into this house I discovered that the downstairs shower was
wired from the upstairs ringmain. I'm glad now we never used it, and
that I only found out because I was removing it (and I'm also glad I
carefully checked it wasn't still live after swicthing off the "shower"
mcb).

About ten years back I sorted out a shower in a rear extension. Turned
out the previous owner was a handy sort of guy and built the
extension, did his own electrics and plumbing.
The 8.5kW electric shower unit was fed from a tank in the loft - so,
the pressure wasn't enough to activate it; this being a mains shower
the pressure-low switch had stepped in and done its job, disabling the
shower.
Which was just as well, really.
On examining the wiring I found the shower electric supply was run
from the extension, up the inside of the back wall, along the loft
floor and down two stories at the front of the house (down a bedroom
wall), to the consumer unit.
Instead of 6mm cable, the total ****ing arsehole that wired it had
used 2.5mm.
Imagine; if the shower had worked, that overheating cable stretched
the full length of the house just waiting to eventually set something
alight.

Oh, and one other thing - the shower didn't have its own RCB or RCBO,
(it had an MCB) it depended on the main house one. When I tested it;
it failed shut.