"Mike Clarke" wrote in message
o.uk...
On 27/12/2010 20:26, Fredxx wrote:
On the other hand ice is more resistive than water, so any current you
can pass into the stopcock will largely heat only the plugs of ice.
Assuming the plug of water the other side is earthed somehow! It might
also be a good idea to isolate the internal piping first.

No chance of getting an earth through water in a plastic pipe if it's more
than a metre or so long.

--
Mike Clarke

What sort of "earth" are we talking about? What sort of current would pass
at a few kV? In practice it would depend heavily on the purity of the
water. My comment is that the resistivity of ice is even higher, such that
all the voltage, and hence power, would be dropped across any plug of ice.