On Sun, 09 Sep 2012 20:04:19 +0100, (Alan J. Wylie)
wrote:

Graham. writes:

The last 3 or 4 times I have visited them I have heard a thud, and the
lights blink at the same moment. This happens maybe twice per hour,
but not regularly enough to be able to predict the next event.

...

The bangs however seem to emanate under the floor at the back of the
house near to, or maybe even beyond the party wall. The elderly lady
next door says she hasn't noticed anything.

I thought water would be involved, and we have had torrential rain
recently, however not a drop has fallen this week and I witnessed 3 of
these events last night.

...

I had exactly this problem 20 years ago soon after I moved in to a house
I had just bought. The bangs seemed to be days/weeks apart, though

Eventually diagnosed to a blocked underground watercourse running
through the front garden, water coming in under the floorboards, and
some plonker having left a dangling unterminated live mains cable
lying on the rubble under the floor. The end of the cable was clearly
split and blown apart. I still haven't worked out the exact mechanism:
mains is A/C so electrolysis producing hydrogen shouldn't be the answer.

I suppose AC electrolysis of water gives two parts hydrogen and 1 part
oxygen from *both* electrodes. I wonder if that is the mechanism? It
does sound a bit like percussive gas ignition. Earlier I suggested it
might be due to superheated steam.


--
Graham.
%Profound_observation%