"nightjar" wrote in message
...
On 17/10/2020 18:21, NY wrote:
My parents were one of the 400-odd houses which lost their gas supply
near Aylesbury when a water main burst (which quite an explosion, from
witness reports) and fractured an adjacent gas main, letting water in the
gas main. Apparently the water caused stones in the ground to be
circulated by the cascading water, abrading a hole in the gas pipe. There
have been "lots of" gas vans parked up, as they try to empty the water
and restore gas supplies.

But how do they go about emptying out the water from the pipe? About 1.5
miles of pipe are affected - the houses that have lost their supply
extend about 3/4 mile either side of the burst.

Gas dewatering equipment :-)

AIUI, this is an air or nitrogen powered venturi pump that sucks the water
out into a water trap.

So is that the real reason that all the houses' gas supplies have to be
turned off? Not just for reasons of safety but because the dewatering
equipment *requires* a sealed pipe (far end and every branch to a house) in
order for it to work? How does it cope with a gas main that may not be
completely level and so may retain water in the "troughs"?

The good news is that my parents' gas supply was restored this evening after
about 48 hours without heating or cooking - other than the electric fan
heater and cooking hob that the gas company *gave* my parents (COVID
cleaning and quarantine rules mean that it is more trouble than it is worth
to take the equipment back after the gas supply has been restored). And
their neighbours who have an electric oven rather than gas said they'd cook
a bit extra roast lamb and give it to my parents - community spirit is still
alive!

Mum and Dad got talking to the people from the gas company and found that
engineers had been brought in from all over the place as, far away as
Exeter, and there were vans as far as they eye could see parked all the way
along the layby along their road.

Are there ever cases where water gets into a gas main and the pressure of
gas forces it out of appliances - eg out of the burners of your gas hob or
boiler? ;-)