Flooded gas pipes

Recently I have seen on the news households without gas due to burst water pipes that have flooded gas mains. I am confused as to how this happens unless the gas pipes have also ruptured, even then I would have thought the gas pressure would keep the water out. Any ideas?

Was it the actual gas main pipes OR just that the washed away ground that left the gas pipes in an endangered state?

I can still remember when I was a child the local gas works coming round and pumping water out of the gas pipes in the road. It used to stink for days as they left it in the gutters. Late forties.

There was a video on the news of water pouring out of a gas meter pipe so water got into the gas pipes. The old iron gas pipes are being replaced around the country with plastic pipes because the iron pipes are cast and so very brittle. Water mains are at a higher pressure than gas so if there is a water leak that is either near a broken gas pipe or washes away enough soil to cause a gas pipe to collapse then the water will pour into the gas pipe as its pressure is higher.

Given that this has happened when a lot of places are going to be using gas for heating I can only imagine there is a lot of work to be done to clear out the water from all the appliances that have been flooded with the wrong fluid.

Martin C

Quick Google got me What Is The Pressure Per Square Inch (PSI) Of Natural Gas In A Home? (homeupward.com)

This suggest that the pressure in the final leg of the supply is measured in inches of water (1/4psi). So a gas pipe buried a few feet down subject to a foot or two of water would not have enough pressure to resist.

Doesn't answer the question of how or where it got in - there must have been a weak spot somewhere.

On TV they showed a fitter (sorry - engineer) pouring water out of a smart meter, so it was definitely in the gas main.

The process of putting in plastic pipes is basically the iron pipe is either cut or smashed with a hammer and the plastic pipes fed through the old pipe. Holes are dug outside each property to connect them to the new pipe and put plastic pipe through to the meter. This will often require a hole to be dug in the area near the meter as well. For some households the meter will also be moved to the outside for free if it suits the owners needs and wishes (happened to my neighbour). I had plastic pipe already dating back about 20 years due to an extension being built so the old concrete patch was dug out again in the pavement to connect my existing pipe to the new main. The new patch looks a lot better than the old one.

Martin C

This has recently occurred in an area of Sheffield. A water main burst and due to the pressure of the water it penetrated gas pipes that were running close to the water main. Water was reported to be coming out of domestic gas appliances.

A couple of years ago houses in our close were experiencing supply problems with the gas, a crew turned up and connected with the gas main through an access point in the pavement and proceeded to pump out water that had accumulated in the gas main, apparently there are access points in gas mains at strategic points purely for the purpose of pumping out accumulated water, this is different and unconnected to the emergency problems that are occurring currently in Yorkshire. Our Close has since had the gas mains sleeved internally with plastic so not sure if water accumulation will occur again. Dave W

The pressure before all domestic meters is much higher than afterwards - they are a pressure regulating device as well as a meter. So your post is irrelevant for any external gas pipes before the house. I’ve no idea what the street pressure might be.

I hadn't heard of this phenomenon before, so, out of curiosity I 'did a Gilligan' and found this: www.gasinfo.uk.com/Distribution_page.htm

I used to make the tooling for the new plastic tubing and fittings which are now installed to replace cast iron tubing and fittings. In certain places cast iron is still used i.e. across rivers for instance and some pipe grows after installing inside the old cast iron pipe with the gas pressure which is 22mb usually. There is also some plastic pipe which has a metallic ribbon inside the plastic which can be used as a network cable. The pipe is tested to 10 bar in laboratory set up and in one test is that it is ripped out of the ground with a JCB digger bucket without rupturing or losing pressure. The fittings have a heating element built in during manufacture which melts the joint and fixes the fittings when cooled. The house tap is pressed onto the larger area pipe and clamped whilst welded on then the pipe to the house etc is put in and also welded to branch spigot. Then a cutter type piece is screwed down to cut the gas exit hole to the house this collects the disc cut from the main pipe and as unscrewed acts as a tap for the house supply and can be used to turn on and off the supply if necessary.

David

My previous home town, and a serious problem for at least 2000 households.
Essentially the water main burst up at Stannington, one of the highest parts of that side of town.
The force of the burst was sufficient that it ruptured the adjacent gas main.
Since it was underground, the water pressure then filled the broken gas main, and ran both up and mainly downhill.
Water has now filled the main gas pipework in the area, as well as consumers meters and appliances; boilers, fires, ovens, etc..
The last time I read up on it, Cadent had pumped out 700,000 litres of water from the main and were far from competing it. The various gas engineers have been highly praised locally, but it's a real issue when there are reports of 90+ year old folk without heating, bathing, or cooking facilities.
Some folk have been re-connected, having had their meters changed, and appliances cleaned and drained, but others are still without gas a week later.
The local MP has spoken up in parliament, requesting assistance, and a formal major incident was declared.
Lots of local news reports, this is just one example
https://www.yorkshirepost.co.uk/news/stannington-people-left-without-gas-for-a-week-in-freezing-temperatures-remain-resilient-3947702
https://www.trendsmap.com/twitter/tweet/1600509388049244161 

It looks like Cadent are working hard to mend the gas side of things, and have distributed emergency electric heating and cooking appliances, but apparently this has now overloaded the local electricity grid.
https://www.theguardian.com/uk-news/2022/dec/07/sheffield-residents-face-fifth-day-without-heat-after-gas-mains-flooded 

Bill

Edited By peak4 on 09/12/2022 23:00:29

Edited By peak4 on 09/12/2022 23:05:09

Still ongoing by the looks of it.
https://www.theguardian.com/uk-news/2022/dec/11/sheffield-flooded-gas-pipes-snow-delays-restoration

I'm due out for lunch with a couple of ex-workmates, who look like they were/are both affected, so no doubt I'll get all the details them.

Bill