Gas in water?

[Brian Gaff (Sofa]

About three weeks ago we had a major water main burst which supplied a lot of the south of the borough of Kingston Upon Thames, Thames water bypassed the problem area somehow and although the pressure was lower then before, we all forgot about it till this last Tuesday, when the water went off mid morning without warning. Luckily it was only off for about half an hour and then came on with more pressure. One supposed that they have now reconnected the fixed main. However there are always air locks coming through after such work and this was no different and it lasted best part of that day to clear. The oddity occurred mid afternoon when I became aware of a smell of gas in my kitchen, I do not have any gas!

It seemed that when I filled the kettle the air locks had gas in them, but it obviously was not air! My question is, how can this actually happen? Surely when you get a main burst, it could damage other services like gas, but after all that time and with people repairing it how could gas get into water?

Brian

[Andy Burns]

See if you can set fire to your water, if so blame it on fracking, probably best not to ...

[Jeff Layman]

Well, if a high pressure water main burst it could have damaged a gas pipe near to it. Though how gas would then get into the water pipe after it was repaired is a bit of a mystery. I would phone the water company and let them know what you've found.

[Chris Hogg]

Was it actually 'gas', in the sense of mostly methane, i.e. inflammable, or was it simply smelly? If the latter, I'd suggest it was just due to the water having remained static in the pipes for a few days, allowing a smell to develop, or the water they used to flush the pipes with after the repair was a bit smelly.

[Nick Odell]

Further, what are the main gas pipes made of? To my untrained nose, ordinary air that's been trapped in a damp, cast-iron environment takes on a "gassy" smell.

Nick

[nightjar]

It is probably only the mercaptan that is added to gas to give it an odour that has got into the water, rather than the gas itself. Mercaptan is incredibly smelly stuff and can be detected in miniscule amounts; An escape in Rouen some years ago lead to reports of gas leaks as far away as London.

[Nick Odell]

Sorry, I meant, what are the water main pipes made of?

N.

[Radio Man]

AFAIK the mercaptan is added centrally not locally. I have heard of gas getting into water pipes after major damage to pipes in other countries but not in the UK. It is is possible but more likely Brian is smelling something else which he thinks is gas. Possibly they used something to flush a section of damaged pipe which had an unusual smell.

[Tim Streater]

Plastic, these days, I think. Not rigid, either, but slightly flexible so that it doesn't crack.

[Jim GM4DHJ ...]

seen metal filings in gas but only on the west coast of Scotland.....

[Brian Gaff (Sofa]

No way to tell, I'd imagine it was only trace amounts but they put the pong in deliberately I think to alert people. Brian

[Brian Gaff (Sofa]

Yes I did that but its all gone of course now so was obviously at some point in the pipe. I can see how it may have got in though as I've since heard that some of the gas pipes around that area are almost rusted through and only the clay soil is acting as a pipe, which is probably why all around this area they are replacing the gas feeds to buildings. If gas got into the clay it is, I think very possible it got in through the leak site as some debris saturated with gas and then when it was depressurised it eventually came out somewhere.

Personally I was quite appalled that the gas pipes could have been left long enough to almost rust to nothing before any got round to replacing them with plastic. Brian

[Brian Gaff (Sofa]

Well I'm not going to try to set fire to it am I? That would be dangerous! It was not the stagnant water smell, it definitely was the chemical used to make gas smell. I know what that is like as we had gas and I've been in close proximity to a gas leak under a footway quite recently while an engineer was trying to localise it. Brian

[Brian Gaff (Sofa]

Most of the old gas pipes around here were galvanised metal, but now look rusty and fool of holes.

I think I may have the answer in the leaky gas pipes and the depressurised main, but I suspect one will never really know. Brian

[Brian Gaff (Sofa]

In my street they pushed plastic pipes through the iron ones, except mine since I have no gas, they just put a stop end on the feed point, Somebody told me the plastic is a horrid shade of yellow where water is a similar horrid shade of blue. Brian

[Brian Gaff (Sofa]

Yes I think it might have got in when they initially turned off the water from the leaking pipe and the gas was already leaking through rusty pipework and clay soil kept it mostly still running but then as they excavated some bits oof the polluted clay got into the pipe as they fixed it and there you are, probably not much gas there at all, but that smell is designed to be pungent. I've run the washing machine since then and that certainly did not blow up, so one can assume all is well again. Brian

[Brian Gaff (Sofa]

No its not chlorine either. I think the original poster above got it right, just trace amounts and you smell it in a confined space very badly. It is obviously a gas in itself so probably has separated slightly from the methane. Interestingly, Calor and Gaz had slightly different smells if I go back to my caravan living days. Brian

[polygonum_on_google]

Not on a full high pressure main, but our branch of the gas main had a leak a few years ago. We had reported gas smell a few times over the years but, despite coming round with detectors, they decided there was no leak. Finally, a water leak resulted in digging. And they found something like half a dozen leaks from a failing iron gas pipe. Took forever as the water people waited for the gas people to make it safe, then the gas people had to wait for the water people to replace their pipe, etc.

Goodness knows how much gas they lost over the years. As it was the company's pipe, it didn't cost us anything, but what a waste.

[charles]

After a new (plastic) gas mail was installed in our road, we kept smelling gas. Turned oyt to be residual stuff in the old iron pipe being disolved in rain water seeping down.

[Steve Walker]

That's right. I once worked at a place that had two tanks, each holding

15 tonnes (IIRC) of liquified natural gas. When we were testing gas engine or gas turbine driven compressor sets, the liquid was piped into a boiler to gasify it and then the chemical smell was added.

It caused panic when, in the middle of the night, the smell machine sprung a leak and was spraying the raw chemical out - it was both very powerful and spread far and wide, leading to an emergency response for a suspected burst of a high-pressure main!