Great, a gas leak...

[v12bug]

hi guys,

Allow me first to say what an absolute superb website this is! The guys on here really know their stuff, as I've been an avid reader for sometime... Anyway, my first post, is unfortunately not a good one..

Over the last few days I started to notice, on and off, a very small smell of gas, coming 'only' from where the gas meter is installed. (underneath the stairs).. So, I thought I better check it out..

So, I first did some basic checks before calling out Transco.. I isolated the Vaillant Boiler, by turning it off and closing the Ball Valve underneath. The gas cooker unfortunately does not have an isolator.. Anyway, I carefully watched the Gas Meter over the next hour or so, (obviously all gas appliances off) and sure enough it was moving very very slowly, roughly '5 little notches' on the meter over the hour (the indicator furthest to the right).

SO, I called out Transco, and the guy confirmed there was a 'pinhole leak' somewhere. He said it was dropping around 3/4mm? over 2 minutes. He decided to change the meter, which was quite old, just in case.. and then proceeded to use a sniffer and some soapy water! Unfortunately the leak was still present, and he could not detect any leak around the meter. He said although the leak was not that bad (boarderline tolerances?), as I reported that I had smelt some gas, he had no other option but to capp the supply!! His conclusion was that it was most likely to be the copper piping between the meter and my boiler.

Now, the cooper pipe goes into the floor, which has been secreeded over (under floor heating), but I realise that there is no pipe lagging around the pipe where it comes up through the floor, although I denfinately do know there is lagging on the pipe under the floor. Would the secreed have caused the copper to corrode or something similiar where it touches it on the sufface? My underfloor heating and boiler are only 7 months old, and I have never smelt any gas previously, all through winter in all.

Lastly, when commissioned serveral months ago, it was pressure tested, and there was 'no drop' at all.. got a Gas Safety Cert as well, from the Corgi guy, (who is conveniently on hols till next Monday)

What's the best course of action / suggestions? Thanks all

 

[doyle]

some corgis will/might ignore a 1mb drop unless gas is smelt as it could well prove hard to find without capping each individual pipe .

now its capped off you need to have it recified before it is uncapped again.

the only way to find it is disconnecting appliances and caping of pipes unless you have tools to find it. as it is within the house where you smell it then the gas escape is not going to atmosphere making high risk not to have it rectified.

 

[v12bug]

thanks for your reply.. although the Transco guy could not smell it whilst he was here, like I said I can smell it ever so slightly now and again.. which will mean finding the pinhole leak could prove an issue.. I guess the cement secreed and copper piping, wouldn't cause this then?

btw, I forgot to mention when I initially was doing some basic tests, I switched off the main supply for about an hour, then whilst turning it back on, I heard a 'hissing' sound (like a rush of gas, most likely) coming from the meter, for a few seconds, is that normal? Shouldn't it be silent, when turning it back on?

 

[Garfeild]

You will get a hissing sound from the regulator,its only the diapragm inside moving.
Can you surface run a new pipe bypassing the leaking part which is buried?

 

[doyle]

thats normal, what i think is happening is the escaped gas is building up, when you open the meter cupboard ect the gas is released to atmosphere hence why you smell it every now and again and he didnt.

another possible could be their is no leak on the pipes and what you are smelling is build up of unvented damp area below floors that can be quite pungent at times and reduces when vented( this happens at mine had transco out no leak detected with sniffer pungent smell not to disimular to gas) the gas leak detected via the monometer on the meter turned out to be the cooker gas taps, rectified by closing the lid and reading altered again. however their was no possible way the gas from the cooker knobs could have gone below the floorboards through two walls an dinto the meter cuboard if you know what i mean.

something you can do is get some leak detection fluids and spray any suspect area on pipes and joints, it may show a leak or might not as it is small, around the bayonet to cooker and what not.

if you find it then jobs a good one but if not dont worry the gas fitter you call will find it no problem.

 

[v12bug]

Well, the smell is definately not down to being in a meter cupboard, as underneath the staircase, it's all open.. even the gas meter isn't housed, as yet! And as for the flooring, the entire ground floor has been screeded / tiled, floor boards removed! (for under-floor heating). So the smell cannot be coming from there. I just hope to god that it's not the copper piping between the meter, and the boiler, which is situated in the kitchen! So, a surface run, is really out of the question, as its a bit of a distance, across our living room!
Having said that, the pipe was tested when installed and there was no pressure drop several months ago.. so I can only think maybe the copper pipe coming out of the meter into the ground has sustained some kind of damage? or maybe slightly corroded because of not being lagged when going into the screed at that point.

btw, you mentioned 'some corgis will/might ignore a 1mb drop unless gas is smelt..' by that I am assuming that I've got a 1mb drop? Just out of curiosty is that the same term as used by the Trasco guy, when he said 3/4m? per 2mins??

 

[Gasguru]

You are permited a drop of up to 4 mbar over a 2 minute period (assuming you have a standard unitary meter and not the smaller ultrasonic type meter) PROVIDED you cannot smell gas and the leak is not on the pipework. In practice most occupiers can often smell a leak of only 1 mbar.

The "Transco" engineer would have capped the outlet of the meter and then carried out a tightness test to determine if the leak is on their side of the installation or your side of the installation. It appears the leak is downstream of the meter outlet. Although the drop may be within the 4 mbar limit since you could smell the leak he had no option but to cap the meter off.

Why don't you contact the original installer. The next step would be to isolate the gas supply to the boiler (at the boiler gas valve) and disconnect the cooker at the hose connection on the wall bayonet fixing. It can easily be determined if the leak is then on the pipework or appliances.

Most leaks are easily found within a few minutes with a suitable gas sniffer instrument.

 

[Rob]

No the maximum is 4mb however it should still not be ignored.

Its easy to prove where its coming from by capping stuff. Firstly the meter, if it holds you know its after the meter if it drops with appliances off then it can only be on the pipe work.

Might be worth paying a corgi engineer for an hour to try and trace the leak.

edit: what he said ^^

 

[v12bug]

thanks Gasguru / rob / doyle for that explanation / tips.. well I don't blame the Transco guy all at for capping off the supply, even as doyle said, although I have a drop of only 1mbar, you correct point out that I can ever so slightly smell this. So obviously I would want this fixed in any case.. I just cannot believe this to happen on a completely brand new install.. new copper piping everywhere, and checked, when completed!

Anyway, as I am a curious fella / don't want to sit on my backside twiddling my thumbs, I have just bought a "pH Gas Fluid Detector" which is suppose to show foamy / bubbles, in the event the fluid finding a leak on the pipework, so I will give this a try, on the pipework I can see, until the Corgi chap who installed the system comes around next week.

 

[doyle]

4 mb on on existing installation appliances your allowed nothing on pipes especially after report of gas escape.

i have 2 mb drop on appliance with no smell of gas if i could smell gas then im allowed nothing zero mb, the 3/4 mb you talk of over two minutes is the tightness test which you are allowed a max of 4 mb over two minutes with no smell of gas. this is for appliances again pipe work your allowed nothing, however its reported a gas escape and needs remedy.

if you call a corgi he/she will simply cap of the pipe to see if that pipe is leeking if it is then run a new pipe or repair the existing, bing bang bosh.

their is no short cut around it im affraid you need to call someone out to rectify the problem.
the sniffers used are v sensative so if leekage is in that area the transco guy would have found it. if they cant find it who else could, so its on the system some where else.

 

[gas4you]

Was your copper gas pipe in floor coated with yellow plastic?

how are you going to check for leaks with your test fluid if the gas has been disced at meter I take it you haven't removed the disc yourself

 

[v12bug]

gas4you, the copper piping in the floor screed was covered all the way, with pipe lagging.. although they did not do the little bit of copper pipe where it comes up from the ground to the meter.. Are you talking about the yellow gas flexi pipe.. that I do not have installed. Would that have been a better solution then?

..oh yeah.. I can't test for leaks, can I, not until the meter is un-capped.. what a dufuss. Doesn't matter, I can wait until next week..

Microwave meals are getting more healthier nowadays, anyway.

 

[Bahco]

Another strong case for NOT burying pipes be it gas or water.

 

[gas4you]

All gas pipe (copper) in floor screed should be kuterlux plus copper. This is copper pipe coated at the factory with a yellow plastic coating that has air gaps in it to act as a sleeve.

Not many installers use this but it should have been at least the basic yellow coated plastic pipe and not just covered in pipe insulation. This could possibly explain the leak and smell after such a short time

 

[v12bug]

yeah you're right.. beginning to wander if it was all worth it! With underfloor heating, what else can you do? I mean my entire ground floor was ripped up and then concrete screeded and tiled, with the under-floor heating pipes running every where.. I am just thinking about what Dave said.. maybe I would have been better off getting the guys to run the 'yellow gas pipe' in the screed, rather than the copper piping.. still don't get how a leak can occur though after several months..