No smell of gas, but 3.4mbs drop on a gas meter. Action needed?

ming60

Hi All. We have recently had new SMETS2 smart meters fitted by Octopus Energy. The fitter then tested for any gas leaks, and found a 3.4mbs drop on his meter. He said it was within the acceptable limit, and left it up to us to get it sorted or not. We have 3 appliances, a gas boiler, cooker, and gas fire. I can't smell any gas. I got our usual gas boiler service engineer round to do a test, and he couldn't detect any leaks from the appliances. He suggested the leak could be from the original pipes, somewhere under the floors! The house is 50 years old with some concrete floors. He quoted £1200 for fitting new pipework!

Do I have to have the work done immediately, if at all? 

Do I get a second opinion?

What is the current approved tolerance level for a gas leak, thus avoiding any immediate remedial work, < 4mb ? I've read that there seems to be various acceptable levels relating to different meters used to do the tests. I don't know what meter was used to do the measurement.

Thanks for any advise. It would be much appreciated.

Netexporter

The pressure drop doesn't mean there is a leak, as long as the pressure is static, it is a result of resistance to flow in the pipes. If there was a leak, the manometer would have shown a falling value and the engineer would not have passed it as safe to use. As long as the pressure drop is within limits then there is nothing to worry about.

Mr.Generous

The drop measured is the drop at 20mb pressure over 2 minutes, so it is a drop, a tiny one, but a drop in pressure indicates a leak. There are allowances in the regs for up to 0.5mb drop in 2 mins after the pipes have stabilised at the higher pressure. The most likely place for a weap is at a connection, and the easy one's to check are at a gas hob, a gas fire and at the boiler. Worth getting these checked by a gas man, very easy to check because every item connected can be isolated and then leak detection spray used.

Seasalt3

We had the same issue today!   Gas safe fitter came to do a safety inspection on our  cooker hob.  He tested the gas meter and said there was a small gas leak with a 1mb drop? .......Think thats what it was......  He said it was within the acceptable limit as long as we couldn't smell gas.  I wasn' t happy to leave it so he checked everything and couldn't find the source of the leak, so isolated the gas to the cooker and tested again which came back as normal so obvious it was the cooker.  He checked the pipework at back of cooker again  and tightened a joint on the pipe. He tested again and all normal.  It freaked me out to be honest as don't understand how it happened but if I was you I would want find out the cause for peace of mind and safety 




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ming60

Thanks all, for your interesting comments. However, I would still like to know what the upper mbar limit is of the "acceptable limit" mentioned.

Mr.Generous

ming60 said:

Thanks all, for your interesting comments. However, I would still like to know what the upper mbar limit is of the "acceptable limit" mentioned.

Found it:

Tightness test with a G4 Gas Meter: Ensure that the U-Gauge doesn't drop by more than 4 millibar from 20 and check for smell of gas.

Tightness test with a E6 Gas Meter: Ensure that the U-Gauge doesn't drop by more than 8 millibar from 20 and check for smell of gas.

ming60

I've just remembered that when the Octopus Energy guy told us we had a leek, he said it showed a 3.4mb drop, which he said was only a ⅓rd of the maximum allowance of 11mb. That seems a high upper tolerance limit, from what I've read. Is this correct?

mmmmikey

Hi, not sure on the exact figures but from what you've said it doesn't sound like there's anything you need to be unduly concerned about. Invariably these tests / approved limits err on the side of caution, for obvious reasons. But if you're like me and this kind of thing plays on your mind then any Gas Safe engineer can do a gas tightness test for you and establish where the gas is being lost. It might be as easy as tightening a fitting somewhere, but if not you can then make an informed decision as to whether to have the pipework replaced or whatever. Perhaps you could just bring forward your next boiler service and have everything checked at the same time.

Edit - whoops, sorry, I've just re read your original post and can see you've already done what I've suggested, in which case if it was me I'd have the pipe replaced on the grounds that if not I'd be forever worrying about it.

jefaz07

ming60 said:

I've just remembered that when the Octopus Energy guy told us we had a leek, he said it showed a 3.4mb drop, which he said was only a ⅓rd of the maximum allowance of 11mb. That seems a high upper tolerance limit, from what I've read. Is this correct?

Not sure where the 11mb figure has come from, but it’s not right. 

If a low pressure installation then the allowances are either 8mb or 4 mb for a E6 or G4 meter, testing at 20-21mb. That is with pipework 28mm or less in diameter. 

If your pipework is >28mm up to 35mm then those figures drop to 4.5mb and 2.5mb. 

If there is a smell of gas or no appliances are connected to the installation then there has to be no perceptible movement (no pressure loss) on either type of gauge. Perceptible movement being .25 on a water gauge and .2 on an electronic gauge. 

ming60

Thanks for all your very interesting replies. Much appreciated. However, I'm still yet undecided about going ahead with having new gas pipes.
To help with any more replies, the smart gas meter that has been installed is a Landis + Gyr G470.
I don't know if this has any bearing on the allowances that have been mentioned in some of your replies above, as they refer to E6, E8, and G4 meters, which I think are the old type of meter, that has now been replaced by the Landis electronic one.
As we have floorboards, and airbricks, where probably 75% of the pipes could be laid, can I assume that the small 3.4mbar gas leak (no smell) we have, could be dispersed enough under there, not to be a problem?

jefaz07

ming60 said:

Thanks for all your very interesting replies. Much appreciated. However, I'm still yet undecided about going ahead with having new gas pipes.
To help with any more replies, the smart gas meter that has been installed is a Landis + Gyr G470.
I don't know if this has any bearing on the allowances that have been mentioned in some of your replies above, as they refer to E6, E8, and G4 meters, which I think are the old type of meter, that has now been replaced by the Landis electronic one.
As we have floorboards, and airbricks, where probably 75% of the pipes could be laid, can I assume that the small 3.4mbar gas leak (no smell) we have, could be dispersed enough under there, not to be a problem?

Sorry, I incorrectly typed E8 instead of E6…which is the correct size. 

You have an E6 meter so an allowance of 8mb. 

The first 2 digits of the meter serial number will start with E6?

And yes, the 3.4mb gas escape is well within tolerance so shouldn’t be a problem. Some people want it sorted, some people leave it. But as per the gas regs it’s perfectly acceptable to leave