gas leak - within limits?

[bobs yer uncle]

All,
Perhaps this should be a fresh post or maybe it’s better posted on ARGI Anyway 4/8mb perceptible leak with appliances connected……
Can someone please explain to me why there is a 4mb drop allowed when an imperial (U6) meter is connected and 8mb with a metric (E6) meter. I went to college, I did my ACS and I see myself as more than competent. When this has been explained to me I have been told many different reasons. The most common being that the size of a metric meter is smaller and that it is more or less just a pipe with something to measure the movement of gas. When I have questioned the reasons the explanation usually ends up with ‘because it is’ Trouble is this does not make logical sense to me and it has just become something I accept. So my first question is explain the above…. logically, please.

The second part is this……
Take a hypothetical house with an imperial meter, with a hob, and a boiler (all appliances connected) a tightness test is done and a 5mb drop is found with no smell of gas. Situation is ID and supply is capped. If however the imperial meter was removed and a metric meter put in its place (I’m still in hypothetical house) which of the following would apply
1. The tightness test shows a drop of 5mb, no smell of gas and as such acceptable???? surely not.
2. The tightness test shows a drop of more than 8mb, Situation is ID and supply is capped.
3. Where a new meter is installed the installation is treated as new and as such no drop is allowed (this would apply to Julie Dee) but ruins my hypothetical house

Good Luck

Bob

 

[Gasguru]

Imagine we have a gas meter the size of a shed (this represents a unitary type domestic meter eg. U6 or G6). Also lets suppose we have another meter the size of tv (this represents our ultrasonic meters eg E6)

Pressurise each "meter" to 20mbar.

Now bang a hole in the side of each "meter".

We have exactly the same size hole and leak from each meter. However the pressure will drop more rapidly on our small tv sized meter (E6) due to it's smaller volume.

Our shed sized meter (U6) will fall at a much slower rate due to its higher volume.

Hence when we time our drop over 2 minutes we take account of the volume of gas within the meter and therefore allow twice the drop for the smaller volume meter.

In the second part of your question the answer is 2. Replacing the meter (with the smaller volume E6) will cause an increased drop and will therefore fail the T.T

 

[cowboyplumber]

Gasguru you really are . Fantastic explanation.

 

[bobs yer uncle]

Thank you Gas Guru, great explanation.

 

[chrishutt]

To answer the first part, it's to do with the different volumes of gas in each case and the compressibility of gas.

Let's say for the sake of argument that the volume of gas in a particular U6 meter installation is double the volume of the same installation with an E6 meter. In each case the gas pressure is initially at 20 mb.

The leakage of a certain small volume of gas will reduce the pressure of the remaining gas, but not to the same extent. If the leaking gas equals say 1% of the volume of the U6 installation, the same amount will equal 2% of the E6 installation.

Therefore the E6 installation is losing a greater percentage of its gas and will therefore suffer a greater loss of pressure, even though the amount of gas leaking is the same in each case. Does that make sense?

 

[mmalone]

I had my gas meter changed yesterday and was told that I have a minor gas leak, which is apparently "within limits". The gas man disconnected the meter anyway.

The problem is that I am about to rent the house out. Does having a minor leak that is within limits mean that I can still let it out? Or am I about to have to spend an absolute fortune having a corgi registered guy track down and repair the leak?

When the gas man disconnected the meter he said that as the leak was within limits it was "up to me what I did but he still had to disconnect it anyway". I should have thought to ask him at the time about this, I know.

I hope I've posted this in the right place.

Cheers,

personally wouldnt leave any leak myself even if within tolerences..

 

[ChrisR]

wouldnt leave any leak myself even if within tolerences

Never buy a digital manometer then! Using one which shows 0.01mbar, almost every installation I go to shows a drop!

Transco meter guys are not corgi registered

It's pétard, French for fart, controversy over whether it's a rope trap, or a small bomb

 

[kevplumb]

Transco meter guys are not corgi registered

that's cos they took the dog on chris

 

[Agile]

All I can say is that they should be registered!

Most routine meter changes are done by a contractor like Siemens, their staff are registered ( as operatives of Siemens ).

Tony

 

[Paul Barker]

Whenever I';ve called them to let bye they've been old Gas Board hands with loads of knowledge we usually spend a while chewing the fat. Must be in other areas they aren't experienced and better trained.

As regards the drop, I often find it necessary to remove the cooker beyonette socket and plug it before a pipework tightness test passes....