Permissible drop and TT

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Permissible drop and TT

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kirkgas

Just to start a wee debate cause the telly is crap, this came up in college and caused a few comments,the scenario is: existing system existing appliances U6 meter, 22mm pipe, 2mb drop over 2 mins, no smell, no issues etc
The question is "MUST YOU ISOLATE THE APPLIANCES TO CONFIRM IF THE LEAK IS ON THE APPLIANCES AND NOT THE CARCASS SO YOU CAN LEAVE IT"
I want your opinion on what you must do, NOT on what you think is better, eg some say its better to isolate the appliances to confirm its not on the pipes,
My interpretation from IGE/UP/1B is
new install with or without appliances or existing install with no appliances then no drop allowed, or if the installation is existing with existing appliances and the drop is less than the table max permissible drop then the installation passes the test, therefore no further action required
Discuss
 
I was taught, that as everything is existing and it's within the permissible tolerances then no further action is required
 
I agree with that interpretation but you've got to be careful if replacing an appliance because you need to prove that the drop is on another appliance so that when you carry out the test when you finish work you know what the drop is on the old pipework and appliances. Aguy working for the same firm as me got RIDDORed for leaving a leak after a job. He tested detected a permissible drop, changed the boiler and tested again. The drop was the same so he assumed it was safe. Customer smelt gas over the weekend and called Transco out who found a leak on the meter unions where he'd removed it to solder, The drop had been on the old boiler and the leak on the meter unions was coincidentally the same as the dop on the old boiler.
 
I got taught that you must isolate as there is NO permissible drop on pipe work. How do you know whether it is on pipework or appliance unless you isolate the appliances?
 
once you isolate the appliances and prove the pipe work is leaking youve made yourself a problem! if the appliances are on it and it drops within limits and no smell , no problem, but its your choice then if you want to leave a leak. I hate leaks and normally hunt them down, hobs are main problem, meter compression joints becoming an issue and poor solders are common as well
 
no permissible drop on the carcass,if isolating appliances still shows a drop ID,personally lame i dont care if it makes me a problem it means i have found something that could blow up a house and take life
 
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therules give you some leeway and there are minor drops that can be impossible to find. My favourite leak was with an ex BG engineer who laid gas mains for years, he installed his own cooker and i was called in 22 years later after transco had cut him off. I could smell the leak in the hall and he pointer to the cooker which I got behind to find an unsoldered elbow. His comment was, it isnt worth the bothor boy, you have seen a leak till you seen a cracked main ****ing gas:), and the firemen hiding behind their red toy
 
My answer to that question would be that you can't leave it at all because it's not less than the maximum permissable drop. To be able to leave it, it would have to be less than 2mbar.
 
What is an existing appliance and what is a new appliance is what I struggled with..... Worcester bosch fitted 6 months ago, can you have a permissible drop on this? what about if it is fitted 2 years ago?
 
Keefy said:
My answer to that question would be that you can't leave it at all because it's not less than the maximum permissable drop. To be able to leave it, it would have to be less than 2mbar.
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WHAT?????????
Where are you taking this info from? Haha you are just confusing what would appear to be an already confusing scenario.
REMEMBER everyone, I want to know your interpretation of the law, as in what you MUST do, I've no interest in what you do because you want to work above the law as you interpret it
 
if its been there a week and you turn up its existing if you bolt it on its new and if you have not put anything on the pipework yet its pipework, not rocket science after all the rules are there for simple folk like us to use
 
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jase158 said:
I got taught that you must isolate as there is NO permissible drop on pipe work. How do you know whether it is on pipework or appliance unless you isolate the appliances?
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Have a read at the TT document if you have it,
For those that have access to it its on the bottom of p18, if I remember tomorrow I will quote the paragraphs I'm on about to see what we think then
 
kirkgas said:
Have a read at the TT document if you have it,
For those that have access to it its on the bottom of p18, if I remember tomorrow I will quote the paragraphs I'm on about to see what we think then
Click to expand...

I haven't got it, but seem to remember it saying something like, to do a tightness test you must do the whole installation, then test the pipework only. under the procedure for tightness testing? might be wrong
 
jase158 said:
What is an existing appliance and what is a new appliance is what I struggled with..... Worcester bosch fitted 6 months ago, can you have a permissible drop on this? what about if it is fitted 2 years ago?
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This is easy, if its not yet commissioned its new, once its commissioned and I revisit its existing
Taking this to extremes if you fit a boiler today you can't have a leak, if I visit tomorrow and test I can have 4/8 leak as its existing, BUT although it can be left I would argue against leaving this one as the spirit of the reg is to allow for microscopic leaks which appear due to we're and tear and loss of grease etc in the fittings, where on a new boiler do you even have grease now, so if a leak has appeared since yesterday its dodgy leaving it,
 
jase158 said:
I haven't got it, but seem to remember it saying something like, to do a tightness test you must do the whole installation, then test the pipework only. under the procedure for tightness testing? might be wrong
Click to expand...

No might about it haha
 
I've always understood it that if it's within the maximum acceptable drop with existing pipework and fittings you can leave it because the leak is so minute it would never reach it's explosive gas to air ratio due to other factors like ordinary room air changes. That's not to say I'd be comfortable leaving say, a 3 or 3 and a half mbar drop though, even though the law would allow me to.
 
Keefy said:
I've always understood it that if it's within the maximum acceptable drop with existing pipework and fittings you can leave it because the leak is so minute it would never reach it's explosive gas to air ratio due to other factors like ordinary room air changes. That's not to say I'd be comfortable leaving say, a 3 or 3 and a half mbar drop though, even though the law would allow me to.
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I have met a few installers that think this but you are not allowed any drop on any pipework new or old.
 
Done my resit in jan asked the trainer that exact question as it seems different people have different views. I was always taught any drop you must confirm carcase is sound by isolating app and he said this was correct. I have had a 2 mb drop on a llords which had been passed for years and after some investigating I found a unsoldered but fluxed 15mm elbow behind kitchen carcase.amazing how well flux will hold and over a long period!
 
leethegasman said:
I have met a few installers that think this but you are not allowed any drop on any pipework new or old.
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both of you are right but people need to read the complete posts and not extract bits of them or this will go on forever.
 
the book says you can leave a situation like this, but maybe the books wrong :disappointed:

a 2mb drop at 20mb would also show a drop on a 10mb let buy test.
if there's no drop at 10mb, you could be looking at a let buy on the ecv, with a gas leak equal to the let buy

so imo, only leave this situation if there's a drop on the 10mb let buy test as well :smile:
 
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