Trust the professionals

[jon]

This is a snippet from a post of mine from last Tuesday:

Secondly she is having a new cooker and hob, changing from gas to electric, consequently I will need to cap the old gas feed as it's in the way.

I am a competent wet plumber but was wondering if there was any advice for a job like this (i.e. don't do it). It seems straight forward, Turn off gas at meter, cut pipe, make end good, then solder on new end cap, turn gas back on, and check for leaks with gas aerosol stuff. ( what about any gas left in the pipe when I'm soldering, will air have got into the system during the process, etc)

The general consensus was to get a Corgi registered person to do the job. Reluctantly I did this.

Now this work was taking place behind a washing machine, so access was sort of available. Anyway I always thought it was best practice to use soldered joint on gas, but it was acceptable to use compressions where there was access to the fitting. But if compression was used the yellow tape should be used. The Corgi plumber has used a compression with no tape, is this acceptable? Should I redo the job myself using a soldered joint, or should I just loosen the compression and wrap some yellow tape, or has he done an acceptable job?

TIA

Jon

[fred]

In article , jon writes

Compression joints do not require tape or any other sealant to make a good joint, this is true for both water and gas.

[Andy Wade]

Agreed - but what I'm wondering is this - when you create a dead-end in a gas pipe system like this, is there any requirement to purge it (to get rid of the trapped air) or do you just allow time and the natural diffusion of gases to do the job.

[Phil L]

There is no requirement to purge it and it would be pointless anyway as it's still connected to the main supply. There is a requirement to isolate a dead leg with water pipes because the water inside could stagnate and then find it's way back into the main.

[Phil L]

You should have just done it yourself, and no, there is no need for tape, gas isn't under much pressure anyway - you can stop it with one finger

[John Rumm]

IIRC there were two parts to the question, the first was with regard to a cast iron gas pipe that sounded like a disused feed? If so then dealing with *that* pipe would be better left to the gas suppliers.

Dealing with blanking a copper connection however is much simpler.

The gas (yellow) PTFE tape is for use on threaded connections that seal on the threads. A compression connection does not seal like this, and hence does not require tape.

(sometimes tape is used on the thread of a compression fitting as an aid to lubrication - it makes doing them up slightly easier but does not change their ability to seal.