Roger Mills wrote:

Try this:
[...]
Check with washing-up liquid that re-connected joint isn't leaking

The use of washing-up liquid for gas soundness testing is very strongly
deprecated since the salt content can lead to corrosion, eventually
causing leakage. A proprietary gas leak detection spray (available from
Screwfix) should be used.

For reference the full formal gas purging procedure can be found he
http://groups.google.co.uk/group/uk....e?dmode=source

--
Andy