You Don't.... To comply with the law ..... Get an approved engineer (needs not to be British gas)The reason is you may kill yourself or others sometimes these jobs are not as simple as they seem... Sorry Good luck
chris(ex gas engineer 30 years)
November 2008
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.