wellygary:

 

mattwnz:

 

I do wonder if they have replaced wrong bottle, or if both bottles could have only been half full. I can't tell which bottle they replaced either. 

 

 

A full bottle is close to 80kg, an empty one is just over 30, its unlikely they took the wrong one, 

 

Get a jug of hot water and pour it down one side of the bottle, then feel down the wet path with you hand, when you hit cold that's the gas level  

 

Thanks, I will try that. Will an empty bottle have any gas in it all, and where is the line on a full bottle, or is it right at the top.