The video isn't clear re weighing gas bottles to assess how much is left. What I had meant to say was: weigh the full bottle when buying a new one and this will be about 9.7kg. Then deduct 3.9kg for the 7.8 litres of gas which gives the tare weight of the bottle which should also be printed on the tag on the collar. I record this on a post-it note on the locker wall then weigh the bottle using luggage scales, deduct the bottle weight and the difference is how much gas is left. 1kg propane = 2 litres.
