I take photos and video of the flues when I sweep, its the only way I can check the job. There is an inspection hatch that is too small to fit even a Victorian child labourers head so a camera is invaluable. There was no chimney at the end of the house this flue lives on, my lounge used to be a beast parlour, the flue is a nice German ADT on the outside wall and definitely not to UK building regs as it has an 85cm long tee, does it draw properly? Yes it does.
Creosote is your enemy and if you burn Pine or other conifers you will know your enemy well.
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