Our flue pipe is showing signs of going brown, is this normal?
The flue pipes will change colour depending on how hot they have been. Like all metals, when exposed to the heat they go through a process called tempering or metallurgy which is explained in more detail here.
If there are any oil deposits like fingerprints etc. on the pipes then these can show up once they have been heat cycled and are much harder to remove. Any time the flue is touched it is worth following our instructions and have them wiped down with some methylated spirits.
If there is a concentrated spot of heat like a ring around the pipe then this is an indication of a possible internal flue fire. If this is the case then a sweep would be recommended.