How to stop rain from getting down a Chimney.

So, to prevent rain from entering the chimney, we simply install a rain cap and flashing and storm collar to protect the roof area where the flue penetrates.
For non-solid fuel such as gas, then a rain cap is required. , so there are plenty of options, including open terminals with mesh, recommended by British Gas for condensing boiler applications.
 
For example, terminating chimney in a traditional stack lined with Triplelock our Uniterm Type A is designed to fit on to a chimney without a pot, while Type B is designed to be installed directly to the top of an existing round chimney pot.
 
For solid fuel the best termination is an open termination, unfortunately with the UK weather we have to look at protecting the chimney.
 
However, despite best efforts and technology, some rain will always get down, but minimising the amount with innovative designs means that the chimney and flue system will last a long time without any deterioration.
 
If you choose a HETAS Approved Installer, then they will use their expertise to install the chimney system to maximise it’s lifespan according to all rules and regulations.

Also, with all chimney systems, you should have a HETAS Approved chimney sweep regularly maintain the chimney at least once a year – ideally between the Spring / Summer months.