By: gaw On: Sun Mar 11, 2007 9:50 pm
On new masonry chimneys it is a round clay made of the same material as the square flue liner. My old house someone used a piece of 8" cast iron pipe!
My mother's house has had a coal fire going 24/7 for over 50 years and the chimney Flues were NEVER cleaned. Just use a shop vac and suck the fly ash out of the sump. Use a small mirror to look up the chimney for problems but burning anthracite coal only, you will likely never see any build up on the sides of the chimney.