Even when you are burning right (wood, stove temps, glowing cat), you still encounter hurdles that you should not have. The Defiant's draft has been suffering. So, I pulled the pipe tonight to take a look. Massive amounts of build up. A few things: Wood is 2-3 years old. All Ash and Oak. I do not have a moisture meter, but, to put it in perspective, I have no problem getting the two cast iron stoves over 700 degrees and the 30 has hit 800 degrees. The chimney was cleaned at the start of the season. I do not have a Cat probe, but, the cat glows regularly so I know it is engaged. I have not been choking down the stove. I have been running it at a higher temp. So, I'll be cleaning the chimney tomorrow, and will seemingly need quite a large bucket to dump all the build up that I will be cleaning out. A cat probe will be installed this off season and at least one mid-season cleaning will take place next year to be sure the build up is being held in check.