How to improve gas appliances chimney draft?

Home Maintenance Questions and AnswersCategory: House ChimneyHow to improve gas appliances chimney draft?
Question by JohnM

I have a question for you regarding the venting of my hot water boiler and hot water heater. First, a little background. I have a Weil-McLain boiler that is approx. 20 years old. 9 years ago we put in a flu liner after doing some work to the upper segment of the chimney and realizing that the mortar was in bad shape and that the venting should no longer be done just through the ceramic tiles inside the chimney. We just replaced that liner after having some leaking water issue last winter and when the a service tech came in for my regular pre-winter service this fall and found that the unit had basically no draft. So, the flue was replaced and the piping to the boiler and once the cold weather set in we started having a drip in the piping near the connection to boiler. I called back the company and they came out and, after assessing the situation, said I have a crack in my boiler and need it to be replaced. I have had two other companies in to look at the situation and both very quickly said it is not the boiler, it is a venting problem.

So, my question is: How can I maintain a warmer (hotter) environment in my chimney so that the gases don’t cool so fast and create the condensation that then falls back down into the pipe, causing leaking, etc..? I currently have a a 5 or 6″ new metal flu liner. Is there some double walled liner or some way of insulating that could keep this flu warmer and prevent what is happening? My chimney has 3 walls exposed to exterior cold (so it is a cold chimney) and the venting is traveling two stories… and estimated 30-35 ft to the top of the chimney.

Thanks for any advice/expertise you may be able to provide!


1 Answers
Dariusz Rudnicki Staff answered 1 year ago

Hi John,
1. One answer is on this page – . There is a YouTube video that shows liner insulating sleeve and its installation inside the chimney. Unfortunately, to complete this procedure existing liner would have to be removed, sleeve or blanket installed over the liner, tube and the entire assembly pushed back down the chimney.
You can also replace the existing liner (I’m assuming it is single wall) with a B-vent – double wall- pipe (it’s not going to work if you have corbelled – angled – section of the chimney), but if the existing one can be pulled up without being destroyed, it’s probably less expensive than a new pipe.
2. Second option is using chimney insulation mix. There a few available, this is just one of them –  I don’t know how much clearance you have between the existing liner and the clay tiles, but one of those methods should work for you. Let me know if this helped.

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