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Chimney Lining Advice

Bob Harper
Bob Harper Member Posts: 1,028
Sorry for the double post--flying fingers I guess. Yes, Z-Flex has responded with a 316 alloy but it still is inferior to most other liners I see. For one, their rollforming technique still allows some liners to come apart into a spiral. Their AL29-4C for CAT. III & IV is improved.

I see a lot of rigid with very rough joints that effectively cause more friction loss than corrugated. That and each joint is a question mark with regards to CO and water vapor leakage. Size the liner to the appliance. Flex requires a 20% derating. If it won't fit, you can either bust out flue tile or change the appliance to one that can vent into that chimney. Since most heaters are oversized, I routinely recommend homeowners consider option B if their equipment is old. I've walked away from a few because the installer put a monster into a flue that has no chance of venting even if the flue tiles are removed and a 8" round smooth walled liner installed. Sometimes, just switching the water heater to a power vented one, tankless or indirect tank will remove enough BTUs from the stack to make it work. Really peeves me to see brand new tall boy water heaters into already overloaded flues. See it all the time. Rarely have I seen the contractor come back and make it right. Usually the homeowner eats it or they leave it as is without the liner and take their chances. It is pretty rare to find a case where the calculations were actually run for the sizing.
Bob

Comments

  • Jim Erhardt_3
    Jim Erhardt_3 Member Posts: 80
    Chimney Liners

    I need to line an exterior masonry chimney that is used for an oil-fired Buderus. I'm getting more and more condensation resulting in rotted flue pipe and the time has come to fix this problem. Combustion specs look fine and the boiler is being fired at about 90% of its rating.

    The chimney is exterior (west side, 3 sides exposed) and roughly 16 feet tall with easy access to the top from the roof. According to Buderus, I need a 5-inch liner and the interior dimensions of the flue tile is 7 inches.

    What kit would you recommend? I'm thinking straight lengths of stainless steel pipe screwed together as I drop it down from the top, though I'm not sure what I will need to do at the bottom to make the 90-degree turn in to basement.

    Any advice/recommendations on the easiest way to do this would be appreciated!
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    Z flex

    stainless corrugated. I use the kit with the ss T on the bottom for a little capacity/drop rather than just bending the pipe out into the mech room. The snout may have to be extended out of the chimney base if you are deep. Prepare to cut a 9" wide by about 16" high slot in the existing chimney base to slip the T/liner assy in.
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981
    My call ,

    I would forget the kit,and most definitely forget about screwing stainless pipe together....and find a pro to do it.

    I'm not knocking your ability or anyones to fit a liner. A professional does it right. This isn't a place to be "guessing I'm doing it right".

    There are many costly objects at "chance" here. A chimney and a boiler are pretty important and expensive items to waste on a "guess". JMHO. Chris
  • Bob Harper
    Bob Harper Member Posts: 1,028


    Thx J.C.A.; I do Not recommend Z-Flex liners. I find them all the time rotted out. What I recommend is as JCA said but specify a type 316Ti alloy liner installed to the listing. The codes now require liners to be listed, so that precludes any homemade stainless rigid pipe. Pros used stainless flex but use a brand with a transferrable lifetime warranty. Forget the tee: pull it through like a hockey stick for improved flow. Sizing important but so is the configuration of the chimney connector. Buderus do not like flues that are oversized, undersized or cold, high mass masonry. Properly size listed flex liner is the way to go.
    HTH,
    Bob
  • Bob Harper
    Bob Harper Member Posts: 1,028


    Thx J.C.A.; I do Not recommend Z-Flex liners. I find them all the time rotted out. What I recommend is as JCA said but specify a type 316Ti alloy liner installed to the listing. The codes now require liners to be listed, so that precludes any homemade stainless rigid pipe. Pros used stainless flex but use a brand with a transferrable lifetime warranty. Forget the tee: pull it through like a hockey stick for improved flow. Sizing important but so is the configuration of the chimney connector. Buderus do not like flues that are oversized, undersized or cold, high mass masonry. Properly size listed flex liner is the way to go.
    HTH,
    Bob
  • Ken D.
    Ken D. Member Posts: 836
    Chimney

    I do prefer stainless steel rigid sections, but it would depend on the length of the chimney. Up to two floors, rigid pipe is great. Overthat, installing gets hairy. That is when I would use the flexible. If the chimney size is marginal, the flexible will exacerbate the problem as the flex is not perfectly straight all the way down and could affect draft.
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    just so

    there is no misunderstanding, the Z flex I'm referring to is 316 SS and is UL listed. part # is 20ILKTX.

    I prefer the T for some wiggle room/dump if the homeowner (or the oil co.) misses an annual cleaning. These things happen :)
This discussion has been closed.