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  1. #1
    Join Date
    Apr 2011
    Posts
    14

    Keep Using Chimney?

    I recently had my gas forced hot air heating furnace replaced. I used to have an 80% furnace that vented through a chimney. It has been replaced with a 97% furnace that is sealed combustion and vents through the basement wall with PVC pipe. My gas domestic hot water heater hasn't been changed. It still vents through that chimney. The contractor who installed the furnace never mentioned it, but someone else said that having only the water heater vent through that chimney raises issues: specifically that there's now maybe not enough hot exhaust gases going up chimney so the chimney could be damaged/corroded, etc. over time. But even in the past there was at least six months a year where the furnace was off and only the water heater was using the chimney so if that was OK what's the problem now? If it's really a problem, the solution would seem to be to change out the water heater to a direct vent model and no longer use that chimney. That's an expense I'd rather not incur if unnecessary. Current water heater (Rheem 50-gallon) is over 12 years old, but works just fine. Never any problems. I drain it once a year to remove sediment -- just enough so that water runs clear, a few inches into a small bucket.

    What do folks think I should do?

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,900
    Yes, an orphaned water heater should have an appropriately sized liner kit installed in the chimney.

  3. #3
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,976
    Do a search for the term "orphaned water heater".
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #4
    Join Date
    Apr 2011
    Posts
    14
    I see. But still curious about why it was OK in the past to have at least six months a year where the furnace was off and only the water heater was using the chimney. Any thoughts?

  5. #5
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,831
    Quote Originally Posted by dnfuss View Post
    I see. But still curious about why it was OK in the past to have at least six months a year where the furnace was off and only the water heater was using the chimney. Any thoughts?
    Because it's hot out when heater is off and the chimney stayed warmer. In the winter those bricks can get cold...
    Give a man a fish, he will eat for a day. Teach a man to fish, he will eat for a lifetime.

    Give a man a capacitor, doesn't know what to do. Teach a man to install it, now he knows everything.

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,900

  7. #7
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    When the water heater is vented alone the flue gases / product of combustion which also contains carbonic acid enters a clay tile it may reach its due point temp. and condence in the chimney which wil be the demise of your brick and motor / clay tile.
    Even if you had another 80% unit installed the chimney is to be lined to size it for the amount of btu's that will be vented through it

  8. #8
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,706
    what type of chimney is it?
    B-vent metal chimney or masonary? chimney on outside wall or up middle of house?

  9. #9
    Join Date
    Sep 2011
    Posts
    50
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 12-21-2012 at 07:13 PM. Reason: non AOP member

  10. #10
    Join Date
    Apr 2011
    Posts
    14
    Quote Originally Posted by t527ed View Post
    what type of chimney is it?
    B-vent metal chimney or masonary? chimney on outside wall or up middle of house?
    It is a masonry chimney in the middle of the house.

  11. #11
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,706
    as long as it's not over sized and has terracotta liner it would pass around here.

    best thing to do would be getting a chimney guy to look at it.

    worst case you have a liner pulled down, sized for water heater.

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