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  1. #1
    Join Date
    Oct 2014
    Location
    Maryland, DC, and Northern Virginia, electrical only
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    444

    Default Gas water heater vent grandfathered without metal?

    A replacement gas hot water heater in a cellar (in Maryland, in a Washington Suburban Sanitary Commission inspected area) has galvanized vent duct that goes into an old chimney, ceramic-lined. Plumber commented that these are now really supposed to be retrofitted with metal liners, and WSSC might not pass the installation. Any comments?

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  2. #2
    Join Date
    Mar 2007
    Location
    Near Philly, Pa.
    Posts
    1,682

    Default Re: Gas water heater vent grandfathered without metal?

    Any chimney must be suitable for the class of service. I inspect chimneys professionally and have never found one lined with terra cotta that did not warranty relining with a listed liner. For one, there is no such thing as a code compliant chimney. They just aren't found in the wild.
    FYI, a gas water heater is the most dangerous appliance in the home. Ones vented into unlined masonry flues are even more hazardous. Just plan on calling for a liner on any heater flue that has not already been relined. Note that many relined flues are downsized and some are not completely relined. Since NFPA 211 calls for a level II upon sale or transfer of real estate, you should recommend them on every chimney.

    Keep the fire in the fireplace.

  3. #3
    Join Date
    Oct 2014
    Location
    Maryland, DC, and Northern Virginia, electrical only
    Posts
    444

    Default Re: Gas water heater vent grandfathered without metal?

    Quote Originally Posted by Bob Harper View Post
    FYI, a gas water heater is the most dangerous appliance in the home. Ones vented into unlined masonry flues are even more hazardous..
    Thanks for your information, Bob. Is it a CO hazard, fire, or both? (No CO alarms activated with the previous gas-fired water heater in the house, FWIW.)


  4. #4
    Join Date
    Mar 2018
    Location
    IL
    Posts
    7

    Default Re: Gas water heater vent grandfathered without metal?

    Quote Originally Posted by Bob Harper View Post
    Any chimney must be suitable for the class of service. I inspect chimneys professionally and have never found one lined with terra cotta that did not warranty relining with a listed liner. For one, there is no such thing as a code compliant chimney. They just aren't found in the wild.
    FYI, a gas water heater is the most dangerous appliance in the home. Ones vented into unlined masonry flues are even more hazardous. Just plan on calling for a liner on any heater flue that has not already been relined. Note that many relined flues are downsized and some are not completely relined. Since NFPA 211 calls for a level II upon sale or transfer of real estate, you should recommend them on every chimney.
    What Bob has said is very true. I am a certified chimney professional and gas water heaters need to be appropriately lined. Clay flue tiles are almost always in need of being replaced. If there are any cracks in the tile, any gaps between the tiles, protruding mortar joints, and other failures, the system fails inspection.

    I moved from the northeast, where most heating was oil and wood, to the St Louis area about 2 years ago. This area is almost all gas and this issue is a HUGE problem. We find completely collapsed flue systems where water heaters and furnaces vent into them all the time. I've had a handful of customers have symptoms of carbon monoxide poisoning. There are multiple issues that can come from water heaters not being properly lined. Of course you have the carbon monoxide issue. The gases can leak out of the system and into the home. You also have condensation problems. The stack temperatures don't stay hot enough and the gas starts turning into liquid. We get calls all of the time about "roof leaks near the chimney" when it is in fact an improperly lined gas system pumping water into the home and ruining their home. A stainless steel liner solves this issue. Especially an insulated stainless steel liner (which is what I almost always use). You also get breakdown of the masonry inside the chimney. I see this all of the time. Many times I get calls about a customer needing tuckpointing because of water damage and I come to find out that most of the water damage is coming from inside the chimney because of a wood, oil or gas system pumping into a chimney without proper lining. What also happens is the interior brick deteriorates over a long period of time and then falls down into the chimney and plugs the thimble where the appliance goes into the chimney. Super bad. I see this a LOT!

    I hope this helps.


  5. #5
    Join Date
    Sep 2013
    Location
    Oklahoma
    Posts
    2

    Default Re: Gas water heater vent grandfathered without metal?

    Nobody on this thread has mentioned the fact of getting the appliance to draft correctly. Need to check the mechanical code for the specifics. That is real problem. A residential 80 % efficient gas water heater does not have enough heat to warm a masonry cheminy to draft. Neither does a high efficiency furnace.


  6. #6
    Join Date
    Mar 2018
    Location
    IL
    Posts
    7

    Default Re: Gas water heater vent grandfathered without metal?

    Quote Originally Posted by Phillip Condreay View Post
    Nobody on this thread has mentioned the fact of getting the appliance to draft correctly. Need to check the mechanical code for the specifics. That is real problem. A residential 80 % efficient gas water heater does not have enough heat to warm a masonry cheminy to draft. Neither does a high efficiency furnace.
    I did mention condensation, stack temperatures, and insulating liners. But yes, if the stack temperatures are not hot enough then the chimney may not draft properly. Your statement about 80% efficiency not drafting is often true but not always true. An internal chimney is insulated by the home itself and can sometimes technically still draft just fine. Especially in a tall stack. But I'm still going to re-line it. I actually saw a water heater going into a very tall external masonry chimney last month that was drafting very well. I still relined it.

    I almost always insulate the liner no matter the situation. The liner manufacturers recommend it, most appliance manufacturers recommend it, it creates better clearance to combustibles, hotter stack temps (better performance, longer life), etc. If I see a water heater or furnace going into a clay flue system I am recommending it be lined with insulated stainless no matter what. For my reasons listed above and because of draft.


  7. #7
    Join Date
    Sep 2017
    Location
    WV
    Posts
    34

    Default Re: Gas water heater vent grandfathered without metal?

    Quote Originally Posted by david shapiro View Post
    A replacement gas hot water heater in a cellar (in Maryland, in a Washington Suburban Sanitary Commission inspected area) has galvanized vent duct that goes into an old chimney, ceramic-lined. Plumber commented that these are now really supposed to be retrofitted with metal liners, and WSSC might not pass the installation. Any comments?
    You will find this under the orphaned appliance code in the WSSC code book, in the past many gas furnaces and gas water heaters were connected into a terracotta lined chimney and they worked fine Several years ago with the advent of 90 plus furnaces with direct vents to the outside an engineer came up with the orphaned appliance idea and inserted it into code with the idea that a water heater by itself would not develop enough heat in the chimney to draw. Great idea but what about all the years the water heater exhausted into the chimney in spring summer or fall when the furnace wasn't running? I today still have not received an answer from WSSC except that it is in our code and you need to fix it.


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