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Thread: Orphaned gas water heater... what to do?

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  1. #1

    Default Orphaned gas water heater... what to do?

    Hi all,

    I just had a high efficiency gas furnace installed in my 1950s house and now my natural gas water heater is the only exhaust producer for my traditional flue tile chimney. I live in Maryland and my furnace installer said that while the current water heater is fine for now, when winter comes, I run a great risk of damaging my flue/chimney because the old furnace won't be there to heat up and drive moisture out. My current water heater is a 40 gallon unit and was installed in 1992 so it's time to get something new. I just don't know how to best spend the cash.

    I have a few questions that I would greatly appreciate your thoughts on.

    - I've been told that I need to move to a direct vent or power vent water heater or, if I stay with a traditional heater, install a very expensive flue liner ($500.00). Is this so? I hear the chimney flue opening will need to be elongated up the stack a few feet for the liner to enter the basement at a low angle avoiding a 90 degree bend. What a mess!

    - I'm getting numbers in the amount of $700.00 for installation of a traditional water heater (without the flue liner cost added), or $1500.00 for full installation of a power vent heater. Does this sound in the right range?

    - If I spend $1500 for purchase and installation of the power vent water heater, it really frustrates me that I'll need to spend another $1200-$1500 10 years from now to put in a new replacement water heater. Are there any 40 gallon long life water heaters out there that will allow me to get more for my money?

    - I was told that purchase and installation of a good quality tankless heater will cost close to $3000.00 given the need to upgrade my 3/4" gas line to something larger. A 3/4" line currently feeds my 95000 input BTU furnace and my 32,000 input BTU water heater. Do I really need to upgrade this line?

    - I have no basement floor drain and when the heater leaks, it really creates a mess. I hear there is hardware available to detect a leak and when this happens, a solenoid controlled valve shuts off the tank's water supply. Is there some sort of kit available for this or does my installer need to buy individual parts and piece it together?

    Thanks for reading and for any comments you can provide!


  2. #2
    In the Trades Bob NH's Avatar
    Join Date
    Oct 2005
    New Hampshire


    Your installer is trying to pressure you into buying something.

    What do you suppose happens to fireplace flues. I have two of them that are only rarely used, and they are in perfect condition after 41 years.

    Winter air is dry because it won't hold much water. You might get some superficial condensation in your flue when it is raining with 100% humidity outside, but it won't soak into fired flue tile.

    Replace your water heater when it needs to be replaced.

    You can get a water/leak detector for a few dollars, and have it operate an alarm. Water heaters don't usually rupture with great flows. They leak. If you are concerned, I would go with the detector and alarm.

    I suspect that a solenoid valve big enough for a water heater will be more than $100. They have systems for washing machines that might apply.

  3. #3
    DIY Member King3244's Avatar
    Join Date
    Dec 2004
    Kelowna, BC


    The smaller tankless water heaters are in the range of 175,000 to 200,000 btu and the larger ones go up from there so you might need a larger gas line, your installer should be able to figure that out and if he can't look for another installer.

    A Bosch 125 tankless uses a 5 inch b vent and will work great in an orphaned chimney the bigger model however needs to be direct vented so that could solve your chimney problem right there........just vent it through a wall to outside and close off your old chimney.

    Go to www.hvac-talk.com and then to residential hvac and search orphaned chimney for a wealth of information.

    I don't know that I agree with Bob NH and his take on orphaned chimneys but then I am not a journeyman plumber or hvac pro...........a little research might be in order.

    I went to a tankless water heater last October and I would never go back to the old way....although many will argue that point I am sure. But be sure to ask the nay sayers if they have one when they offer opinions.

    I hope I didn't open a can of worms here..........LOL!

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default nay sayer

    Why would a naysayer buy something he doesn't like, or believe in? As far as long life heaters are concerned, there are heaters with longer warranties, even lifetime, but the are the same heaters as the 6 year warranty ones. You just pay more for the insurance policy so they give you a new heater when the old one leaks.

  5. #5
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
    Join Date
    Nov 2005
    Central Florida


    You said "when the water heater leaks...". Does this mean it leaks now and then? If so, it's probably not a leak, but rather overflow from the pressure relief valve, which is a different problem altogether.

  6. #6
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    The problem is acids in the water vapor going up the chimney will condensate with the water vapor on the chimney flue walls and over time build up until they start doing damage to the brick. The flue size, chimney location, and time of year will affect the amount of condensation which will determine how fast the damage happens.

    A liner or power/direct vent heater are your only options.

    Even 80% furnaces require chimney liners because of this.

  7. #7
    I&C Engineer (mostly WWTP) Lakee911's Avatar
    Join Date
    Aug 2005
    Columbus, OH


    Quote Originally Posted by Bob NH
    What do you suppose happens to fireplace flues. I have two of them that are only rarely used, and they are in perfect condition after 41 years.
    Fireplace flues get warm enough by the fire and then they cool off when not in use. It's like Cass said, the acidic moisture from the combustion will condensate on the cold surface of the flue/chimney. When enough heat is produced, the moisture is completely carried out of the chimney. When left to condensate, it will damage the brick or even some flue liners as well--galvanized won't stand up to it.

    I had my chimnet lined when I had a new furnace installed last fall. They dropped in a large flex pipe from the top, capped it off with 'Martian Hat' and made some 90deg bends in the basement-all with the proper rise from the furnance and water heater to the flue.


  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Go to http://taco-hvac.com/uploads/FileLibrary/WagsBroc.pdf . You need to install a drain pan. It shuts both the water and gas off if it detects a leak.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9



    Thanks for the comments and information! Sounds like a traditional gas water heater with a flue liner is a good approach along with a leak detector. I was starting to lean toward a power vent heater but a friend said he had one and stated that it blows exhaust out of the house at a considerable rate.. greater than a laundry dryer. I called one of the heater manufacturers and they said that the blower on their 40 gallon model was rated at 1200 CFM. My clothes dryer kicks out air at about 200 CFM. While I know an open flue on a traditional heater has a fair amount of house air going up the pipe, this 1200 CFM sure seems like alot. I'll be drawing outside air through every crack into my old 50's house - could be chilly in the winter. If I go the power vent approach I think I'll need to consider a closed system.

    Thanks again.

    Mikey - The leak I'm talking about is my tightwad, procrastination, "I've waited too long to replace my heater and now the basement is wet" leak I really wish I had a floor drain nearby but it looks like the less expensive water detector many have mentioned or the system that jadnashua suggested may be a workable approach . Opening my wallet on a more regular basis would probably also help, but given the expense of these new systems, I'll probably stretch this next water heater as far as I can.

    jadnashua - thanks for the lead!

    Lakee911 - It's good to hear that you can put a 90 in the flue liner. This sounds like a much more agreeable solution than the one approach proposed to me. I'll have to get a flue expert to give me an assessment.

    King3244 - I'm not optimistic but I'll should look into the new gas line issue further to see if it is really necessary. If I can get by with the current line, the added cost for a 20 year heater may be worthwhile.

    Y'all have a good evening. - r/Tom

  10. #10
    Master Plumber master plumber mark's Avatar
    Join Date
    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
    Blog Entries

    Talking gas heaters

    I got a 75 gallon gas going into a normal tile chimmney

    it has about a 12 inch square tile going out the roof...

    Used to have a furnace tied into the same line......

    was told the same line of horsh shit,,,,,,,

    i maybe they are right, to get a flu liner to save the chimmney...

    but I am pretty sure the cmimmney will last
    another 50 years before I got to install that flu liner.

    so I am gonna wait.

  11. #11


    i have 2 water leak detector alarms.
    i bought them at a local harbor freight store for 10$ each.
    I tested them and they work good enough.

    unfortunetly i have polybutelyne piping.
    lucky for me they haven't gone off.


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