Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Venting exterior tankless water heater placed over deck

I'm replacing a 40 gallon gas water heater to an exterior gas tankless water heater. It will go just outside of the current water heater location. This will be on the back of my house. I have a deck across the back of my house, so people will be around the install location.

Question: Do I need to vent the water heater through the roof? Or leave it ventless and let it vent under the eaves?


  • Jamie Hall
    Jamie Hall Member Posts: 23,318
    Check both the manufacturer's installation instructions and your local codes. They are probably pretty specific about how far the exhaust must be from a walkway or deck -- and I would be much surprised if you could exhaust it over the deck.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • fschaefer
    fschaefer Member Posts: 2
    Thanks Jamie. Finding City codes is ridiculously complicated. I've been looking all morning on the City of Austin website and find everything but venting codes. Guess I'll keep looking.
  • KC_Jones
    KC_Jones Member Posts: 5,739
    What brand and model is the tankless? As said there are typically venting requirements in the install manual that would be a good starting point.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Zman
    Zman Member Posts: 7,569
    Most local codes differ to manufactures instructions. I would start with the manual.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • PRR
    PRR Member Posts: 142
    > start with the manual.


    The manual has a page on venting. Here's one for hot-air, but hot-water is near the same fire and smoke, probably the same illustration but check the numbers for *your* burner.

    As I read it, you can blow smoke at your deck-dwellers. However pavement on public property they want 7 feet up. And only 12" from a soffit--- after watching my soggy exhaust over a couple winters I moved the stack to blow 3 feet out, so it would not come back against the soffit and soak the insulation.

    I can stand in the (propane!) exhaust plume but I'd rather not. In TX you use well-gas which may be stinkier than my distilled gas. Also the vent spits acid-water. Hasn't killed my weeds yet but could stain a deck.

    Pencil your idea and check. If this is a Permit/Inspection job, ask the official if there's any local rules beyond "manufacturer instructions". Or if s/he has seen a vent ON a deck and thinks it may be unwise.