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Direct exhaust water heater

Bill Kibbel

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The instructions for the vent terminals are always very clear for Canadian installations: 12" under any veranda, porch, deck or balcony.

For US installs it's always: "Maintain clearances in accordance with local installation codes and the requirements of the gas supplier".

Does anyone have anything to prohibit this:

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How many BTU? The following says if it's over 10,000 but under 50,000, it needs 12" clearance. Look under ©

National Fuel Gas Code NFPA 54/ANSI z223.1

Section 7.8 pages 54-52 & 54-53 THROUGH THE WALL VENT TERMINATION (a) A mechanical draft venting system shall terminate at least 3 feet above any forced air inlet located within 10 feet. Exception No 1 Provision does not apply to combustion air intake of a Direct Vent appliance. Exception No 2 This provision shall not apply to the seperation of the integral outdoor air inlet and flue discharge of listed outdoor appliances. (b) A mechanical draft system of other than direct vent shall terminate at least 4 feet below, 4 feet horizontally from 1 foot above any door, window, or gravity air inlet into any building. the bottom of the vent shall terminate at least 12 inches above grade. © The vent terminal of a direct vent appliance with an input of 10,000 BTU's or less shall be located at least 6 inches from any air opening into the building, and such an appliance with input over 10,000 BTU but not over 50,000 BTU shall have at least 12 inches vent termination clearance. The bottom of the vent terminal and air intake shall be 12 inches above grade. (d) Through the wall vents for Category II and Category IV appliances and noncategorized condensing appliances shall not terminate over public walkways or over an area where condensate could create a nuisance hazard or could be detrimental to the operation of regulators, relief valves, or other equipment. Where local experince indicates that condensate is a problem with Category I and Category III appliances this provision shall also apply. In addition to those rules follow manufactureres instructions.

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A colored smoke bomb would clearly demonstrate how wrong it is.

Tell me again why it's wrong. It's condensing so it's not really hot. It discharges outdoors where it's not trapped and where there's abundant fresh air to disperse it.


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I live in an area that is cold abt 11 1/2months a year. all direct vents are visible most of the time. the condensation on the wood is a real issue for us. it seems to keep the wood wet with a liquid that is slightly acidic and of course it forms hoary frost for several months of the year on surrounding surfaces.

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