Can you vent a gAs fire Water heater out a perimeter wall

I recently inspected a split level home with a utility room that includes a 90% efficiency furnace and an electric water heater. The buyer wants to replace the electric water heater with gas. The question is does it have to vent through the roof. And if he vents it through a side wall what would be the considerations. Likely it would have to be some specific minimum distance from any penetrations, specifically doors and windows. Anyway this is beyond me and I am sure someone knows.The home is in an incorporated portion of Jefferson county west of Denver, CO.

Thank you for your response

There are direct vent and power vented systems that can be done horizontally. I'd imagine some water heaters could be retrofit with a new vent system but I'm not sure about that.

One thing to keep in mind with the power vent type is that if/when you lose power you also lose hot water. I haven't seen a lot of the direct vent type but an hvac contractor was just telling me about them last week. Maybe someone on here has some experience with them and will chime in.

No blow.....No Boil

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Originally Posted by Ted Menelly

No blow.....No Boil

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Not necessarily true. There are direct (horizontal) vent gas fired water heaters that use no electricity. Rheem makes one.

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Originally Posted by neal lewis

Not necessarily true. There are direct (horizontal) vent gas fired water heaters that use no electricity. Rheem makes one.

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Yep, there is that also but he was talking about the powered vents.

Not sure if I'm thinking of or using the terminology correctly but I'm thinking of the natural draft ones as direct vent and the electric fan ones as powered vent. I suppose the powered ones are a powered direct vent, if there is such a thing.

Direct vent means a balanced system that pipes in as much air as it needs by thermosyphon then exhausts, usually through a concentric vent.

You cannot use positive pressure on any vent not tested and listed for that application. That means Cat. I gas appliances cannot be power vented with an inline fan. You can use a wall termination power venter if that appliance is approved for use with one.

In the case with the WH, they make both power vented units that take air from the home and direct vent that bring in their own air and are thus decoupled from the home air.
HTH

Yes you can vent a gas fired water heater out of the wall if it is either a power vent unit. They do make two models of power vent units one is called a direct vent power vent, as Bob Harper pointed out it draws its combustion air from outside unlike a standard power vent unit which burns its combustion air from the dwelling.

Now lets say you do not want a power vent unit. Then their is the Atmospheric Direct Vent unit. It needs to be near an outside wall the hole for the wall must accommodate the thimble that passes through the wall. This unit has a 5" pipe coming off the top of the unit with a 3" pipe inside the 5" pipe. The larger pipe is the fresh air intake and the smaller pipe is the exhaust. These units are almost as costly as a power vent unit , but when the power does go out you will have hot water still.

Lots of people want to by a standard Atmospheric Vent water heater and vent them out the side wall. This is not allowed, every manufacture I dealt with wants them to be vented to roof or into a properly sized chimney system.

With the Atmospheric Direct Vent and the Power Vent options the installation manuals give you the clearances from doors, windows , and other items you must have proper clearance for. They also have a disclaimer to check with your local codes to ensure they do not have any additional requirements.

I hope this helps.