Switch from atmospheric to powered vent to reduce backdraft fumes?

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Emanresu2000

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I have a 13 year old 50g atmospheric vent water heater - it is located in a closet upstairs between two bedrooms. I has a 4" vent going straight up through the roof. Also, the house seems very airtight. Over the years we would smell combustion fumes upstairs occasionally, and it got a lot worse when I installed a new 150cfm capacity bathroom fan to vent a project area. I confirmed that we are getting a backdraft when this fan is on, or any two bathroom fans are on. A plumber looked at it and didnt see any installation issues, and the chimney top was just replaced last year when I got a new roof. So, I think the cause of the issue is just because of air pressure.

My hallway CO alarm has not gone off but the wife thinks the fumes are causing headaches and other health issues for the kids who's bedroom doors are adjacent to the water heater closet - and Im starting to believe it. Right now we try to keep a window cracked open but that is not a long term solution.

I was looking at options to replace it. I would prefer to stay with a tank heater. My question is whether switching to a power vent could reduce or avoid the backdraft issue?

My questions about this are:
1. would this really work, or is there better option?
2. can I exhaust into the existing 4" vertical metal chimney vent using a reducer?
3. will the fan be too noisy being directly next to two bedrooms?
 

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LLigetfa

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Do you have a makeup air vent for the furnace and/or a HRV? If not, consider it. If you have an HRV, it might not be balanced. Consider one that auto-balances.

Your direct vent ducting is likely not as air tight as it should be or the fumes are coming back in through a nearby roof vent. A forced air fan water heater could suffer the same issue. Also, they can be very noisy.
 

Emanresu2000

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I do not have an HRV but I dont think its related to the furnaces - they are not in the interior of the house and the fumes are worse in the summer and when using the exhaust fans. Im not familiar with HRVs so I dont know if they would help with that. Im pretty confident that the fumes are from a backdraft - using a smoke test I could see air was coming down and out the water heater vent when our exhaust fans are on.
 

Fitter30

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Theres two type of units design for pressuring a house hrv heat recovery ventilator or evr energy recovery ventilator. Hrv will pass humidity erv won't. These units are for indoor air quality. Ever have a blower door test? Tells how tight house is. Some utility companies offer them with a energy audit. A too tight house needs fresh air for indoor air quality. Power vent heater will only make the house worse. Water heater in closet read tag for btu input also measure closet door and louvers openings. Try blocking the door open a 1" .
Direct vent heater brings air in and vents in a concentric fitting.
 
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John Gayewski

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You need makeup air. Simply running a properly sized duct into that room from the outdoors would likley fix the issue. The only issue would be if you want that air to go through a heat exchanger to match the indoor temp. and recover some of the heated or cooled air from in the house. Personally I'd just duct in a vent from outside since this is in a closet. The erv just brings in outdoor air when you exhaust air from inside your house. So running the fans would not create negative pressure there by sucking exhaust from your water heater.
 

Emanresu2000

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OK thanks all! I will look into HVR/ERV systems.

Sounds like a powered vent water heater is a bad idea. What about a direct vent water heater?
 
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