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Power vent water heater is backfeeding cold air

Hi guys, We here in Michigan just got over a single digit 11 day cold spell. This is where you really can test your basement for cold air leaks. Speaking of that, I waked by my water tank and was pretty much blown back by a wave of cold air. So when the fan kicks on it pulls air from the basement to vent the gas out the rim joist through 2" pvc tube. Ok, that's great. Now when the fan is not blowing the pvc is just letting the cold outside air to backfeed right through the fan intake into the basement. I guess it would need a spring loaded flapper or something on the end of that pipe outside to block it off when fan is not running. Sadly I cant find any application for this. Any ideas, thanks

IMG_20180110_175659805[699].jpg1.75 MB
Asked by Mid michigan
Posted Jan 10, 2018 8:24 PM ET
Edited Jan 11, 2018 6:22 AM ET


2 Answers

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Mid Michigan,
Either your house is depressurized (due to the operation of bathroom exhaust fans, the range hood fan, or the clothes dryer), or you have big leaks in your top-floor ceiling (the attic floor).

If you seal the attic leaks, you will reduce the stack effect (and reduce the entry of cold air into your basement). Here is a link to an article that describes the necessary work: Air Sealing an Attic.

Concerning exhaust fans, there's not much you can do about the bath fans and the clothes dryer -- but if you have a big range hood fan, you should read this article: Makeup Air for Range Hoods.

Answered by Martin Holladay
Posted Jan 11, 2018 5:52 AM ET


2 X 4 pvc coupling....4" dryer vent outside.....done

Answered by tom may
Posted Jan 13, 2018 12:37 PM ET

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