Home>Discussions>TV>Ask This Old House>4" or 5" Venting for a Gas Boiler
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88 ways
4" or 5" Venting for a Gas Boiler
88 ways

I recently purchased a peerless MI-03 Boiler and discovered I could only fit a 4" chimney liner down my chimney. The Vent off of the boiler starts at 5". Is it safe to use the 4" chimney liner? I was able to use a 5" vent for 12" up off of the boiler to a 90 degree, 18" of 5" horizontally(small incline) and another 12" vertically before I connected to the 4" Chimney liner. My HVAC contractor said I would be okay. Any advice?

Thanks, Josh

I live in a two story row house

sabo4545
Re: 4" or 5" Venting for a Gas Boiler
sabo4545

Your best bet would be to call the manufacturer and check with them. They likely put a 5" opening on the boiler for a reason otherwise they would have used 4" if they could.

canuk
Re: 4" or 5" Venting for a Gas Boiler
canuk

The person that will be inspecting the boiler installation will have the definitive answer since they will sign off that everything is proper.

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