garage heater

[jpa6969]

can I use 4" flexible aluminum vent pipe for part of exhaust for a garage heater, I already have the hard pipe outside through wall thimble

 

[Showkey]

NO.........absolutely no.........really really bad idea.

Assuming the “standard power vent garage heater” sold at the big box store:
horizontal venting CAT III is the minimum
Vertical class B is the minimum

Find and read install manual.........it very specific what venting materials are required.

 

[jpa6969]

Thanks

 

[jpa6969]

can I use galzanized fittings to make up the difference

 

[Buckgnarly]

can I use galzanized fittings to make up the difference

Not if propane and horizontal, it can make for acidic condensation. My buddy used galv single wall to vent my radiant tube for about 75 bucks, and within 2 Winters it rusted through. I got Cat 3 this Fall and did it right, though it cost 300. My buddy is cheap, I'm not.

 

[jpa6969]

its natural gas

 

[Buckgnarly]

its natural gas

Looking at the combustion of nat gas and propane, they both produce water and carbon dioxide....which can combine to make carbonic acid.
If horizontal I'd still do Cat 3. My problem was the carbonic acid collected at a joint and rusted through

 

[pbon]

can I use galzanized fittings to make up the difference

Not allowed under code for horizontal. But if no inspector will see it you can do what you want. It used to be allowed and seemed to last a long time.