Small Holes in Gas Furnace and Water Heater Exhaust Pipes

[LarryLeveen]

I was surprised to see a small hole in each of the exhaust pipes for the gas furnace and water heater in my new-to-me house. Is there any reason why there would be a hole in an exhaust pipe like this? I certainly have never heard of one.

They almost look intentional — or accidental but "regular". I don't want to sound like a crackpot, but could these be bullet or BB holes? Looks like there is another hole in the supply plenum on the left of the furnace exhaust in the first photo.

What is the proper way to patch these?

 

[Reach4]

They almost look intentional — or accidental but "regular". I don't want to sound like a crackpot, but could these be bullet or BB holes? Looks like there is another hole in the supply plenum on the left of the furnace exhaust in the first photo.

Could be gas analyzer sampling holes.

What is the proper way to patch these?

Furnace cement and/or screws.

 

[Sponsor]

 

[Fitter30]

Just go to a box store replace the fittings and pipe under $20. Analyzer holes 1/8" or 1 /4" pipe plugs might work.

 

[LarryLeveen]

Thanks. Glad to know there wasn't a shootout in the basement!