Clearance between direct vent intake and DWV vent?

[Dougster]

Is there a minimum lateral separation on a roof between a combustion intake air vent and a DWV stack vent? I am also concerned about the exhaust from a cooking stove which also terminates nearby.

According to Inspectapedia there are "critical concerns with combustion air contamination for heating appliances". However I can't find the codes that cover these contamination sources.

This is for a condensing tankless water heater with direct vent intake and exhaust pipes (either two separate pipes, or concentric configuration) to be terminated above a sloped roof.

 

[Killer95Stang]

My condensing tankless uses one of these going up through my roof. Exhaust flows straight out through the center and intake air is taken in from around the mushroom lip. With warmer air being pushed out of the exhaust tube under pressure, I don't think you would have an issue with this kind of setup.\

Also, the instructions that came with my Rheem unit wanted at least 18" away from any windows or openings, when exhaust was taken horizontally out of the side of a building. Having at least that amount away from another exhaust source is probably sufficient. Where is your unit going to be mounted? Since mine is mounted in a water heater closet that only has access from outside and is sealed from the house, I guess it doesn't really apply to me.

 

[Sponsor]

 

[Dougster]

Killer95Stang

I follow your reasoning but am not sure the building department or a flow engineer would agree since my question is combustion air intake contamination from an uncoupled exhaust source.