I want to merge my 3" water heater vent and my 4" furnace vent together with a Y before exiting through the roof. What size pipe should the output side of the Y be? 5"???
Thank you,
Chuck
That works out to about the same cross sectional area. I don't know if there are any other things to worry about there or not.
Looks like there may be issues if either are powered. I read on one posting that if one was power assisted that it was not legal.
Bad idea, don't tie them together. The furnace will have a blower on it and can't legaly be tied to another vent. Most places no longer allow vents to be combined at all. Problem is the blower can force the fumes out of the draft diverter on the water heater back into the room.