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Venting 95% gas furnace and hot water heater thru common PVC pipe

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Hi Dariusz,

I am going to replace my 30 year old gas furnace with a new 95% gas furnace. I am assuming I have to replace my hot water heater with a one that will be venting thru a PVC pipe as well. I am planning to vent these 2 appliances thru one pipe installed inside of my existing chimney. What are the requirements when connecting these 2 PVC pipes in my basement before entering the chimney space ?

It is a condominium situation and I don't have too many choices to vent the new furnace. It would be very difficult to vent thru the side wall, I would have to go thru the finished portion of my basement.

Thank you much,

Waldemar
asked in Heating System by waldek (120 points)
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1 Answer

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Hi Waldek,
 
Unfortunately you cannot vent your furnace and water heater using just one PVC vent pipe. Each one of those appliances requires its own vent. Even assuming that your water heater will be a high efficiency / condensing type, just like your furnace, their common venting is not permitted.
 
If the chimney is 100% yours, there are no other appliances discharging into it, you may be able to run two PVC pipes inside the flue. However, there might be issues with termination of the pipes and fitting both of them (or even 3 if there are combustion air restrictions inside the condo unit) into the chimney flue.
You probably need an experienced HVAC contractor to evaluate your situation.
 
One other option would be using an electric water heater instead of a gas fueled unit. Just remember that if your building has a common chimney (used by more than just your appliances), a PVC vent pipe cannot be inserted into it.
 
Click “comment” below if you have more questions.
answered by darekrudy (21,730 points)
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