Common venting of Furnace & Water heater

This thing worked…but I know it’s not right! Thoughts?

What exactly do you see wrong with it. Having the pic turned the right way would help.

The water heater should vent above the furnace vent, back drafting can occur in its current set up. It should be further evaluated and corrected by a licensed/qualified person…

Right side Up

I would say its not an issue due to the fact at such an extreme vertical pitch for both there is no chance for backdraft. Yes typically the smaller venting appliance goes on top but due to their positioning here vertically, it s almost same as a ‘Y’. If no signs of backdrafting is seen , i would not call it out. The top also gets larger n diameter which is good and will prevent backdrafting IMO

I was following Derek’s line of thinking. I also however see some logic to Christopher’s theory. There was no evidence of backdrafting either with the furnace on or off while the water heater was fired.

Looks like I have one vote to correct, and one vote to not call it out…

Shucks I thought that was a horizontal install I was going to say it can not properly vent with the flue traveling down:shock::mrgreen:

I have never seen a tapered tee like that for sale at my local HVAC supplier. They use those for high velocity dust collecting systems, and they are usually custom built. That tee does not appear to be double wall so it should have 6 inches clearance from ceiling, besides the water heater vent needing to go above the furnace vent.
It also looks like the installer is using a plug end at the furnace for a 4 to five inch transition. If he were to check the manufacturers recommended installation it would probably suggest that the connector vent should be 4 inch all the way to the B vent.
Finally maybe its the light, but the facing 90 degree elbow going back looks like its aluminum, in which case it should be 22 ga or more, but is probably dryer vent.

It’s a reducing wye, not a tee, very common at my wholesale house.
Not sure about the 6" to combustibles rule because I can’t tell how far it is in the picture but the sheetrock ceiling would never be a problem with this configuration in my opinion. Not sure why the flue increaser fitting on the furnace but both flues will work great and not backdraft.


Prefer to see each vent terminate into the vent on a 45 degree with a lower cleanout.

Have seen problems where condensation within the line of either vent causes water dropout extinguishing the burner and/or causing damage to the water heater.

I can’t tell from the pic, but it looks like the furnace vent starts out at 6", then reduced to 4". I think the Y should be turned around, which would make the water heater vent above the furnace vent.