Tankless WH's flue vent height?

Are there different requirements for the flue height? They had the furnace flue heights right. I have not seen these plastic kind before. This is new construction.


New one on me also.
Is that rubber or plastic flashing?

Plastic. first i have seen of it. i see alot of rubber though.

Looks almost like concentric but also has the 18 inch minimum between intake /exhaust assuming that is them.

It’s a listed direct venting appliance, probably condensing type. The answer will only be found in the manufacturer’s installation instructions. It probably has a zero clearance requirement too.

Looks OK to me. Pay attention to the condensate drains, not that it will produce much in our subtropical climate, but they still have to be configured properly and trapped (look for a loop).

Are you referring to the AC condensate drains? I am not familiar with WH condensate drains.

Nope. High efficiency water heaters (all of those with plastic vents AFIK) are condensing type. The flue gasses cool enough that in cool weather water will condense out of it. These need special vents of plastic or stainless (because the condensate is corrosive) and condensate traps with drains. Most of these vents are concentric with exhaust in the center and intake in the outer. They typically require no clearance to combustibles. In the Houston area, you will usually see the condensate drain tie into the pan drain downstream of the pan.

Here in Rinnai type which looks like what you have http://www.rinnai.us/documentation/downloads/Ubbink_Condensing_Vent_manual.pdf