Can I put a put a double 90 upside down in a vent installation.
In other words have the vent coming down and sweeping 90 degrees in two different directions.
Thanks

can I put a put a double 90 upside down in a vent installation.
In other words have the the vent coming down and sweeping 90 degrees in two different directions.
Thanks

If you are asking if you can vent downwards, absolutely not! You cannot even vent laterally with an even grade! It must be on a grade .slope upwards from the heating appliance to the chimney connection at no less than 1/4" per foot of horizontal run


Flue vent connectors for "B" or "L" Vents: A vent connector connects gas equipment to a flue or chimney. Appliances having draft hoods and installed in an attic or concealed space must use Type B or L connectors. Appliances installed in basements can use Type B or Type L or metal pipe (.0304" thick) or aluminum pipe (.012" thick). Gas fired equipment should not be connected to any flue serving solid fuel appliances.

Multiple gas vents into a single flue: Where two or more vent connectors enter a common gas vent, chimney flue or single wall metal pipe, the smaller connector shall enter at the highest level consistent with available headroom and clearance to combustibles. Avoid unnecessary bends and secure all joints with sheet metal screws or other approved means.

Metal flue vent connectors should also be joined with the female (wider) ends facing "up" so that condensate and creosote that may form inside of the flue connector remain inside of the flue pipe. Our photo (above right) shows that foil tape was used to join two flue vent connector pipes of different diameters from a gas fired heating appliance . Foil tape is not a suitable substitute for the necessary adapter to join the two different diameter flue vent connectors.
Horizontal vent length limits: The horizontal length of a vent connector to a natural draft chimney or vent serving a single draft hood appliance shall not be more that 75% of the height of the vertical portion of the chimney above the connector. [NFPA 1992 (7.10.10)].

The maximum horizontal length of vent connectors per the GAMA tables is limited to 1.5 feet per inch of diameter with a provision of a 10% reduction in capacity for each multiple of the length permitted. The venting tables must be consulted to size an adequate venting system.

Watch out: allowable flue vent connector length calculation can be a bit more complex than that rule of thumb,
Slope upwards from the heating appliance to the chimney connection at no less than 1/4" per foot of horizontal run
Be kept as short as possible - long runs get cool, produce condensate, soot and debris and rust and clogging
Have flue pipe sections joined by three screws (two screw joints easily separate to vent dangerous flue gases into the building.

I'm sorry, I was not very clear in my question. I am talking about a bathroom plumbing vent. I have a vent coming down from my attic I would like to split it off in two directions in the joists above my bathroom. The space is limited above the ceiling and with the slope I need. Assuming everything else is to code, can I use this fitting upside down?

P327-020 - Spears P327-020 - 2" PVC 90° Double Elbow (http://www.pexsupply.com/Spears-P327-020-2-PVC-90-Double-Elbow)



Sorry for the confusion.

Hi Mike

That fitting wouldn't work in my area... reduces 2 - 2" elbows into 1 - 2" fitting.

I think you will be better to use a sanitary tee fitting with a street 90 in one end.

Good luck!

Mark

Hi Mark,
So excuse my ignorance, but wouldn't the Sani Tee be doing the same thing?
What I have is 2 - 2" vents running up through my bathroom wall, one from the basement bath and laundry and one from the bathroom lav, and tub. I also have another 2" vent running up from the bathroom shower and toilet to the attic into the 3" vent. I had wanted to bring that 3" vent down into the ceiling above the bathroom and split it off into the 2 - 2" vents. However I found that there was not enough room for the 3x2 sanitee.
What if I use the same fitting showed above, but as a 3" and then put two 3x2" bushings in it?
Thanks Mark

Or can I put a bushing on the 3" vent coming down and then use a 2" sanitary tee with a street 90? That would fit. The sanitary tee would be upside down in this installation correct?
Thanks again

There is no need to continue the vent from the basement up past the first floor... can connect into the first floor vent. Here, connect the vent from the basement group at 48" to center off the finish floor into the first floor vent... sanitary tee fitting is upside down.

That should eliminate the need for the double 90... yes? If not, simply put the fitting is illegal and the sanitary tee fitting and street 90 aren't. You decide.