I believe you re still allowed to use a combination drain vent which means oversizing the drain 2 pipe sizes.
Do floor drains require a vent.
As water goes down a drain air is needed to equalize the pressure in the drain line.
If the outlet of the trap were down at the same level as the sanitary main and the piping was installed such that there was a wet vent or circuit vent then the trap would be vented.
It can be done but takes some creativity.
The true vent is aligned vertically and attaches to your drain line through the roof.
What is a plumbing vent.
Today houses are vented through the roof.
Vents are a major component in a home s drainage system.
Just as drain pipes remove water and waste from your home the plumbing vent pipe also known as a plumbing air vent removes gas and odors it also allows fresh air into the plumbing system to help water flow smoothly through the drain pipes however no water.
Roof flashing made from heavy grade rubber lead or sheet metal holds the vent pipe in place.
Drain pipes take the wastewater to the soil stack.
If the drain lines in your home have poor venting as in figure a for example water rushing down the drains will pull water from nearby p traps.
If the drain is within 5 feet of a wall the pipe can be run towards the wall and a vent run up the wall.
The horizontal vent pipe runs right next to the closet.
Venting allows water to pass out of the drains easily.
Through the stack sewer gases are carried up to the roof through vent lines.
True vents also have no water running through them.
If the toilet drain does not connect directly to a vent you must find another way to vent it.
This is the purpose of a venting system.
All the faucets and water appliances in a house use this same system of drains pipes and vents.
This is best implemented if a fixture rests close to the stack and the top floor of your home allowing the stack to serve as a vent.
The plumbing vent also known as a vent stack helps regulate the air pressure in your plumbing system.
Toilet vent option 1.
The same holds true for plumbing vent pipe.
If the drain line runs away from the wall where you want the vent use a reducing y and a 45 degree street elbow to point the vent line toward the wall.