The following fittings shown and discussed below are some of the most common fittings you would use to construct any DVW (drainage waste and vent) system. They may be made of different materials, such as: copper, ABS, PVC or cast iron and have different joining methods, however their shape will be roughly the same.
In drainage, sanitary tee's (usually just called a tee) are always installed as the picture shows it, with the curved part of the tee connecting a horizontal pipe to a vertical pipe. In venting, a tee may be installed on the horizontal to connect a vertical vent.
Wye's are used to connect both horizontal to horizontal, and horizontal to vertical pipes. Often used in combination with a 45 degree fitting.
90 Degree Elbow
Not to be used at the bottom of a vertical drainage pipe on sizes smaller than 4".
45 Degree Elbow
Are commonly used in a DWV system to gradually change direction of flow, such as at the base of a stack. They are also often used in combination with a wye.
22.5 Degree Elbow
Not commonly used, but may help create difficult offsets.
Used to connect two sections of pipe.
Used at each plumbing fixture to prevent sewer gasses from escaping, by keeping a water seal in the trap.
Used to connect the fixture outlet pipe (tail piece) to the trap.
Same as a wye but typically used to connect back to back fixtures.
Double Sanitary Tee
Can only be used on the vertical, and will require a clean-out above the flood level rim of the fixtures connected to it.
Used to reduce upstream pipe size. May also be used for venting to increase the size of the upper portion of a Vent.
Same as a reducer, but fits inside the hub of another fitting.
Plugs are commonly installed as an access port (clean out) at various points in a DWV system.
Used to keep an air tight seal on an unused pipe end.
Used on below grade drainage pipes to protect from sewer back-ups. To learn more see: Backwater valves.
Must be installed to allow cleaning of the drainage system. To learn more see: clean outs
Used as a means to mount a toilet/water closet. See installing a water closet.