Drain and Vent

Drain and Vent / Full bathroom

Tub, toilet and sink, sink on the opposite wall: air admittance valves, wood floor

The tub and the toilet share one wall; the sink sits on the wall across the room, so its drain crosses the floor. Each fixture is vented with an air admittance valve instead of a pipe to the roof, with the main stack still open to the air. Some cities do not allow AAVs: check before you buy. The floor is wood framing over a crawlspace, basement or room below: the drains run between or through the joists.

Where the fixtures are
All on one wallSink across the roomTub drain at the far wall
Tub or shower
TubShower
Sinks
One sinkDouble vanity
How it is vented
Wet ventSeparate ventsAAVs
Floor
Wood floorConcrete slab

Get this room's rough-in sheet, $7

BathtubToiletBathroom sink
Your room as a display drawing. The pipe sizes, the vents, the falls and every rough-in height are on the sheet.

What is on your rough-in sheet

Three Letter pages for this room (bathtub, toilet, bathroom sink), drawn for a wood floor. Print them and tape them to a stud.

  1. Sheet 1

    The riser drawing

    Every drain and vent pipe drawn at its size, the vents dashed, the fall marked on every run, and where each fixture ties in.

  2. Sheet 2

    Plan and wall

    The floor plan with every drain located from the walls, and the plumbing wall with every stub-out, valve and shower head height.

  3. Sheet 3

    The counter list and the checks

    Every fitting by name and size, counted, to read out at the supply house. Each trap arm checked against its limit, and the test the inspector will ask for.

Checked before it is drawn

  • Every branch sized for the fixture units it carries (IRC Table P3005.4.1)
  • Every trap within its distance to a vent (Table P3105.1)
  • Wet vents sized and ordered as P3108 requires
  • Every fixture vented; AAVs placed as P3114 requires
  • Falls of 1/4 or 1/8 in per foot by pipe size (P3005.3)

Before you cut

  1. Pull the permit. Most places need one for new drains and vents, and the inspector sees the rough-in before the walls close.
  2. Find your code. This sheet follows the IRC. Many western states use the UPC, and some cities ban AAVs. A call to the building department settles it.
  3. Shut the water off before you cut into a supply line, and open a faucet below to drain it.
  4. Check the joists. On a wood floor, a drain across the joists means bored holes, and holes have size limits.

For this room

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