DWV Fundamentals

1
DWV Fundamentals

• Plumbing Systems
• CNST 305
• Environmental Systems 1
• Dr. Berryman

2
Trap

• Uses water seal to prevent backflow of gasses
  into building

3
Venting

• Removes dangerous odors and explosive gasses
• Prevents
• Positive pressure
• Negative pressure

If not properly vented, a waste slug could either
blow out or siphon the trap seal
4
Venting (cont.)

• Drainage systems flow by gravity
• As such EVERY TRAP or PLUMBING FIXTURE MUST
  HAVE A VENT

5
Isometric Diagrams
6
Combining Vents
7
Example Isometric Diagram
8
Design Guidelines for Drain and Waste (for most
codes)

• All traps must be vented
• The waste stack cannot be smaller the the largest
  horizontal branch connecting to the stack
• 4 branch cannot connect to a 3 stack
• At least one waste stack same as building drain
• No branch pipe smaller than the one that proceeds
  it
• Above ground cannot be less that 1¼
• Below ground cannot be less than 2

9
Design Guidelines for Drain and Waste (cont.)

• 1 ¼ drain pipe can handle on 1 DFU
• A drain line cannot be smaller than the trap arm
  to which it is connected
• Use 4 trap arm for floor mounted water closets
• Some codes do allow 3 (however, this is not
  generally recommended)

10
Design Guidelines for Vents (for most codes)

• Above ground venting cannot be less than 1 ¼
• 1 ¼ vent can handle on 1 DFU
• Underground venting cannot be less than 2 in
  diameter
• Vents must be a certain distance from the trap
  that it serves
• (tble 19 ANSI A40
• 1993 Standard)

11
Design Guidelines for Vents (cont.)

• An individual vent must not be less than ½ the
  size of the drain that it connects
• 4 drain cannot connect to any pipe less than 2
  in diameter
• An individual vent should not be larger than the
  drain that it connects
• Downstream piping always bigger than the upstream
  section
• Downstream, in its natural state, is going OUT of
  the building

12
Design Guidelines for Vents (cont.)

• A vent line must be 6 above flood level rim of
  the fixture before turning horizontal
• Branch vents must slope toward a drain
• Some codes require that at least one of the
  buildings VTR be 4 in diameter or larger

13
Next Time

• Sizing DWV