Sizing DWV

Plumbing Systems

CNST 305 Environmental Systems 1Dr. Berryman

4bc Drain, Waste, Vent Chapter 2,5,6 Appendix C (Wentz) and  8.3 - 8.5 (Toa)   

Design GuidelinesDRAIN/WASTE All traps must be vented The waste stack cannot be smaller

the the largest horizontal branch connecting to the 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” 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

VENTS 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 An individual vent must not be

less than ½ the size of the drain that it connects

An individual vent should not be larger than the drain that it connects

Downstream piping always bigger than the upstream section

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 building’s VTR be 4” in diameter or larger

Sizing Drain Waste Determine number of plumbing fixtures to

install Layout fixtures in space to codes (ie ADA) Determine site utilities Generate isometric Determine minimum trap size for each

fixture (tbl 2-2) Determine DFU Add DFU values starting from the farthest

end of system

Drain/Waste Iso

90o

60o

30o

TDL

Determine DFU…From Tbl 2-2

GIVEN:

•Water Closet – Siphon jet w/ flushometer valve, pressure = 15 psi

•Wall Urinal – Siphon jet with ¾” spud/flushometer

•Lavatory

•TDL = 100’

Determine Trap Size for Drains

From Table 2-2:

•Water Closet = 3”

•Wall Urinal = 2”

•Lavatory = 1 ¼”

Add DFU

•Water Closet = 6 DFU

•Wall Urinal = 4 DFU

•Lavatory = 1 DFU

Size Waste Branches

Sizing Waste (cont.)

Sizing Vents

Complete DWV Isometric

Sizing Circuit or Loop Vents

Next Time Test Review In class homework assignment

• Review notes and reading• Able to use books/notes• Due 10 minutes before end of class• We will grade and review assignment

Next week – Start HVAC

GIVEN:

•Water Closet – Siphon jet w/ flushometer valve, pressure = 15 psi

•Wall Urinal – Siphon jet with ¾” spud/flushometer

•Lavatory

•TDL = 100’