Section P3005 Drainage System
Changes in direction in drainage piping shall be made by the appropriate use of sanitary tees, wyes, sweeps, bends or by a combination of these drainage fittings in accordance with Table P3005.1. Change in direction by combination fittings, heel or side inlets or increasers shall be installed in accordance with Table P3005.1 and Sections P3005.1.1 through P3005.1.4, based on the pattern of flow created by the fitting.
FITTINGS FOR CHANGE IN DIRECTION
|TYPE OF FITTING PATTERN||CHANGE IN DIRECTION|
|Horizontal to verticalc||Vertical to horizontal||Horizontal to horizontal|
|Combination wye and eighth bend||X||X||X|
Double fittings such as double sanitary tees and tee-wyes or approved multiple connection fittings and back-to-back fixture arrangements that connect two or more branches at the same level shall be permitted as long as directly opposing connections are the same size and the discharge into directly opposing connections is from similar fixture types or fixture groups. Double sanitary tee patterns shall not receive the discharge of back-to-back water closets and fixtures or appliances with pumping action discharge.
Exception: Back-to-back water closet connections to double sanitary tee patterns shall be permitted where the horizontal developed length between the outlet of the water closet and the connection to the double sanitary tee is 18 inches (457 mm) or greater.
The size of the drainage piping shall not be reduced in the direction of the flow. The following shall not be considered a reduction in size in the direction of flow:
- A 4-inch by 3-inch (102 mm by 76 mm) water closet flange.
- A water closet bend fitting having a 4-inch (102 mm) inlet and a 3-inch (76 mm) outlet provided that the 4-inch leg of the fitting is upright and below, but not necessarily directly connected to, the water closet flange.
- An offset closet flange.
Horizontal drainage pipes in buildings shall have cleanouts located at intervals of not more than 100 feet (30 480 mm). Building drains shall have cleanouts located at intervals of not more than 100 feet (30 480 mm) except where manholes are used instead of cleanouts, the manholes shall be located at intervals of not more than 400 feet (122 m). The interval length shall be measured from the cleanout or manhole opening, along the developed length of the piping to the next drainage fitting providing access for cleaning, the end of the horizontal drain or the end of the building drain.
- A removable P-trap with slip- or ground-joint connections can serve as a cleanout for drain piping that is one size larger than the P-trap size.
- Cleanouts located on stacks can be one size smaller than the stack size.
- The size of cleanouts for cast-iron piping can be in accordance with the referenced standards for cast iron fittings as indicated in Table P3002.3.
Drain pipes shall be sized according to drainage fixture unit (d.f.u.) loads. The size of the drainage piping shall not be reduced in size in the direction of flow. The following general procedure is permitted to be used:
- Draw an isometric layout or riser diagram denoting fixtures on the layout.
- Assign d.f.u. values to each fixture group plus individual fixtures using Table P3004.1.
- Starting with the top floor or most remote fixtures, work downstream toward the building drain accumulating d.f.u. values for fixture groups plus individual fixtures for each branch. Where multiple bath groups are being added, use the reduced d.f.u. values in Table P3004.1, which take into account probability factors of simultaneous use.
- Size branches and stacks by equating the assigned d.f.u. values to pipe sizes shown in Table P3005.4.1.
- Determine the pipe diameter and slope of the building drain and building sewer based on the accumulated d.f.u. values, using Table P3005.4.2.
Branches and stacks shall be sized in accordance with Table P3005.4.1. Below grade drain pipes shall be not less than 11/2 inches (38 mm) in diameter. Drain stacks shall be not smaller than the largest horizontal branch connected.
|NOMINAL PIPE SIZE|
|ANY ONE VERTICAL|
STACK OR DRAIN
|DIAMETER OF PIPE|
|SLOPE PER FOOT|
|1/8 inch||1/4 inch||1/2 inch|
|11/2a, b||—||Note a||Note a|