- The developed length of the fixture drain from the trap weir to the vent fitting for self-siphoning fixtures, such as water closets, shall not be limited.
- A trap arm serving only a bathtub, tub/shower combination, or shower may be increased to 9 feet with a slope of not less than 1/8 inch per foot.
|SIZE OF TRAP (inches)||SLOPE (inch per foot)||DISTANCE FROM TRAP (feet)|
1 inch per foot = 83.3 mm/m.
|DISCHARGE CAPACITY OF PUMP|
|MAXIMUM DEVELOPED LENGTH OF VENT (feet)a|
|Diameter of vent (inches)|
|10||No limitb||No limit||No limit||No limit||No limit|
|20||270||No limit||No limit||No limit||No limit|
|40||72||160||No limit||No limit||No limit|
|60||31||75||270||No limit||No limit|
- Developed length plus an appropriate allowance for entrance losses and friction caused by fittings, changes in direction and diameter. Suggested allowances shall be obtained from NBS Monograph 31 or other approved sources. An allowance of 50 percent of the developed length shall be assumed if a more precise value is not available.
- Actual values greater than 500 feet.