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Section P-1105 Ventilation of Branch or Horizontal Pipes
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Every branch, horizontal soil pipe, or waste pipe to which a group of two or more fixtures is to be connected shall have a vent of the same size as the branch by: extending the branch full size as required in Section P-1103.4; connecting to the stack vent 6 inches above the highest fixture; or connecting to the vent stack 6 inches above the highest fixture connected to the branch. The horizontal branch from the base of a stack shall be connected to the house drain as prescribed in Section P-904.4. Table P-904.4 is not subject to these requirements.
Where the center of a water closet outlet is not more than 48 inches in developed length from the center of 4-inch vented soil pipe on a vertical line, or through a wye or wye and 1/8 bend on a vented horizontal line, connection of small fixture wastes - not exceeding two that are 1-1/2 inches or less in diameter - to the side of an ideal bend (closet bend) above the center line without an additional vent, or by using no-hub, copper, ABS or PVC pipe and fittings in accordance with Section P-902.0, shall be approved by the Department. Where the center of a water closet outlet is not more than 18 inches from the center of a 3-inch vented soil pipe and the 4- inch ideal bend (closet bend) is connected directly to a sanitary tee on a vertical line, connection of small fixture wastes - not exceeding two that are 1-1/2 inches or less in diameter — to the sides of the bend above the center line without an additional vent and in accordance with Section P-904.5 shall be approved. As an alternative to increasing the size of a stack from 3 inches to 4 inches, a merion fitting shall be used to receive the discharge of a water closet and small fixture wastes.
The water closet soil line connected to a merion fitting shall be a maximum of 8 feet developed length. The ideal bend (closet bend) shall not be less than 4 inches nominal diameter when receiving the discharge of small fixture wastes. When using 3-inch ideal bends (closet bend) to receive discharges of water closets, this fitting shall be a blind bend containing no drainage connections for other fixtures.
On existing stacks in buildings where the center of a water closet outlet is more than 4 feet but not more than 8 feet from the center of a vented soil pipe, an additional 1-1/2 inch vent will be permitted if the vent is not longer than 30 feet, provided the conditions are the same as in Section P-1105.1.1.
Any single water closet or pedestal urinal branch more than 8 feet in length or any single waste branch for fixtures other than water closets or pedestal urinals more than 12 feet in length shall have a vent sized at least one-half the diameter of the branch pipe. Depending on its length, the number of fixture units connected shall be in accordance with Table P-1110.4.
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