18-29-916.3 Developed length.

   The developed length of individual, branch, circuit and relief vents shall be measured from the farthest point of vent connection to the drainage system to the point of connection to the vent stack, stack vent or termination outside of the building.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

18-29-916.4 Multiple branch vents.

   Where multiple branch vents are connected to a common branch vent, the common branch vent shall be sized in accordance with this section based on the size of the common horizontal drainage branch that is or would be required to serve the total drainage fixture unit load being vented.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

18-29-916.4.1 Reserved.

Editor's note – Coun. J. 10-14-21, p. 37722, Art. IX, § 7, repealed § 18-29-916.4.1, which pertained to multiple branch vents exceeding 40 feet.

18-29-916.5 Sump vents.

   Sump vent sizes shall be determined in accordance with Sections 18-29-916.5.1 and 18-29-916.5.2.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

18-29-916.5.1 Sewage pumps and sewage ejectors other than pneumatic.

   Drainage piping below sewer level shall be vented in the same manner as that of a gravity system. Building sump vent sizes for sumps with sewage pumps or sewage ejectors, other than pneumatic, shall be determined in accordance with Table 18-29-916.5.1.

Table 18-29-916.5.1
Size and Length of Sump Vents

Discharge Capacity of Pump (gpm)	Maximum Developed Length of Vent (feet) a
	Diameter of vent (inches)
	1 1/4	1 1/2	2	2 1/2	3	4
10	No limit b	No limit	No limit	No limit	No limit	No limit
20	270	No limit	No limit	No limit	No limit	No limit
40	72	160	No limit	No limit	No limit	No limit
60	31	75	270	No limit	No limit	No limit
80	16	41	150	380	No limit	No limit
100	10 c	25	97	250	No limit	No limit
150	NP	10 c	44	110	370	No limit
200	NP	NP	20	60	210	No limit
250	NP	NP	10	36	132	No limit
300	NP	NP	10 c	22	88	380
400	NP	NP	NP	10 c	44	210
500	NP	NP	NP	NP	24	130

 

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 gallon per minute = 3.785 L/m.

NP = Not permitted.

a.   Developed length plus an appropriate allowance for entrance losses and friction due to fittings, changes in direction and diameter. Allowances shall be obtained from NBS Monograph 31 or other engineered sources. An allowance of 50 percent of the developed length shall be assumed if a more precise value is not available.

b.   Actual values greater than 500 feet.

c.   Less than 10 feet.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

18-29-916.5.2 Pneumatic sewage ejectors.

   The air pressure relief pipe from a pneumatic sewage ejector shall be connected to an independent vent stack terminating as required for vent extensions through the roof. The relief pipe shall be sized to relieve air pressure inside the ejector to atmospheric pressure but shall be not less than 1 1/2 inches (38 mm) in size.

(Amend Coun. J. 10-14-21, p. 37722, Art. IX, § 7)

18-29-917 Vents Not Required .