Drain Pipes and Vent Stacks

Drain pipes and vent stack sizing.

Vents transports sewer gas through the building to open air space. Properly installed the vents prevents traps siphoning and sewage gas to leak into the interior building.

Different codes in different jurisdictions exists and must be adhered to locally. In general we talk about

individual vents
relief vents
circuit vents
branch vents
stack vents

Individual vents

Individual vents serve individual fixtures.

Sewage vent - individual

This vents only one fixture but may connect into an other vent that extends to open air.

an individual vent should be at least one-half the size of the drain it vents (no less than 1 1/4", 32 mm)

Relief vents

Relief vents provide additional air to the drainage system where the primary vent is too far from the fixture.

Sewage vent - relief

an relief vent should be at least one-half the size of the drain it vents (no less than 1 1/4", 32 mm)

Circuit vents

Circuit vents are used with more than one fixtures. A circuit vent is installed before the last fixture extend up to open air or connects to an other vent that extend to the outside

Sewage vent - circuit

an circuit vent should be at least one-half the size of the drain it vents (no less than 1 1/4", 32 mm)

Branch vents

Branch vents are vents extending horizontally that connects multiple vents together.

Sewage vent - branch

Stack vents

A vent stack is used only for the purpose of venting.

Sewage vent - soil stack

Vents are normally sized by using the "Developed Length" (total linear footage of pipe making up the vent) method.

Maximum length of vent stacks and relief vents

Maximum length of vent stacks and relief vents
Size of Soil Waste Stack (in)	Length
	Fixture Units Connected	Diameter of Required Vent Stack (in)
	Fixture Units Connected	1 1/4	1 1/2	2	2 1/2	3	4	5
1 1/4	2	30
1 1/2	8	50	150
1 1/2	10	30	100
2	12	30	75	200
2	20	26	50	150
2 1/2	42		30	100	300
3	10		30	100	200	600
	30			60	200	500
	60			50	80	400
4	100			35	100	260	1000
	200			30	90	250	900
	500			20	70	180	700
5	200				35	80	350	1000
	500				30	70	300	900
	1100				20	50	200	700

Drainage and Vent Pipes

Materials used in drainage an vent pipes according US standards.

Materials used in drainage an vent pipes according US standards
Piping Material	US Standards
Acrylonitrile butadiene styrene (ABS) plastic pipe in IPS diameters, including Schedule 40, DR 22 (PS 200) and DR 24 (PS 140); with a solid, cellular core or composite wall	ASTM D2661; ASTM F628;ASTM F1488; CSA B181.1
Cast-iron pipe	ASTM A74; ASTM A888; CISPI 301
Copper or copper-alloy pipe	ASTM B42; ASTM B43; ASTM B302
Copper or copper-alloy tubing (Type K, L, M or DWV)	ASTM B75; ASTM B88;ASTM B251; ASTM B306
Galvanized steel pipe	ASTM A53
Glass pipe	ASTM C1053
Polyolefin pipe	ASTM F1412; CSA B181.3
Polyvinyl chloride (PVC) plastic pipe in IPS diameters, inclu-ing Schedule 40, DR 22 (PS 200), and DR 24 (PS 140); with a solid, cellular core or composite wall	ASTM D2665; ASTM F891; ASTM F1488; CSA B181.2
Polyvinyl chloride (PVC) plastic pipe with a 3.25-inchO.D. and a solid, cellularcore or composite wall	ASTM D2949, ASTM F1488
Polyvinylidene fluoride (PVDF) plastic pipe	ASTM F1673; CSA B181.3
Stainless steel drainage systems, Types 304 and 316L	ASME A112.3.1

Drain Pipes and Vent Stacks