Frequently Asked Questions (FAQ)

For additional room to my existing residential house:

What sewer/drain pipe size do I use for Toilet drain & vent? for bath tub drain & vent? for bathroom wash basin drain & vent?

What pipe material should I use? ABS,PVC or metal?

Can I run sewer/drain pipe through exterior/interior footing (footing is 24 inches deep)?

What maximum distance from toilet other fixtures (bath tub, wash basin or sink) must the vent be placed?

What is the minimum grade/slope required for the sewer/drain line (for back flow prevention)?

Table 7-5 of the 2002 County of Los Angeles Plumbing Code requires that the minimum drainage pipe size for a water closet is 3 and the minimum vent shall be 2 pipe size. A bath tub drain shall be a minimum of 2(horizontal) or 1 ½ (vertical) drain pipe size, with a minimum 1 1/2 vent pipe size. A lavatory requires a 1 ¼ minimum drain and vent pipe size. The minimum slope required for drainage piping less than 4 in pipe size is ¼ per foot slope.

Section 701 .1 of the plumbing code lists all of the approved drainage piping materials. Schedule 40 ABS or schedule 40 PVC are limited to not more than two stories of residential construction. A drainage pipe cannot be imbedded in concrete or masonry, but may be installed when not subject to undue strain or stresses. Typically, wrapping or sleeves will provide adequate protection when penetrating concrete. The building sewer must be a minimum of two feet from the building, and the edge of a trench (deeper than the footing parallel to the building sewer) must be 45 degrees away to avoid imposing a load on the pipe.

Vents must be installed within the required trap arm distance per Table 10-1 of the plumbing code. You may review the plumbing code over the counter at the La Puente District Office.

County of Los Angeles Department of Public Works
Building and Safety Division
La Puente District Office
16005 East Central Avenue
La Puente, CA
(626) 961-9611

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