Interpretation No. 4067 – Clean-Out Spacing and Access in Drainage Systems

Manual Reference Section: 4
Applicable Code: BC Plumbing Code (1998), Part 7, Section 7.4
Status: Approved by LMPCC / VIPCC
Revision Note: This interpretation was revised (No. 4067-2) to address additional considerations not covered in the original ruling.

Background

The Plumbing Officials’ Association of British Columbia first issued Interpretation No. 4067 to address questions about the required placement and spacing of clean-outs in building drainage systems. The original ruling (183 words) dealt with the fundamental requirements. Following continued enquiries from inspectors who encountered installation conditions falling outside the scope of the initial text, the Association published a revised version (No. 4067-2, 292 words) that expanded the guidance to cover direction changes, concealed piping, and the relationship between clean-out access and finished construction.

Subject Matter

The original enquiry asked at what intervals clean-outs were required along horizontal drainage piping and whether an additional clean-out was necessary at each change of direction. The revision addressed supplementary questions about clean-out accessibility once wall, ceiling, or floor finishes had been installed, and whether clean-out plugs located above grade had to be brought to the surface of the finished floor or wall.

Ruling

The Association determined that clean-outs shall be installed at intervals not exceeding those prescribed in the applicable subsection of Section 7.4 of the Code. For horizontal drainage piping, the maximum spacing between clean-outs was established at 15 metres. An additional clean-out was required at each aggregate change of direction exceeding 135 degrees (measured as the sum of all fittings in a single run between two clean-outs).

At the base of each vertical stack connecting to a horizontal building drain, a clean-out was required to permit rodding in the direction of flow. Where a building drain exited the structure, a clean-out at or near the foundation wall was also mandated.

Revised Provisions (No. 4067-2)

The revised interpretation added the following clarifications. Where drainage piping was concealed within a wall, ceiling, or floor assembly, the clean-out had to remain accessible through a cover plate or access panel of sufficient size to permit removal of the clean-out plug and insertion of clearing equipment. Painting over, plastering across, or otherwise permanently concealing a clean-out fitting was not acceptable.

Clean-out plugs installed in horizontal piping below a finished floor were required to be extended to the floor surface using an approved riser or extension fitting. This provision applied equally to slab-on-grade construction and to suspended floor assemblies.

The revision also referenced prior rulings from the Building Code Appeal Board (BCAB) in which appeals had been upheld where clean-outs were rendered inaccessible during finishing work, reinforcing the expectation that accessibility must be maintained throughout the life of the installation.

Scope of Application

This interpretation, as revised, applied to sanitary and storm drainage systems in new construction and to significant alterations where existing drainage piping was extended or rerouted. It did not modify requirements for underground building sewers beyond the property line, which fell under municipal sewer bylaws.