Andy Munyon
SAWHORSE
Yes, based on the California Plumbing Code (CPC), you can use an all-abs drain, waste, and vent (DWV) system in a mixed-occupancy building.
The key is that the HCD limitation is based on the number of residential stories, not the total height of the building.
The Code Rule Explained
The California Department of Housing and Community Development (HCD) amendment states:
"[HCD 1 & HCD 2] abs and pvc installations are limited to not more than two stories of areas of residential accommodation."
Let's break down how this applies to a three or more-story building:
Count the Stories of Residential Accommodation: Your building has two floors of residential use.
Compare to the Limit: The code permits installations in buildings with "not more than two stories" of residential use.
Conclusion: Since your building has exactly two residential stories, it meets the requirement. The non-residential ground floor does not count toward this specific limitation.
Because the residential portion of the building complies with the two-story limit, the entire building's DWV system, including the piping serving the non-residential ground floor, is permitted to be constructed from abs.
Important Installation Requirements
Even though abs is permitted in this scenario, remember that its installation must still comply with all other code requirements, the most critical of which in a multi-story building is fire safety:
Firestopping: Every penetration of a fire-resistance-rated assembly (like the floor-ceiling assemblies between each story and any rated walls) must be protected with an approved firestop system. This is mandatory to maintain the fire separation between floors and occupancies.
In summary, a three-story building can be fully piped with abs for its DWV system because the number of residential stories does not exceed the two-story limit
set by the HCD.
The key is that the HCD limitation is based on the number of residential stories, not the total height of the building.
The Code Rule Explained
The California Department of Housing and Community Development (HCD) amendment states:
"[HCD 1 & HCD 2] abs and pvc installations are limited to not more than two stories of areas of residential accommodation."
Let's break down how this applies to a three or more-story building:
Count the Stories of Residential Accommodation: Your building has two floors of residential use.
Compare to the Limit: The code permits installations in buildings with "not more than two stories" of residential use.
Conclusion: Since your building has exactly two residential stories, it meets the requirement. The non-residential ground floor does not count toward this specific limitation.
Because the residential portion of the building complies with the two-story limit, the entire building's DWV system, including the piping serving the non-residential ground floor, is permitted to be constructed from abs.
Important Installation Requirements
Even though abs is permitted in this scenario, remember that its installation must still comply with all other code requirements, the most critical of which in a multi-story building is fire safety:
Firestopping: Every penetration of a fire-resistance-rated assembly (like the floor-ceiling assemblies between each story and any rated walls) must be protected with an approved firestop system. This is mandatory to maintain the fire separation between floors and occupancies.
In summary, a three-story building can be fully piped with abs for its DWV system because the number of residential stories does not exceed the two-story limit
set by the HCD.