What NB code requirements apply to a garage with floor drains connected to a dry well?

Floor drains in NB garages require careful compliance with both the National Building Code and provincial plumbing regulations, and connecting to a dry well (soakaway pit) has specific restrictions that many homeowners don't realize.

Under the NB Building Code and National Plumbing Code, garage floor drains are permitted but must meet strict requirements. The drain cannot connect directly to the sanitary sewer system because garage runoff may contain oil, gasoline, antifreeze, and other automotive fluids that contaminate wastewater treatment systems. Instead, garage floor drains must connect to an oil/water separator before any discharge, or drain to an approved disposal system like a dry well.

Dry well connections for garage drains are regulated under NB's on-site wastewater disposal regulations. The dry well must be located at least 5 feet from any building foundation, 10 feet from property lines, and 100 feet from any water well or surface water body. In many NB residential lots, especially in Moncton, Saint John, Fredericton, and other urban areas, these setback requirements make dry wells impractical or impossible. The dry well must also be sized appropriately for soil conditions — sandy soils drain well, but NB's common clay soils may not provide adequate infiltration, causing the system to back up or overflow.

Soil percolation testing is typically required before installing a dry well system. The soil must demonstrate adequate drainage capacity to handle the expected volume of water from vehicle washing, snow melt, and precipitation that enters through the overhead door. In areas with high groundwater or poor drainage — common in low-lying areas of the Saint John River valley, Petitcodiac River valley, and coastal communities — dry wells may not be approved at all.

Municipal requirements vary significantly across NB. Some municipalities prohibit garage floor drains entirely, others require oil/water separators regardless of the discharge method, and some have specific design standards for dry wells. Fredericton, Moncton, Saint John, and Dieppe each have different interpretations of how garage drainage should be handled. Rural areas under provincial jurisdiction may have different requirements than incorporated municipalities.

Practical considerations make garage floor drains problematic in NB's climate. The drain and connecting piping must be installed below the frost line (4-5 feet deep) or they'll freeze and crack during winter. This means expensive excavation and the drain line must slope continuously from the garage slab to the dry well without any low spots where water can freeze. Many contractors recommend against floor drains in unheated garages because of freeze risk and maintenance issues.

Alternative approaches are often more practical in NB. A threshold drain at the garage door opening captures most water and snow without requiring a floor drain. Sloping the slab toward the door (1/4 inch per foot minimum) allows water to drain naturally outside where it won't freeze in the piping system. For heated garages where floor drains are desired, connecting to a sump pit with pump discharge to a remote dry well may be more reliable than gravity drainage.

Before installing any garage drainage system, contact your local building inspection department and obtain proper permits. The system must be designed by someone familiar with NB soil conditions, frost depth, and local regulations. Many garage contractors subcontract this work to plumbing professionals who understand the code requirements and can design a system that won't freeze, back up, or violate environmental regulations.

When to hire a professional: All garage drainage work requires professional design and installation. The excavation, piping, dry well construction, and connections involve multiple trades and must comply with building, plumbing, and environmental codes that vary by municipality.

Need help finding a professional garage builder familiar with NB drainage requirements? New Brunswick Garages can match you with experienced contractors through the New Brunswick Construction Network.