Should I plan for a floor drain when designing a garage in Riverview New Brunswick?

Yes, planning for a floor drain during the design phase is strongly recommended for a Riverview garage, especially if you intend to use the space for winter vehicle storage, workshop activities, or vehicle washing. Installing a floor drain during initial construction costs $500 to $1,200, while retrofitting one into an existing slab costs $2,000 to $4,000 or more because it requires cutting the concrete, excavating underneath, and connecting to an approved drainage system.

Riverview sits in the Petitcodiac River valley, an area that receives significant precipitation year-round — well over 1,100 millimetres annually — and has high water tables in many neighbourhoods, particularly in areas closer to the river and in lower-lying developments. Between November and April, every time you park a snow-covered vehicle in your garage, a considerable volume of water melts off the undercarriage, wheel wells, and tires. A properly sloped slab (1/8 to 1/4 inch per foot toward the overhead door) handles much of this drainage by directing water out the front. But a floor drain provides a backup drainage point that handles situations where the door is closed — which in a Riverview winter is most of the time, since you close the door to keep the cold out.

A floor drain is particularly valuable if you plan to wash vehicles inside the garage, clean equipment, or do any work that generates water on the floor. Without a drain, wash water has nowhere to go except out the overhead door — which means opening the door in winter and letting all your heat escape — or it sits on the floor and creates a humid, slippery environment. For workshop garages where you clean parts, mix concrete, or use water-cooled tools, a drain is essentially a necessity.

Plumbing Code and Drainage Requirements

In Riverview, a garage floor drain is subject to NB plumbing code requirements, and understanding these before you pour the slab will save you headaches. A floor drain cannot discharge directly to the municipal sanitary sewer in most cases unless it passes through an oil-water separator (also called an oil interceptor). This is because vehicle wash water contains petroleum products, road salt, and contaminants that the sanitary system is not designed to handle. An oil-water separator adds $800 to $2,000 to the installation cost but is required by code for any drain that may receive automotive fluids.

The alternative — and the more common approach for residential garages in Riverview — is to connect the floor drain to a dry well or soak-away pit. This is a gravel-filled pit buried adjacent to the garage foundation that allows water to percolate gradually into the surrounding soil. A typical residential dry well is 3 to 4 feet in diameter and 3 to 4 feet deep, lined with filter fabric and filled with clear crushed stone, with the drain pipe entering near the top. Cost for a dry well installation is $500 to $1,500 depending on soil conditions and size. In Riverview's clay-heavy soils in some areas, percolation rates may be slow, and a larger dry well or multiple pits may be needed — your contractor should assess soil conditions before sizing the system.

Every floor drain must include a P-trap to prevent sewer gas or ground odours from entering the garage. The challenge with garage floor drains is that they often dry out from infrequent use, breaking the water seal in the trap and allowing odours to enter. A trap primer — either a mechanical device connected to a nearby water supply line or a simple manual procedure of pouring a bucket of water down the drain every few months — keeps the trap sealed. Some NB plumbers install traps with built-in check valves that maintain the seal even when the water evaporates.

Placement of the drain matters. The most common location is near the centre of the garage or slightly toward the front, with the entire slab sloped toward it from all directions. This requires careful forming and finishing during the concrete pour — the slope must be consistent and directed toward the drain on all planes. Some homeowners prefer a trench drain (linear channel drain) across the full width of the garage just inside the overhead door, which intercepts water at the entry point before it spreads across the slab. Trench drains are excellent for garages on lots where the driveway slopes toward the building, a common situation in Riverview's hilly terrain.

If you are on the fence about whether to include a drain, consider this: the drain pipe, trap, and rough-in can be installed during the slab pour for as little as $500 to $800, even if you do not connect it to a drainage system immediately. This preserves the option to activate the drain later without breaking the slab. Backfilling around the rough-in is far less expensive than cutting concrete after the fact.

All plumbing work for a floor drain requires a permit and inspection in Riverview — your plumbing contractor handles this as part of the installation. Get matched with a garage contractor for a free estimate on your project through New Brunswick Garages.