How much does it cost to run water lines to a detached garage in Ottawa?

Running water to a detached garage in Ottawa is a significant plumbing project that typically costs $5,000 to $15,000 depending on the distance from your house, the depth of the trench, soil conditions, and whether you need both supply and drain lines. It is one of the most frequently asked-about upgrades and one that requires careful planning due to Ottawa's deep frost line.

The primary challenge is frost protection. Ottawa's frost line sits at 1.2 to 1.5 metres below grade, and any water supply line running between your house and detached garage must be buried below that depth to prevent freezing. For a typical suburban lot where the garage sits 10 to 20 metres from the house, this means trenching a significant length of trench at roughly 5 feet deep. Excavation costs for this trench typically run $2,000 to $5,000 depending on length, soil type, and what is in the way — tree roots, existing utility lines, concrete walkways, or landscaping that needs to be removed and restored.

The supply line itself is usually 3/4-inch or 1-inch PEX (cross-linked polyethylene) run inside a protective conduit. PEX is the standard choice for underground residential water lines in Ottawa because it is flexible, resistant to freeze damage (it can expand slightly without cracking), and easy to route. The material cost for PEX and fittings is modest — a few hundred dollars for most runs — but the labour and excavation are where the money goes. Some contractors also insulate the pipe within the trench using foam pipe insulation or heat trace cable as additional freeze protection, which adds $500 to $1,500 depending on the length.

If you need drain and waste lines (for a sink, floor drain, or bathroom — more on that in a moment), the project becomes more complex. Drain lines require proper slope for gravity flow (typically 1/4 inch per foot of run) and may need to connect to your home's existing drain system or to a separate holding tank or dry well depending on your lot's municipal services. Tying into the house drain often requires interior work in the basement, cutting into the existing drain stack, which adds $1,500 to $3,000 to the project. All drain connections must be inspected and meet the Ontario Building Code.

A simpler and more affordable alternative for garages that only need water for occasional use — washing hands, filling a bucket, rinsing tools — is a frost-free hydrant or yard hydrant installed outside the garage and fed from the house. These self-draining hydrants cost $800 to $2,000 installed and eliminate the risk of frozen pipes entirely since the shut-off valve sits below the frost line and the upper column drains automatically when closed. The limitation is that it provides cold water only at a single outdoor point, not plumbed fixtures inside the garage.

Another option gaining popularity is a hot water recirculating loop for garages that need both hot and cold water. Rather than running a separate hot water line from the house (which would cool down in the long underground run and waste water waiting for hot to arrive), an on-demand tankless water heater in the garage costs $2,000 to $4,000 installed and provides instant hot water from the single cold supply line.

All plumbing work in Ontario must be done by a licensed plumber and requires a plumbing permit from the City of Ottawa. The permit ensures the work is inspected and meets code for cross-connection prevention, backflow, and proper drainage.

Ottawa Garages can connect you with builders and plumbers who handle the full scope of running water to detached garages, from trenching to final inspection.

---

Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• Dump n Dash Hauling
• ALTIOR CONSTRUCTION
• Ottawa Garage Doors & Openers