Quick Answer
Water, sewer, and hydro are run to a backyard garden suite by trenching from the existing house connections across the yard to the new building. Water and electrical typically branch off the main house service, while sewer either gravity-drains to the existing lateral or uses a sewage ejector pump if the suite sits lower than the municipal main. The work needs municipal building, plumbing, and electrical permits plus inspections, and is one of the biggest line items in a garden suite budget.
The standard approach: trench services from the main house
In most GTA garden suite projects, water, sewer, and hydro are extended from the existing house rather than from brand-new street connections. A trench is dug across the backyard from the house to the suite, and the three services run through it at code-required depths and separations. Domestic water usually taps off the home's main water line, often upsized so both the house and suite have adequate pressure and flow. The electrical feed runs underground from the existing panel or a new sub-panel, sized for the suite's load. Sanitary drainage connects into the home's existing sewer lateral that already serves the municipal main. This shared-service approach is generally far cheaper and faster than applying for separate metered street connections, which can require road cuts, municipal approvals, and significant fees. Whether you can share or must install independent services depends on capacity, your municipality's rules, and the suite's size. Because the trench, backfill, and underground work happen before framing, servicing is sequenced early. Leo Constra coordinates the excavation, plumbing, and electrical trades so the trench is opened, inspected, and closed once rather than multiple times.
Sewer: gravity drainage versus an ejector pump
How sewage leaves a garden suite depends on elevation. The ideal scenario is gravity drainage, where the suite sits high enough that wastewater flows downhill through sloped pipe into the home's existing sanitary lateral and out to the municipal sewer. Gravity is simpler, cheaper, and has no moving parts to fail. When the suite's plumbing fixtures sit below the level of the sewer main, which is common with slab-on-grade suites or deep municipal lines, a sewage ejector or grinder pump is installed. The pump collects waste in a sealed basin and lifts it up to the gravity line. Ejector systems add cost and require power, a backup plan, and ongoing maintenance, so an early grading and elevation assessment matters. Storm drainage and the suite's roof runoff are handled separately and must follow your municipality's lot-grading and stormwater rules. Connecting into the existing lateral also means confirming that pipe has the capacity and condition to handle the added fixtures. We recommend a camera scope of the existing lateral before committing to a connection plan, since an old or cracked clay line may need replacement anyway.
Hydro and water: capacity, panels, and metering
Electrical service to a garden suite is run underground from the main house and almost always requires evaluating whether the existing service is large enough. Many older GTA homes have 100-amp service that cannot comfortably carry a second full dwelling, so an upgrade to 200 amps, or a dedicated sub-panel in the suite, is frequently part of the scope. The local utility, such as Toronto Hydro, Alectra, or Hydro One depending on your city, sets the rules for service size and whether the suite is separately metered. Separate metering lets a tenant pay their own electricity but adds cost and utility coordination; many owners instead sub-meter privately. On the water side, the existing service line and meter must handle both buildings, and your municipality may require a larger line or backflow protection. Confirm metering, service-size, and connection requirements with your utility and municipality before finalizing the design, because these decisions drive both budget and timeline. Leo Constra handles the permit drawings and inspection bookings so the underground electrical and water work passes the first time and the suite energizes on schedule.
Permits, inspections, and what servicing costs
Running services to a garden suite requires municipal permits and a sequence of inspections, and it is one of the larger cost drivers in the project. You will typically need a building permit plus plumbing and electrical permits, and the underground trench gets inspected before it is backfilled so the connections and depths are verified. Ontario now allows up to three units per lot as-of-right in most municipalities, and four in Toronto, which has made backyard suites far more common, but each city still enforces its own servicing, grading, and connection standards. Confirm the exact permit and inspection requirements with your municipality before you dig. A full garden suite in the GTA typically runs from roughly $180k to $400k or more, and the servicing portion, the excavation, trenching, plumbing, sewer, and electrical, is a meaningful share of that, especially if a sewage ejector pump or a hydro upgrade is needed. These figures are estimates only; we provide a real quote after a site visit, and HST is extra. Bill 23 also exempts many qualifying second units from development charges, often saving tens of thousands, so confirm current details with your city.
Have a project in mind?
Get a free, no-obligation quote from Leo Constra’s licensed team—20+ years of renovation experience across the GTA, backed by a 2-year workmanship warranty.
Get a Free Quote