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Most jobs are replacements in the same spot, which keeps the plumbing simple. Moving a sink, adding one to a kitchen island or putting a laundry sink in a basement with no drain nearby is a bigger project: the new drain needs the right slope and a vent, and the work may call for a permit.
Planning the sink together with the countertop, the faucet and the appliances around it avoids the classic problems: a bowl that doesn't fit the cabinet, a faucet that can't be mounted, or a drain set so low that the dishwasher struggles to empty.
Kitchen and bathroom sink types: undermount, drop-in, farmhouse, vessel and pedestal
- Drop-in or top-mount: the rim rests on the countertop, which makes it the easiest to install or replace and a natural fit for laminate; the joint between rim and counter does collect crumbs and grime.
- Undermount: the bowl is bonded and clipped under a solid countertop such as stone or quartz so you can wipe straight into it; it needs a counter with a finished cut edge, and replacing it later can disturb the countertop.
- Farmhouse or apron-front: a deep bowl with an exposed front that needs a sink base built or modified for it, with solid support underneath for its weight when full.
- Vessel: a basin sitting on top of the vanity; it needs a tall or wall-mounted faucet and a vanity low enough that the rim ends up at a comfortable height.
- Pedestal and wall-hung: a basin on a column or fixed to the wall, which frees floor space but hides almost nothing, so the trap and supply lines should be tidy and the wall needs solid blocking to carry the weight.
- Laundry and utility sinks: deep tubs on legs or in a cabinet, often in a basement, where the height of the nearest drain decides how easily the sink can be connected.
Coordinating a new sink with the countertop, cabinet and faucet
With a new countertop, the sink is chosen first, not last. The fabricator cuts the opening from the actual sink or its template, and an undermount bowl is usually mounted while the countertop is installed, before the plumber comes back to connect it. Faucet holes are drilled at the same stage, so settle on a single-hole faucet or a widespread set, a separate sprayer, a soap dispenser or a filtered-water tap before the counter is made.
Check the cabinet too. The sink base has to hold the bowl with room left for the drain, a disposal and the supply lines, and a deep or double bowl can leave very little space for the trap or a pull-out bin. When only the sink is changing in an existing counter, the new one has to match or cover the old cut-out; a plumber can tell you whether a different size or style will fit without new counter work.
Sink drains, P-traps and venting: why an old S-trap gets replaced
Every sink drains through a trap, the curved section of pipe that holds a little water to keep sewer gas out of the room. Under a sink this is a P-trap: the bend holds its water seal, and the trap arm runs sideways into the wall, where the drain ties into a vent that lets air in behind the flowing water. Without that air, water rushing down the pipe can pull the seal out of the trap, and you start to hear gurgling or smell the sewer.
Older homes sometimes have an S-trap, where the pipe loops down through the floor with no vent close by. It can siphon itself dry each time the sink empties, and where the plumbing code prohibits it, which is the usual case for new work, a plumber replacing the sink will convert it to a vented P-trap. On an island, or anywhere a wall vent is out of reach, ask the plumber which venting method the local code accepts before the layout is final.
Shut-off valves and supply lines under a new sink
A sink replacement is the right moment to deal with what feeds it. Each supply pipe should end in its own shut-off valve, one for hot and one for cold, so the sink can be isolated without turning off the whole house. Stiff or corroded multi-turn valves are worth replacing with quarter-turn valves while the cabinet is empty, and new braided supply lines should reach the faucet without stretching or kinking.
Kitchen sinks often feed more than the faucet: a dishwasher, a refrigerator water line or a filtered-water tap. A valve with a second outlet gives each appliance its own shut-off. In a laundry room, the sink usually sits beside the washer's valves, and a water alarm on the floor beneath them is a simple safeguard against an overflow or a burst hose.
Dishwasher and garbage disposal connections: getting the kitchen sink hookups right
A garbage disposal mounts to the sink's drain opening and grinds scraps before they go down the pipe, so it needs cabinet space, a drain layout that sends its discharge into the vented trap, and an electrical connection that an electrician should install. On a septic system, think twice: Quebec's good-practice guide for septic owners warns that a food waste disposer adds load to the tank and can mean more frequent pumping, and suggests composting scraps or putting them in the garbage instead.
On municipal sewers, a disposal still isn't a route for fats, oils and grease. The City of Toronto explains that grease poured down a sink cools, hardens and sticks to the inside of sewer pipes; it recommends letting grease harden and scraping it into the organics bin, and using a strainer in the sink to catch food scraps.
- Dishwasher drain hose: it needs a high loop under the counter, or an air gap where the local code calls for one, so dirty sink water can't flow back into the dishwasher.
- Disposal inlet: on a new disposal, the knockout plug in the dishwasher inlet has to be removed before the hose is connected, or the dishwasher won't drain.
- Dishwasher supply: its own shut-off or a dual-outlet valve, with a supply line long enough to slide the machine out for service.
- Leak check: once everything is connected, the sink, the disposal and a dishwasher drain are run while every joint in the cabinet is watched.
Permits for moving or adding a sink, and who does the work
Replacing a sink in the same place, on the same drain and supply, is generally treated as a fixture replacement. Moving a sink, adding one in an island, a bar or a basement, or running new drain and vent piping changes the plumbing system, and many municipalities require a permit and an inspection for that; check with yours before the walls or floor are closed up.
Quebec reserves plumbing work for holders of the plumbing licence issued by the Régie du bâtiment du Québec, which contractors obtain through the CMMTQ. In other provinces, the provincial licensing body and the municipality set the rules. The wiring for a disposal, an instant hot-water tap or under-cabinet lighting is electrical work for a licensed electrician.
Sink Installation: frequently asked questions
Can I replace a drop-in sink with an undermount sink?
Only if the countertop allows it. An undermount sink needs a solid surface with a finished edge around the opening, so it works with stone, quartz or solid-surface counters but not standard laminate. In an existing stone counter, the opening has to be recut and polished to suit the new bowl, which is a job for the countertop fabricator.
Who installs an undermount sink, the plumber or the countertop installer?
Usually the countertop fabricator or installer mounts it, since it has to be bonded and clipped to the stone. The plumber then connects the faucet, drain, disposal and dishwasher. Agree on who does what before the counter arrives, so the sink isn't left sitting unmounted.
Should I replace the faucet when I replace the sink?
It's often worth it. The faucet has to suit the new sink's holes or deck, and mounting it on the sink before the sink goes in is much easier than working upside down in the cabinet afterwards. An old faucet in good shape can be reused if it fits, but fresh supply lines are a sensible addition either way.
Why does my new sink gurgle or smell?
Gurgling as the sink empties, or a sewer smell under the cabinet, usually means the trap is losing its water seal: the vent may be missing or blocked, the trap arm may be too long or badly pitched, or a slip joint may be loose. A plumber can check the connection behind the wall as well as the trap itself.
Can a laundry sink go in a basement with no drain nearby?
Often, yes. If there is no drain low enough to run to by gravity, a small pump can lift the water to the house drain. The sink still drains through a trap that needs venting, so have a plumber lay out the drain, the vent and the pump together, and ask whether the work needs a permit.
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Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides