Installing or replacing a kitchen sink: drop-in, top-mount or undermount

The kitchen sink is the most used element in the room, and replacing it instantly transforms its look. Whether it is cracked, chipped, too small or simply outdated, changing a sink is an operation within reach of an average DIYer, provided you choose the right model and follow a few watertightness rules. In general, allow a full afternoon for a complete removal and installation, plus a budget of 60 to 400 euros depending on the material and size.

Choosing your sink type

• The drop-in sink: the most common, fitted into a cut-out in the worktop and held in place by mounting clips
• The top-mount sink: fixed directly onto a cabinet, with no cut-out, ideal for a simple replacement
• The undermount sink: flush with the worktop surface, it offers a seamless surface that is easy to clean
• The materials: stainless steel (the most common, from 80 to 300 euros), resin or composite (wide choice of colours), ceramic or fireclay (premium and fragile)

The drop-in model requires cutting the worktop, which can be daunting on a laminate but remains very doable with a jigsaw and a template. The top-mount model, on the other hand, sits directly on the cabinet with no cut-out at all: it is the simplest choice for a like-for-like replacement. If your worktop is stone or quartz, avoid cutting it yourself and prefer a top-mount sink, or have the cut made by a professional. Also check the cabinet depth under the sink: a sink 18 cm deep does not fit everywhere, especially if it must accommodate a waste disposal unit or a bulky trap.

The necessary tools

• Adjustable spanner or open-end spanner to unscrew the fittings
• Flat-head or Phillips screwdriver and water pump pliers
• PTFE tape for the threads, sealant paste or neutral silicone for the watertightness
• A bucket and old rags to catch the residual water
• New or disassemblable trap, drain hose and drain basket matching the sink
• Jigsaw and cutting template if you are installing a drop-in sink

Removing the old sink

1. Close the hot and cold water supply valves under the sink and open the faucet to drain the pipes.
2. Unscrew the connection hoses from the faucet or the valves, over the bucket.
3. Unclip or unscrew the trap and detach the drain hose from the waste pipe.
4. Remove the mounting clips or lift off the top-mount sink by pulling it straight up.
5. Clean the area: worktop cut-out, exposed edge, and check the condition of the floor under the cabinet.

Fitting and connecting the new sink

1. Apply a bead of neutral silicone around the cut-out if the sink is drop-in, or on the cabinet edge for a top-mount model.
2. Set the sink in place, then tighten the clips alternately and progressively for a perfect seat.
3. Install the drain basket with its gasket, on the top and bottom side, following the manufacturer's instructions.
4. Connect the trap and the drain hose respecting the fall, with no kink or back-fall.
5. Connect the hot and cold water hoses, tightening by hand then a quarter turn with the spanner.
6. Open the valves slowly and check every joint, including under the drain basket.

Checking the watertightness

Watertightness is tested in two steps. First, turn on the water and let it run over the plugged drain basket: check that no drop escapes under the sink. Then run a large amount of water and inspect the trap and its gaskets. If you spot a leak, unscrew, reposition the gasket and retighten moderately: most leaks come from a twisted gasket or excessive tightening, never from too little tightening. Let the silicone dry for 24 hours before putting the sink into service for a fully watertight seal.

The mistakes to avoid

• Forgetting to close the valves before removal, a cause of preventable water damage
• Over-tightening the fittings, which crushes the gaskets and causes leaks
• Neglecting the fall of the trap, which stagnates and gives off odours
• Choosing a sink too deep for the cabinet, which blocks the trap or the drawer
• Cutting too tight a cut-out in the worktop, which weakens the area around the sink

Installing or replacing a kitchen sink is a rewarding job that refreshes the whole room at a reasonable cost. The top-mount sink is the simplest for a replacement, while the drop-in sink requires a careful worktop cut. If your home is old and the pipes are hard to reach, or if you need to modify the drainage, ask a plumber for advice: connecting onto existing networks can hold surprises. In the case of a like-for-like replacement onto existing supply lines, a dedicated DIYer will finish the job in one afternoon.