Basin Installation

A tradesperson usually works in this order:

1. Measuring and marking. The height and position of the basin are set first. The top edge usually sits roughly 80 to 90 cm above the floor, adjusted to the people who will use it. At the same time, the fitter checks that the isolation valves and the waste pipe line up with the basin.
2. Drilling and fixing. Depending on the wall, the fitter chooses suitable plugs or a chemical anchor and sets the threaded studs or brackets. Holes through tiles are drilled slowly and carefully so the tile does not crack.
3. Fitting the tap. It is much easier to mount the tap on the basin before it goes on the wall. Two flexible tap connectors are attached to it.
4. Hanging and levelling. The basin goes onto the fixings, is levelled with a spirit level, and the nuts are tightened gently so the ceramic does not crack.
5. Connecting. The flexible connectors go onto the isolation valves, then the waste outlet and trap are fitted and the trap is connected to the waste pipe in the wall.
6. Testing and sealing. The water is turned on and every joint is checked. Only then is the gap between basin and tiles sealed with sanitary silicone.

Wall-hung basin

A wall-hung basin hangs straight on the wall, so the fixings carry all the weight. It needs a solid wall such as concrete or solid brick. On plasterboard or a lightweight partition, there must be a timber noggin or a mounting frame inside the wall, otherwise the basin will work loose over time. The upside: the floor underneath is easy to clean and the bathroom feels more open.

Basin on a vanity unit

The unit hides the trap and the pipes and gives you storage. The unit must stand or hang straight and firm, and the basin has to sit exactly on top of it. The back panel often needs cut-outs for the trap. Sealing the cut edges protects them from moisture, so the board does not swell later.

Inset, semi-recessed and countertop basins

These basins sit in or on a worktop. The job is more demanding because the opening has to be cut precisely to the manufacturer's template, and the joint between basin and worktop must be sealed thoroughly. With countertop basins, check the height and reach of the tap. If the spout is too low or too short, water splashes outside the bowl.

The quickest case is a like-for-like swap: the new basin is a similar size, the isolation valves work and the waste is in the right place. These things make the job longer and more complicated:

• Hollow bricks, aerated concrete blocks or plasterboard without reinforcement, which need special fixings
• Old, seized isolation valves that have to be replaced
• A waste pipe at a different height from what the new trap needs, or old pipework that has to be altered
• Fitting a vanity unit, cutting a worktop, or a wall-mounted tap with concealed pipework
• Thick or brittle tiles that are slow to drill

In a block of flats, remember that the waste and supply pipes connect to shared risers. If the work touches a riser, or the water has to be shut off for the whole building, agree it in advance with the building management or owners' association. For a larger bathroom refit with changes to the pipework, check with your local building authority before you start whether any approval is needed under local building regulations.

• Weak fixings. Standard plugs in hollow brick without a chemical anchor pull out over time. Choose fixings for the wall you actually have, not whatever came in the box.
• Overtightened nuts. The ceramic cracks at the bolt, often weeks later. Tighten gently and always use the washers.
• Reusing the old trap and seals. It saves a few minutes, but this is where leaks usually start. A new basin deserves a new trap and new seals.
• The wrong sealant. Ordinary acrylic, or silicone without a fungicide, soon turns black in a bathroom. Use sanitary silicone.
• Sealing before testing. If a leak shows up after sealing, the silicone has to be cut out again. Test with water first, then seal.
• A basin and tap that do not match. Before buying, check the number and size of tap holes and the length of the spout.

If you are swapping for a similar basin, the wall is solid and the isolation valves close properly, you can do this yourself. If you are unsure about the wall or the valves, call a plumber. You will need a spirit level, a drill, spanners, sanitary silicone and a new trap.

1. Close the isolation valves and open the tap to release the pressure.
2. Put a bowl under the trap, then unscrew the trap and the flexible connectors.
3. Cut out the old silicone, loosen the nuts and lift the old basin off carefully, ideally with a second person.
4. Check the old fixings. If they are loose or do not match the new basin, mark and drill new holes and fit fixings suited to the wall.
5. Fit the tap, waste outlet and connectors to the new basin following the manufacturer's instructions.
6. Place the basin on the fixings, level it and tighten the nuts gently.
7. Connect the flexible hoses to the isolation valves and fit the new trap.
8. Open the valves slowly, fill the basin to the top, let it drain and check every joint with a piece of kitchen paper.
9. Once the test is dry, clean and degrease the joint against the tiles and seal it with sanitary silicone.
10. Let the silicone cure as the manufacturer states, usually about a day, before normal use.

Before you accept the job, check that:

• The basin is level and does not move when you press on it
• The height and position match what was agreed
• There are no cracks or chips in the ceramic around the bolts
• Nothing drips from the trap, waste or connectors when the basin is filled and emptied
• The isolation valves open and close and are easy to reach
• Water drains smoothly and there is no smell from the waste
• The tap is firm and hot and cold are on the correct sides
• The silicone joint is continuous, smooth and without gaps
• The area is clean and you have the instructions and guarantee documents for the basin and tap