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Installing a bathroom sink

Cost: Difficulty:


Before starting it is important to consider the type of basin to install.

Select the type of taps to fit, either pillar taps or mixers (usually supplied with a pop-up waste) for function as well as style. Manufacturers often specify the British Standards Institute code number - BS 1010 - of taps for which their kits are suitable. If a code number cannot be found, it is usual that a British basin and British taps are compatible.

Decide which drainage trap to install and what plumbing system to use.


Decide on the location of the basin. The main consideration is running the waste to the waste stack of the house. The waste should not exceed 3metres (10 feet) in length. It should slope 6mm (0.25inches) for every 300mm (1 foot) of pipe run.

Allow enough room for leaning over the basin when washing and decide a sensible height for the basin to be sited. A helper should try the basin in different positions and heights. The average fixing height is between 28 and 32 inches high. When the position and height have been decided, check the horizontal position with a spirit level. Place a length of wood across the basin if a flat surface is required for using the spirit level. Use a pen or pencil to mark the wall at the basin fixing holes. Place a length of wood between the marks and check the horizontal distance with a spirit level before drilling and plugging the holes.

Inset basin or vanity unit

If you are fitting an inset basin or vanity unit, prepare the work top or surface first. Before starting to cut, the measurements should be checked carefully. If a template is not supplied with the basin, place the basin upside down on the surface and draw a template of the shape. Use a flat bit to drill a hole large enough for the jig saw blade. Score the cutting line and insert the jigsaw blade, then use the jigsaw to cut a hole in the surface/worktop.

Once cut, place the basin on the opening and check the size, making minor adjustments if necessary. Place mastic or sealing strip all round the outside of the hole. Push the basin firmly into position pressing all the way round to ensure a watertight seal. When you are satisfied the basin is sitting squarely in position, checking with a spirit level, tighten fixing clips underneath the surface, or inside the unit.

Pedestal Sink

If you are fitting a pedestal sink, get a helper to seat the basin on the pedestal and check the level. Mark the wall through the fixing holes. Remove the basin and pedestal before drilling and plugging the holes. Resting the basin on the pedestal very close to the fixing position make the waste and supply connections. Then carefully ease the pedestal and basin into position. Screw the basin to the wall and the pedestal to the floor.

Wall-hung basin or corner basin

If you are fitting a wall-hung basin or corner basin, ask a helper to hold the basin in position. The fixing position of the bracket should be marked on the wall. Fix the bracket to the wall securely either by engaging the adjustable hook, locating it over projecting bolt heads or screws. Place the basin on it and start connecting the fittings.

Connecting fittings

Equip the basin with its relevant fittings before installation. If possible install the tap connectors as well before siting, as their positions are difficult to plumb once the basin is attached to the wall as access is restricted.

Position the taps in the mounting holes with their washers or gaskets (supplied with the taps) in place on the tail of the taps. If no washers are supplied spread silicone sealant around the top of the tail and beneath the base of the tap. Rest the basin on its rim and slip a second washer onto the tail. Hand-tighten the back-nut in order to clamp the tap onto its basin.

At this stage check that the spouts are pointing into the basin and then tighten the back-nut carefully using a spanner. A cranked spanner is the best tool for this job as it fits basin and bath taps.

Place the waste outlet into the bottom of the basin. Most basins have an integral overflow system, i.e. the overflow is built into the sink and does not have an exterior overflow pipe. It is therefore important that the waste outlet is aligned correctly so that the overflow can empty correctly. The waste outlet should be fitted to the bottom of the basin with either washers or silicone sealant (to ensure that the sink is watertight). Holding the waste outlet in position, tighten the back-nut under the basin and then fix the trap to the end of the waste outlet. Finally, fit the other end of the trap to the existing waste pipe.

For connection instructions for new taps see Fitting new taps.

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