Introduction

Bathroom washbasin can be either mounted directly to the wall using purpose built brackets, or they can me mounted into the top of a vanity unit. Mounting under a unit may be more fiddly to plumb in a confined space, however the advantage of increased storage space can make it worthwhile

Tools for the job

To fit a washbasin, you will need the following;

Removing the old basin

Before attempting to remove the existing washbasin, turn off the mains water supply and if possible isolate the inlet supply to the basin.

If you are planning on installing a brand new bathroom then a huge amount of care is not entirely necessary as the majority of plumbing will be replaced, however if you are planning on simply replacing the washbasin only then do the following:

• Loosen all compression joints to the taps, and disconnect the waste trap from the base of the washbasin.
• If you are planning on keeping the existing plumbing points then leave at this, however if new plumbing is required, cut through the waste and supply pipes at a place that makes connecting new plumbing an easier task (ie not immediately below the basin).
• Remove any fixings holding the washbasin in place, either against the wall or within a vanity unit, and lift the washbasin free.

Fitting new washbasin to the wall

• Due to the weight of most washbasins, it is advisable to acquire the services of an assistant to help hold the washbasin in place.

• Hold the new basin against the wall in the desired location and ensure it is level by using a spirit level.
• If you are installing a pedestal washbasin, place the pedestal against the wall and then sit the washbasin on top of it, this will ensure that washbasin is at the correct height.
• Mark the position of the fixing points on the wall using a pencil.
• Drill and plug the holes, then attached the washbasin to the wall.

Fitting new washbasin within a vanity unit

• Cut a hole in the unit for the washbasin, by either tracing around the template supplied with the washbasin, or by turning the washbasin upside down in the desired position on the worktop and drawing around the edge with a pencil. Mark a line 10mm (3/8in) inside the original line to create a supporting ‘lip’ for the washbasin to sit on, then drill a 10mm (3/8in) hole reasonably close to the inside line and then use the jigsaw to cut out the remaining shape, creating rounded corners to avoid splits.
• Sit the washbasin in its hole and mark the position of the taps and the waste pipes onto the wall. Remove the washbasin and extend supply and waste pipes to these marked areas as necessary.
• If applicable, cut tap hole(s) into the washbasin. Cover the desired tap position with masking tape and make a small hole in the centre with a centre punch. Use increasingly large drill bits (masonry bits for ceramic washbasins, metal bits for stainless steel) on this hole to widen the gap to the desired diameter for the taps.
• Assemble the taps and waste outlet onto the washbasin before it is positioned into the unit. Fit short copper tail pipes to each tap to make later installation and connection to supply easier.
• To create a watertight seal, turn an inset washbasin upside down and run a line of silicone sealant around it's perimeter. This sealant should be on top of the lip for undermounted washbasins, and the sides of the washbasin for a sit on washbasin.
• Place the washbasin in position in the unit and fix it in place with the supplied brackets and screws.

Connecting the taps and waste trap

• Connect a bottle trap to the waste outlet of the washbasin. Connect the existing waste pipework to the bottle trap.
• If a new waste pipe is needed, either (two-pipe drainage system) run a new length of 32mm (1¼in) waste pipe through the wall with a fall of 6mm (¼in) per 300mm (1ft, 12in) to terminate over the hopper for the outside drainage pipe, or (single stack drainage system) connect the waste pipe to the existing soil pipe for the property (see below).
• Connect up the supply pipes to the taps, now is a good opportunity to add isolating valves to these pipes to make future servicing easier.
• Ensure the washbasin is earth bonded according to current IEE Wiring Regulations. Since water is a good electrical conductor, any electrical leakage (from a faulty circuit) will use any moisture to travel to earth. To prevent electrocution, all metal parts must be connected together with an earth wire (min 4mm) via an earth clamp which will collect current/voltage from the leak and equalise it around the metal parts. The other end of the earth wire should be connected to a local earth such as a close socket.

• How to fit a bathroom tap
• Building Regulations Part P: Electrical Safety

Attaching new waste pipe to soil pipe

The simplest way to achieve this is to strap a new boss to the outside of the soil pipe, and connect the waste pipe to this.

• Cut a hole, of the correct diameter, in the side of the soil pipe using a hole-saw.
• Smooth the edges of the new cut hole, and smear an adhesive around the edges.
• Place the boss over the hole, and afix in place with the adhesive. Tighten the strap using a screwdriver to permanently fix in position.
• Insert the appropriate rubber lining into the boss to allow the waste pipe to attach to the soil pipe.
• Use clips to hold the waste pipe to a wall to ensure that the pipework remains in position.

• Drainage systems

Further information and useful links

• Choosing a new bathroom Washbasin
• Common metal compression fittings & adaptors
• More plumbing & heating topics
• More bathroom topics

• Find a Plumbing Merchants near you
• Find a Plumber near you
• Find a Bathroom Fixtures & Fittings supplier near you

• Water Regulations Guide - (wras.co.uk)
• The Institution of Engineering and Technology for IEE regulations - (theiet.org)