How to install a vanity unit

Changing a vanity unit will give your bathroom a fresh look

In this guide we'll show you how to install a vanity unit and wall cabinet in your bathroom. With our easy to follow steps you can easily update the look of your bathroom.

There are 5 parts to this project:

  1. Remove the old installation

  2. Install the new vanity unit
  3. Install the washbasin
  4. Connect the water supply and drain
  5. Install the wall cabinet and lighting
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Turn off the electrical power and water at the mains before you start work on the electrical or water circuits.

Open the hot and cold taps to drain off any water remaining in the pipes before removing the old washbasin. Get help to lift the basin and remove the pedestal.

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Place a bowl under the siphon then unscrew and remove it.

If the water pipes under the washbasin are fitted with shut-off valves, close them. Unscrew the hoses from the pipes using an adjustable wrench and a pipe wrench.

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Cut through the silicone sealant around the washbasin. Use a ratchet wrench to unscrew the fixing nuts underneath the washbasin.

Remove the washbasin. Remove the wall brackets.

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To remove the old wall cabinet and its lighting, lift the cabinet off the wall just enough to get at the electrical wiring.

Remove the junction box face-plate and loosen the cable clamp.

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Use a mains tester screwdriver to check that the terminals are not live. Disconnect the wires from the terminals. Unscrew and remove the wall brackets for the old cabinet.

Finish by removing all traces of sealant from the wall using a silicone removing tool.

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You’ve now completed the first step.

If your new vanity unit isn’t going to hide the old fixing points, fill in the holes and redecorate the wall.


For easy access, the top of your washbasin should be between 85cm and 92cm from the floor.

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Once you’ve assembled the vanity unit according to the manufacturer’s instructions, get help to turn it upside down on the floor.

Screw the feet in firmly so that they support the weight of the unit. If the bathroom wall is reinforced or solid, it’s not essential to fit the feet.

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Measure the total height of your new vanity unit, including cabinet, feet and washbasin.

From this measurement, deduct the distance between the top of the washbasin and the top of the cabinet, then deduct the distance between the top of the cabinet and the centreline of the wall fixing points.

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Mark the resulting height on the wall then draw a horizontal line through it using a spirit level.

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Next, find where the centre of your cabinet is going to lie along the line you’ve just drawn. Mark this point.

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Measure the horizontal distance between the two fixing points on the back of the cabinet. Divide this figure by two then mark this measurement on the wall to either side of the mid-point mark.

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Use a pipe and cable detector to make sure there are no obstacles in the wall at these points. Move your markings if necessary.

Hold a wall bracket over the fixing point at one end of the horizontal line and mark the position of its holes. Repeat at the other fixing point.

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Drill holes in the wall at these points. Fit anchors of a type suitable for the wall. Screw the wall brackets into place.

Rest the cabinet on the wall brackets following the manufacturer’s instructions.

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Use a spirit level to check that the cabinet is perfectly level. Adjust the wall brackets if necessary. Once the cabinet is correctly positioned, tighten the bracket fixing screws.

Complete the job by adjusting the cabinet feet to distribute the weight evenly.


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First of all, fit the mixer. Fit the seal and screw in the threaded studs. Next screw on the water supply hoses.

Fit the mixer in its seat in the washbasin.

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Fit the mixer retaining rings to the threaded studs. Fit the rubber ring first and then the metal one.

Screw the lock-nuts onto the studs by hand. Use a tap wrench to turn them further but do not tighten yet.

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Check that the mixer is properly aligned in the centre of the washbasin, then tighten the fixing nuts.

Fit the drain fitting to the washbasin, following the manufacturer’s instructions. Fit and tighten the ring-nut. Now fit the overflow pipe to the washbasin.

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Connect the overflow pipe to the drain fitting. Screw the siphon into place under the drain fitting but do not tighten yet.

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Install the washbasin on top of the cabinet. Apply a bead of silicone around the top of the cabinet before lowering the washbasin into place.

Your washbasin is now installed.


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Start by screwing the mixer supply hoses to the unions on the water pipes. Make sure you know which is the cold and which is the hot.

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In the installation shown here, the old drain elbow is 40mm in diameter while the siphon outlet is only 32mm.

In cases like this, an adapter needs to be fitted.

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Cut the old drain connection off below the elbow using a PVC pipe cutter. Sandpaper the remaining end of the drain pipe.

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Take a sleeve and sandpaper the inside at both ends. Apply PVC adhesive and fit the sleeve over the end of the pipe. Sandpaper the adapter, inside and out.

Apply adhesive to the sleeve then insert the adapter as far the stop.

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Insert a length of PVC pipe into the adapter. This must be long enough to reach, or better still, pass the siphon outlet.

Insert another length of pipe into the siphon outlet.

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Hold an elbow over the two lengths of pipe. Mark where the horizontal pipe needs to be cut. Remove the pipe from the siphon and cut it at the mark.

Sandpaper both ends of the pipe.

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Re-insert the pipe in the siphon outlet. Hold the elbow in place over the vertical pipe and mark where this needs to be cut.

Remove the vertical pipe and cut it at the mark. Sandpaper the two ends of the pipe, then sandpaper the insides of the elbow.

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Assemble the pipe sections and elbow without adhesive. Align the elbow and see how far the pipes need to be pushed in.

Mark the pipes at these points.

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Disassemble the pipes and apply adhesive.

Apply PVC adhesive to the adapter, then push the vertical pipe in as far as the mark. Apply adhesive to one end of the elbow and fit this to the vertical pipe.

Apply adhesive to the other end of the elbow and fit the horizontal pipe.

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Fit the siphon’s lock-ring and its conical seal to the horizontal pipe. Screw the lock-ring onto the siphon.

Tighten both the siphon’s lock-rings to test for leaks.

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Turn the water supply back on at the mains and open the shut-off valves under the washbasin, if fitted.

Check that the hot and cold water connections are watertight. Tighten the lock-nuts again if necessary.

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To check the drain connections, close the plug and fill the washbasin with cold water as far as the overflow.

Check that the overflow pipe does not leak. Tighten the lock-rings if necessary.

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Empty the washbasin. Check all the drain connections for leaks.

If you find a leak, dry the connections and tighten the siphon rings or apply a generous quantity of adhesive to the outside of the PVC pipe connections. Finally, complete the assembly of your vanity unit.


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To get it in the right place, the bottom of the mirror should be at least 30cm above the level of the washbasin.

To locate the wall cabinet fixing points, measure the height of the brackets from the bottom of the cabinet and add 30cm.

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Find the centreline of the cabinet on the wall and mark the height you’ve just calculated. Now draw a horizontal line on which to mark the wall bracket fixing points.

Hold an edge and a spirit level at the central mark to draw the horizontal line.

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Measure the horizontal distance between the two fixing points on the cabinet.

Divide this figure by two, then mark this measurement on the horizontal line to either side of the mid-point mark.

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Use a pipe and cable detector to make sure there are no obstacles in the wall at these points. Move your markings if necessary. Hold a wall bracket over one of the marks and mark the drilling points. Repeat for the other bracket.

Drill the wall, insert anchor plugs of a suitable type then screw the brackets into place.

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Fit the light-bulbs to the cabinet then rest the cabinet on the washbasin to make the electrical connections. Pass the electrical cable through the junction box face-plate and through the cable grip.

Tighten the grip to hold the cable in place.

Use a mains tester screwdriver to check that the terminals are not live. Connect the wires to the terminals according to the wiring colour code. Check that the connections are secure by pulling gently on the wires. Fit the cable grip in the junction box and screw it into place. Fit the face-plate to the junction box.

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Lift the wall cabinet on to its brackets. Use a spirit level to check that the cabinet is level. Adjust the brackets if necessary, then tighten them firmly in place.

Switch electrical power back on.

Check that the cabinet lights work. Fit the cabinet shelves and doors.

Apply a bead of silicone between the washbasin and the wall. Use a sealing tool to smooth out the silicone.


Our installation service

Don't want to do it yourself? We can help. We work with approved installers to help coordinate your bathroom project from start to finish. Our range of flexible finance options means you can find a plan to suit you. We also provide a 2-year workmanship guarantee for peace of mind. Find out more about our installation service and book a free planning appointment to get started.