Baths, Toilets, Sinks & Taps

How To Install A Basin Or Bath

Difficulty rating: High

Likely to be quite challenging, these tasks should only be attempted by an expert or when supported by experienced advice and guidance.

Before you get started on any of our ‘how to’ guides, please take a moment to read through our DIY safety tips.

What You’ll Need:

1. Be aware of regulations

Follow these safety regulations and smart ways of working to protect yourself against hazards:

  • When doing plumbing, always put isolation valves on the hot and cold water pipes for each appliance if they’re not already fitted. With them you can easily isolate bathroom taps and appliances from the water supply without turning off the water at the mains.
  • You’re legally obliged to prevent contamination of the main water supply. Do this by installing double-acting non-return valves in the cold and hot water pipes if they’re fed by a direct hot water system.
  • Replace any of your supply pipes if they’re lead, as lead is toxic. Use copper or plastic pipes instead. You may need a qualified plumber for this.
  • Bond all metal pipes and fittings to a good earth, including any metal pipes and fittings on the bath and bathroom or kitchen sink. Plastic pipes and fittings must be bridged to ensure earthing continuity.
  • Make sure your waste pipes have room for a gentle fall (slope) into the main soil pipe or into a drain.
  • Building Regulations say you must fit an extractor fan if your bathroom has no windows. See our ‘How to fit an extractor fan’ guide for details.
  • If you’re unsure about any of these rules talk to a qualified plumber or your local council.
  • With any plumbing work always follow the manufacturer’s instructions.
Helpful Hint...

Plumbing work involving pipes is covered by a number of regulations. If you’re unsure about them, talk to a professional plumber.

2. Removing your old bath and sink

  • Turn off your hot and cold water at the mains (or isolation valves if they’re fitted) and drain the system. Make sure all remaining water is drained by turning on the bath and sink taps.
  • Remove the bath panels and any supporting framework.
  • With an adjustable tap spanner unscrew the taps and waste outlets from the bath and sink. Cut through the pipes if the nuts won’t undo, but leave ample pipe for future connections.
  • Undo the screws holding the sink to the wall and lift it away. You’ll need two people for this.
  • Remove the pedestal from the floor. This might be held in place by screws. If they’re rusted in, break the pedestal and then remove the screws with a mole wrench or hacksaw.
  • Adjust the feet to lower the bath. If it’s held against the wall with brackets, free it with a hammer and cold chisel
  • Dispose of your old bath and sink.
Helpful Hint...

When buying your bath or sink, check that the waste outlets and overflow units are supplied. If not, order the ones recommended by the manufacturer.

3. Preparing the new sink and pedestal

  • Fit the taps to the sink. Make sure they’re equally positioned at 90 degrees to the inner rim of the bowl of the sink. Put the flexible tap hoses on the tap tails.

fit the taps to the sink

  • Fit the waste outlet and waste trap and the bolt for the plug chain if needed.

fit the waste outlet and waste trap

  • Position the pedestal and place the sink basin on it. Adjust both until the basin is flat against the wall and sitting squarely on the pedestal. To do this, you might need to put thin wedges of vinyl tile under the pedestal and putty between the basin and the pedestal.
  • Mark the positions of the pedestal and its screw holes onto the floor.
  • Also mark the position of the basin fixing holes on the wall.
  • Make a note of the measurements for any adjustments needed.
  • Remove the basin and pedestal again.
Helpful Hint...
All shower areas need fan-assisted extraction, according to Building Regulations. Opening your bathroom windows isn’t enough. All work has to follow Building Regulations and IEE (Institution of Electrical Engineers) Wiring Regulations.

4. Fixing the basin and pedestal

  • Drill pilot holes for the floor fixing screws and drill and plug the wall for basin fixing screws.
  • Adjust the water and waste pipes as necessary.
  • Re-position the pedestal and screw it into place. Don’t drive the screws fully home yet.
  • Position the basin, checking that it’s level (use a spirit level) and adjust if you need to. Then screw the basin to the wall.
  • Use masking tape to cover the pedestal base and inject silicone sealant under the base. Trim off any excess sealant immediately, before it dries. Tighten the pedestal screws.
  • Connect the waste pipe to the trap and the flexible connectors to the waste pipes.
  • Turn on the water and check for leaks. If there are leaks then check the connectors and tighten them if necessary.
Helpful Hint...
If you’re breaking up an old cast iron bath, cover it with a thick dust sheet to stop pieces flying. Use a heavy hammer. Wear protective clothing, including gloves, stout shoes and safety glasses.

5. Preparing the new bath

  • Assemble your bath according to the manufacturer’s instructions. Do this on a clean, level surface covered in old carpet or underlay to protect the rim.
  • Fit any side handles now as they can’t be tightened once the bath is in position!
  • Install the waste outlet and overflow. Don’t forget to use silicone sealant.
  • Stand the bath on its feet and fit the taps.

position the bath and make markings for fixing plates or brackets

6. Positioning the bath

  • Following the manufacturer’s instructions, position the 47mm x 125mm timber that the bath will stand on. This spreads the load of your bath and should be laid at 90 degrees to the floor joists (see image above).
  • Position the bath and adjust the feet until all the top edges of the bath are level and at the right height. Check with a spirit level along the length and across the width of the bath.
  • Mark the holes for the wall fixing plates or brackets (see image above).
  • Fit the waste trap and note any adjustments needed to make it fit the waste pipe (see image below).
  • Fit the flexible tap connectors and mark the water pipes where they need to be cut (see image above).
  • Mark the position of the timber supports and then remove the bath.
  • Screw down the bath’s timber supports in the marked positions.

fit the waste trap

7. Fixing the bath in place

  • Drill and plug the walls for the wall fixing brackets.
  • Adjust the waste and water pipes if you need to.
  • Double check the tap and handle connections. Tighten the flexible tap connectors onto the tap tails.
  • Remove any protective film from the return edges of the bath that are next to the walls.
  • Degrease the return edges with cellulose thinner and fine wire wool, then dry them thoroughly.
  • Reposition the bath and check it’s still level.
  • Inject silicone sealant between the walls and the bath.
  • Screw the fixing brackets to the wall and the feet to the floor.
  • Connect the waste trap to the waste outlet and waste pipe.
  • Connect the flexible tap connectors. Make sure they’re not kinked or twisted.
  • Turn on the water and check for leaks.

8. Sealing around the bath

  • When you tile down to the bath rim, leave a 3mm-4mm gap between the tiles and the bath.
  • After you’ve finished tiling and the grouting is dry, mask the bath and tiles with masking tape.
  • With the bath full of water, inject silicone bath sealant to completely fill the gap. Smooth off and remove the masking tape within 20 minutes.
  • Leave the water in the bath for a minimum of six hours to allow the sealant to dry.

9. Earthing all metal work

Attach earth bonding cable and clamps to all metal pipework and fittings as it reduces the risk of electrocution. It’s also a legal requirement. Remember to bridge plastic pipework, too.

Plastic pipes and fittings must be bridged to ensure earthing continuity



Writer and expert