Replacing an existing washbasin that is old, cracked or ugly is a simple procedure because you can utilize the existing plumbing and drainage. If you are installing a washbasin in a room that has never had one, then you’ll need to think about running new pipes. How the waste pipe runs to the vertical stack must also be taken into account: it must have a minimum fall or slope of 6mm (1/4in) for every 300mm (1ft) of pipe and should not be longer than 3m (10ft). In a straightforward replacement, there’s no need to worry, as you’ll be using the waste pipe that already exists.
When connecting new washbasins to your existing pipes, be aware that the sizes and materials may not match. You could find pipes in a variety of materials, especially if it is an older house. Modern plastic pipes are not yet standardized so those supplied by one manufacturer might not be compatible with another’s. Adapters can be purchased for joining pipes of different materials, and also for joining new metric pipes to old imperial-sized ones.
When you choose a new washbasin, you’ll need to decide on the type you want: wall-hung or pedestal are the most common types in domestic use. The hollow pedestal provides a little support for the basin, but mostly it just conceals the pipe-work. Old-style wall-mounted wash-basins were often hung on large metal brackets, but modern ones generally have concealed wall mountings. You will need to make sure, however, that the wall is strong enough to support the weight of the vitreous china they are made from. Make sure that the basin has holes at the required spacing to take the taps – you’ll probably want to replace these as well – or none at all if the taps are wall mounted. When you buy a new washbasin and taps, it’s a good idea to ‘dry test’ them: bend over the basin and imagine you are washing your face. Make sure you can get both hands in the bowl.
Removing & Replacing a Wall-Hung Basin
1 Turn off the supply
Turn off the water supply to the basin. If you are using the existing plumbing, loosen the compression nuts on the tap tails and the trap.
2 Cut through supply pipes
If you are not using the existing plumbing but running new pipes to a re-positioned replacement, cut through the waste pipe and supply pipes at a point convenient for taking new connections.
3 Remove fixings
Remove any fixings attaching the basin to support brackets or pedestal and carefully lift it away from the wall. Remove the wall brackets by applying a little penetrating oil to avoid damaging the plaster. If this fails, lever them off.
4 Fit the taps
Before you fix the new basin in place, fit the new taps. Manufacturers provide full instructions so follow them carefully. Make sure that the spouts face the right direction – into the basin – when you tighten them into place.
5 Fixing to the wall
Get a helper to hold the basin against the wall and check it is horizontal with a spirit level. Mark the position of the fixing holes for the wall bracket. Drill and plug the fixing holes, then secure the bracket to the wall and hold the basin to it with the supplied fixings.
6 Adding a wall batten
If, when you remove the old sink, you find that the wall behind the basin is damaged – perhaps from water splashes over the years – reinforce the wall with a stout wooden batten. Hack off the plaster, attach the batten securely, then mount the brackets.
7 Connect the plumbing
Fit the waste outlet using a washer or putty to make a watertight seal. Tighten the back nut. Connect the trap to the waste outlet and to the end of the pipe. Run flexible 15mm (3/4in) copper or plastic pipes to the taps and join with tap connectors. Make a compression or capillary joint to join to the supply pipes.
Once a new washbasin is installed, test the plumbing for leaks. Turn on the water and check the taps, pipes and joints. Drain the system to repair any weeping joints.
Professional plumbers use a special cranked spanner rather than a standard wrench to loosen the fixing nuts of tap connectors and the back-nuts clamping the taps to the basin. These spanners are designed so they fit into the cramped space under a bath or basin and can be hired.