Replacing A Sink

This how to gives advice on replacing a sink and tap set. There are several different sizes and fittings available for modern taps, but the basic technique is the same.

You may have isolator valves fitted to the hot and cold supply pipes underneath the sink, which means you can turn off the water to just the sink and not the entire system. If you don’t have these valves, here’s how to turn off the hot and cold water. It’s always worth fitting isolator valves when you are replacing the taps and/or sink. The valves only cost a few pounds each and make repairs in the future much simpler.


How to Turn Off the Cold Water
If there are no isolator valves fitted under the sink, turn off the main stopcock, a brass tap fitted on the pipework, that’s usually in the kitchen or wherever your mains water enters the house. This will stop the flow of cold water. Turn on the cold taps on the sink until the water stops running. If you can’t find the stopcock, turn off the water authority’s valve under the cover in the street or front garden. You’ll need a special long-handled spanner, available from plumbers’ merchants.


How to Turn Off the Hot Water
Always turn off the boiler and immersion heater before draining the hot water. Turn off the valve on the cold feed pipe to your storage tank and run the hot taps to get rid of water in the pipes. If you can’t find this valve, tie the ball valve in the loft storage header tank to a piece of wood laid across the tank top. Turn on all the cold taps in the bathroom to empty the tank. When no more water comes out, run the hot taps until these run dry as well.


Fitting a new sink

If you don’t have hot and cold isolator valves directly under the sink, now’s the time to fit them so that you can turn off the supply just to one tap, not the whole house, if you need to replace a washer in the future. These valves come with screw-on compression joints that are fixed to the end of the copper pipe with a pair of adjustable spanners. You can also buy versions to use with plastic piping.


    1. 1. If your new sink isn’t exactly the same size as the old one, you’ll need to use a jigsaw to enlarge the cut-out on the worktop. Use the template provided with the sink or the sink itself to mark the area to be cut out. Remember not to cut around the edge of the sink itself or it will drop through the hole – follow the manufacturer’s instructions to allow the rim to sit on the top surface of the worktop.


    1. 2. Make sure there are no obstructions or wires/pipes directly under the cutting line. Mark the positions of the taps and waste pipes on the top and the cupboard carcass underneath. Cut out the sink recess and any cut-outs in the cabinet needed for the taps and waste pipes.


    1. 3. You may be able to connect the water supply pipes and waste directly to the new sink taps and waste trap. If not, use longer flexible tap connectors and waste pipeparts to make the connections. It’s often easiest to screw the new tap connectors to the tap and the new waste trap to the sink before fitting the sink. Always use the washers and gaskets supplied to give a watertight seal around the new taps. Lay your sink upside-down on a towel to prevent scratching as you work.


  1. 4. Connect the overflow to the waste pipe with the parts supplied. Place the sink into the worktop and double check all the pipes can be easily connected. Remove the sink and follow the manufacturer’s instructions for sealing around the lip of the unit. This will be either a mastic or flexible foam tape. Fit the sink and tighten all the plumbing connections using adjustable spanners.


It’s essential that any changes you make to your plumbing system maintain effective earth bonding. Adding new sections of plastic pipe may break this bonding. Never remove the earth wire straps from the pipes under the sink. If you’re unsure, always call in a certified electrician to check the bonding.