How to fit a kitchen sink
All the steps you need to install your kitchen sink
When replacing your kitchen sink, you’ll normally be able to use your existing water supply pipes and waste outlet. Try to choose a waste that’s similar in size to the one you’ve taken out to make fitting a lot easier.
If you’re just replacing the sink, you’ll need to choose a sink with similar shape and dimensions as your existing one. You can go larger if you have the space above and below to cut the larger opening. Measure carefully under the sink to identify the size.
It’s also easier to choose a bowl with the same depth, or close to your existing sink so you don’t have to make any significant changes to the pipework.
You may need to extend hot and cold water supply pipes where tap positions alter. Connect them to the inlet pipes of the new taps – flexible hoses are best for this. You might also have to extend the existing waste outlet pipes, to meet the trap of the new sink before you install it.
Flexible push-fit tap connectors are pretty simple to fit. Some have built-in isolating valves that mean you can change a washer without turning off your whole water supply.
Start by assembling as much of the new sink and taps as you can before you remove your old sink. Fit the waste outlet and overflow following the instructions provided. Make sure the seals provided are applied correctly to ensure the joints are leak-free.
Most sinks are held in position with supplied fixing clips. These need to be attached to the new sink before it’s fitted into the worktop spaced at intervals according to the sink instructions.
If you’re installing new taps too, assemble them according to the manufacturer’s instructions. Before you mount the tap to the sink you’ll need to attach the connection hoses, these carry light O ring seals and typically must only be hand tightened, but check in the assembly guide supplied.
Make sure the space beneath the sink is clear so you have good access.
Turn off the hot and cold water supply. The hot and cold pipes under the sink supplying the taps may have ¼ turn isolating valves, simply shut the water off by turning the screw head or handle on the valve until it’s at a right angle to the flow of the pipe. A parallel position means it’s on. If your sink doesn’t have isolating valves now’s the ideal time to fit them.
You can obtain flexible hoses with these valve types fitted. Make sure you get the right type for your tap.
If there are no isolator valves you’ll need to turn off the cold water at the mains stopcock where the water enters the house or maybe outside. There may also be a stopcock in the hot water system. Close stopcocks fully by turning the handle clockwise. A stopcock can be hard to turn as it’s not used regularly. If yours is difficult don’t use excess force. Ask an in-store advisor or plumber for advice. Check the water is off by turning on the kitchen taps. Any left-over water will drain out. If there’s still consistent flow then either you’ve not turned off the right stopcock, or the correct stopcock is faulty.
Next we’re removing the waste connection. Have a good size bowl or bucket to collect any left-over water emerging from the loose connections.
Unscrew the plastic pipe connections by hand and remove the pipework joining the waste assembly to leave it clear. It might be worth taking a picture before you disassemble the pipes so you can refer back to it when fitting back together. Place the removed pipes to one side.
Whether you’re replacing the taps or will be keeping the old ones, you’ll need to remove the taps for the time being. For hose connection types disconnect the hot and cold hose nuts at the mains pipes. Use two adjustable wrenches – one to hold the pipe connector, the other to loosen the hose nut. For directly connected pipes, unscrew the connecting nut from the tap thread.
Taps are either connected to sinks with large retaining nuts directly, or small retaining nuts on stud assemblies in combination with either standard round or horse-shoe washers with plastic spacers and rubber sealing gaskets. Take pictures as you work so you can refer to the assembly steps. Remove retaining nuts with a suitable basin or open-ended spanner and remove the taps from above and place to one side.
Next, you’ll need to loosen the clips that hold the sink in place. The clips are right up under the worktop so it’s usually easier to lie on your back so you can see the clips as you’re
loosening them. If you do this, wear eye protection to stop anything accidentally falling into your eyes. A head torch also helps.
Depending on how your sink was installed, you may have to carefully cut through the sealant with a craft knife, taking care not to damage your work surface. Wear gloves and get somebody to help you lift the sink from the worktop.
Clean off any sealant left on the worktop and clean the worktop with a suitable kitchen cleaner.
If you need to enlarge, or alter the cut-out in your worktop, you can do this with a jigsaw that’s fitted with a down-cut wood blade in order to prevent the worktop from chipping. Cover any open pipework before you start using a jigsaw. If the worktop you’re cutting is made of chipboard, you’ll need to seal all the exposed edges with a silicone or similar waterproof sealant to avoid water damage.
Wearing gloves, test fit the new sink in the cut-out and check if the waste pipes line up sufficiently. If they don’t, you’ll either need to cut it shorter or buy a longer replacement.
It’s easier to fit the taps after the sink is installed. When you’re happy that the sink fits you can go ahead and install it into the worktop. The sink manufacturer will normally provide a sealing strip for installing between the worktop and the edge of the sink to prevent water running between the two. If no seal is provided you can use silicone sealant or non-setting compound such as plumber’s putty. If you use silicone sealant, don’t use too much, as it can be difficult to clean off any extra.
Once the sink is in position, the next stage is to tighten the sink retaining clips. Like the removal process, it’s usually easier to do this lying on your back so you’re able to see the clips as you work – again a head torch is helpful and don’t forget to wear eye protection.
Fit the taps to the new sink. If you’re installing new taps, fit in accordance to the installation instructions provided. Re-fitting the originals is a reversal of the disassembly, refer to your images as a reminder. Connect the tap hoses to the mains pipework.
With the taps turned off and the bucket under the open waste on the water supply and test for leaks before the waste pipework is reinstalled – it’s easier to fix any leaks while there’s more room to work. Before turning the water back on, check that all the joints are tight. Start with the cold and only open the stopcock or isolation valve a little to begin with and then check for leaks.
If there’s a leak, make a note of where it is and turn the water off. If a compression joint is leaking, you might need to undo the joint and wrap some PTFE around the olive. Don’t be tempted to overtighten the joint as this will compress the olive too much and the leak will get worse. If the pipework is leaking, then you may need to replace it and it’s likely you’ll have to call in a plumber.
Once you’re happy there are no leaks, you can start to re-fit the waste pipework. Make sure all seals are in good condition and correctly positioned, if in doubt get new seals. It’s also worthwhile spending a few minutes cleaning the U-bend and any pipes. Re-fit the waste pipework.
With the water turned on open the taps and check for any leaks. Apply the waste plugs. Fill the sink and then releasing the water to apply maximum waste pressure.
The tap will probably gurgle the first time you use it as there’ll be air in the system. Flow will quickly revert to usual. Turn each side of the tap on slowly to prevent being splashed.
If you find a leak in the waste pipework, undo each connection and check that the seal isn’t damaged or out of place before tightening the joint back up. Take care not to overtighten the plastic thread.