How to install a kitchen sink

A new sink can give your kitchen a whole new look and it’s not as hard to fit as you may think

stainless steel sink

A new sink can totally transform the look and feel of your kitchen. In this step-by-step tutorial, we’ll explain how to fit a new over-mounted sink yourself (an under-mounted sink requires professional installation).

Before you get started, check out our guide to choosing the right sink for your kitchen, which explains what factors you need to consider before you buy, and the different sink styles on the market.

You will need

  • 4-in-1 screwdriver
  • Two 250mm adjustable spanners
  • Large pump pliers
  • Bucket or bowl
  • Rags
  • Caulk gun
  • Cordless drill
  • Head torch
  • Safety goggles
  • Work gloves
  • Hacksaw
  • Jigsaw
  • 15mm pipe cutter
  • Thin blade scraper
  • Pipe wrench
  • Plumbers tape
  • Putty knife
  • Stanley knife
  • Caulk remover
  • Silicone caulk
  • Flexible hose connectors (with isolating valves if needed)
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Step 1

Assemble as much of your new sink and taps as you can before you remove your old sink. Fit the waste outlet and overflow following the manufacturer’s instructions. Most sinks are held in place with fixing clips which need to be attached to the new sink before it’s fitted into the worktop, spaced at intervals according to the instructions.

Before you fit the tap to the sink, attach the connection hoses according to the manufacturer’s assembly guide.

Step 2

Clear the space beneath the sink, then shut off the 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.

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. There may also be a stopcock in the hot water system. Close the stopcocks fully by turning the handle in a clockwise direction. Make sure the water is off by turning on the kitchen taps.

If your sink doesn’t have isolating valves, now’s the ideal time to fit them. You can buy flexible hoses with these valve types fitted in all good DIY stores – just take care you buy the right type for your tap.

Step 3

Next you need to remove the waste connection. Have a large bowl or bucket to hand to collect any leftover 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. Put the removed pipes to one side.

Top tip: To make re-assembly easier, take a photo before you disassemble the pipes so you can refer back to it when fitting back together.

Step 4

Remove the taps. For hose connection types disconnect the hot and cold hose nuts at the mains pipes. Use two adjustable spanners – 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.

Take photos as you work so you can refer to the assembly steps. Remove retaining nuts with a suitable open-ended spanner and remove the taps from above and place to one side.

Step 5

Remove the sink, starting by loosening the clips that hold the sink in place. The clips will be right up under the worktop so it’s usually easier to lie on your back – just be sure to wear safety goggles. A head torch may come in handy, too.

Depending on how your sink was fitted, you might have to carefully cut through the sealant with a Stanley knife. Wear gloves and get somebody to help you lift the sink from the worktop, as they are usually very heavy.

Step 6

If you need to enlarge, or alter the aperture in your worktop to accommodate your new sink, do this with a jigsaw fitted with a down-cut wood blade 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 the new exposed edges with a silicone or waterproof sealant to avoid water ingress.

Test fit the new sink in the aperture and check if the waste pipe lines up sufficiently. If they don’t, you’ll either need to cut it shorter or buy a longer replacement.

 

Step 7

If you’re happy with the fit, install the sink. The manufacturer will normally provide a sealing strip to place between the worktop and the edge of the sink to prevent water running between the two. If one isn’t provided, you can use silicone sealant – but don’t use too much, as it can be difficult to clean off any extra.

Once the sink is in place, you need to tighten the sink retaining clips. Again, this is easier to do this lying on your back so you can see the clips as you work – again use a head torch and safety goggles.

Step 8

If you’re fitting new taps, install them following the manufacturer’s instructions. Re-fitting the originals is a reversal of the disassembly, so refer to the photos you took earlier as a reminder.

Connect the tap hoses to the mains pipework. Ensure that all the joints are tight, then, starting with the cold tap and only opening the stopcock or isolation valve a little to start with, check for leaks – make sure a bowl or bucket is placed beneath in case of any drops.

If a compression joint is leaking, you may need to undo the joint and wrap some PTFE around the olive. Don’t over-tighten the joint as this will compress the olive too much and cause the leak to worsen. However, if the pipework is leaking, then you might need to replace it – unless you’re confident, you’ll need a plumber for this.

Step 9

If you’re satisfied that there are no leaks, it’s time to re-fit the waste pipework. Ensure all seals are in good condition and correctly positioned – if in doubt get new seals. It’s also worth spending a few moments cleaning the U-bend and any pipes.

Re-fit the waste pipework. With the water turned on, open the taps and check again for any leaks. Apply the waste plugs and then fill the sink and then release the water to apply maximum waste pressure.

The tap might gurgle the first time you use it because there will be air in the system, but the flow should quickly go back to normal. Turn each side of the tap on slowly to prevent being splashed. If you discover a leak in the waste pipework, undo each connection and check that the seal isn’t damaged or out of place before retightening the joint, taking care not to over-tighten the plastic thread.

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Common mistakes

  • Don’t choose a sink that’s smaller than the current aperture, unless you are also planning to replace the worktop at the same time.
  • Don’t choose a sink that hangs down too low, as it won’t drain properly and may not fit correctly in the base unit. 
  • Make sure the sink aperture in the worktop is sound. Leaks around a sink rim can soak the particleboard under a laminate worktop. Severe swelling will prevent the new sink from sitting flat on the countertop, and crumbling particleboard won’t provide a solid base for the clips that fasten the sink to the worktop.
  • Use the right sealant. Plumber’s putty has long been the standard sealant for sinks, but it eventually dries out, cracks and causes leaks. Avoid drips and leaks by using a silicone sealant instead.
  • Thoroughly remove old caulk before fitting a new sink. The caulk around your new sink is all that stands between your worktop and water damage. For a lasting, watertight bond with the worktop, you have to completely remove the old caulk.
  • Working on the water pipes always shakes sediment loose. The last thing you want is for these deposits to clog your new tap. Avoid this problem by purging the lines before connecting the new supply lines.