How to replace a kitchen tap: steps, tools and pitfalls

Before you buy: check the tap will suit your sink and water system

Most problems with a new kitchen tap start before it is out of the box. Check these three things first.

• Number of holes. A monobloc mixer needs one tap hole, usually around 35mm across. A two-hole or bridge mixer needs two. If you are changing type, the sink or worktop may need drilling or a blanking plate.
• Water pressure. Many modern mixers are designed for mains-pressure or combi systems and perform poorly on low-pressure gravity supplies from a tank in the loft. The product's minimum working pressure is printed in the instructions. Our guide to tap and water pressure compatibility explains how to check.
• Connections. Most modern taps come with flexible hoses that end in a 15mm fitting. If yours has old rigid copper pipes going straight into the tap, you may need adapters or new isolation valves.

A mixer tap that blends hot and cold in the body can let water pass from one supply into the other when the pressures are very different. Water regulations require the right backflow protection, often check valves supplied with the tap. Fit them if they are in the box, and ask a plumber if you are unsure.

Tools and parts you will need

Most tap replacements need only basic tools, plus something that reaches the fixing nut in the cramped space behind the sink bowl.

• An adjustable spanner, or two, so you can hold one fitting while turning another.
• A basin wrench or long tap spanner for a back nut you cannot reach by hand.
• A flat-head screwdriver to turn isolation valves.
• A bucket, old towels and a torch.
• The new tap with its hoses, seals, fixing stud and plate.
• New 15mm isolation valves if there are none, or the existing ones will not turn.

Step 1: Turn off the water

Look under the sink for small valves on the hot and cold pipes, usually with a slot that you turn a quarter turn with a screwdriver so the slot sits across the pipe. Open the tap to check that both supplies have stopped.

If there are no isolation valves, turn off the main stopcock, which is often under the kitchen sink, and on a stored hot water system also turn off the cold feed to the cylinder or the boiler's hot supply. Then open taps elsewhere in the house to drain the pipes. If the stopcock is stiff, do not force it. Our guide on finding and labelling isolation valves covers what to do.

Step 2: Remove the old tap

Take a photo of the connections before you undo anything, so you know which pipe is hot and which is cold. Hot is normally on the left as you face the sink.

• Put a towel and bucket under the connections, as some water will always come out.
• Undo the flexible hoses from the isolation valves, or the tap connectors from the supply pipes, holding the valve steady with a second spanner so you do not twist the pipework.
• Undo the back nut or fixing stud nut under the sink. This is often the fiddly part. A basin wrench helps, and a little penetrating oil left for a few minutes will free a corroded nut.
• Lift the tap out from above and clean the sink or worktop around the hole, removing old sealant and limescale so the new seal sits flat.

Step 3: Fit the new tap

Keep the hoses free of kinks and sharp bends. A flexible hose that has to be forced into a tight curve is a common source of later leaks.

• Screw the flexible hoses into the base of the new tap by hand until they are snug. Some makers allow a gentle final nip with a spanner; do not overtighten, or you can damage the thread or the rubber seal.
• Fit the rubber or foam gasket that goes between the tap and the sink, then feed the hoses and fixing stud through the tap hole.
• From underneath, fit the horseshoe plate or washer and tighten the fixing nut while someone holds the tap straight from above. Firm is enough. The tap should not move when you push the spout.
• Connect the hoses to the isolation valves, hot to hot and cold to cold. Hand-tighten, then use a spanner for about another quarter to half turn while holding the valve steady. Fibre and rubber washers do not need PTFE tape on their sealing faces.

Step 4: Turn the water on and check for leaks

Unscrew the aerator on the end of the spout if you can, so any debris from the pipes does not block it. Turn the isolation valves or stopcock back on slowly, then run the tap on hot and cold for a minute to flush it through and clear air.

Dry every joint with a paper towel and check again after ten minutes and an hour. A slow weep often only shows up later. If a joint drips, turn the water off and tighten it slightly. If it still drips, undo it and check the seal is seated properly rather than tightening harder.

If you hear banging when the new tap closes, see our guide on water hammer after a tap replacement.

Common problems and when to call a plumber

Plenty of people change a kitchen tap themselves without trouble. These are the situations where the job stops being a simple swap.

Repair the old tap or replace it?

If the old tap is only dripping from the spout, the fix may be a new cartridge or washer rather than a new tap. Our guides on fixing a dripping tap and on replacing a cartridge or the whole tap help you decide. Leaks around the base or the swivel spout have their own causes, covered in our guides on a kitchen tap that is loose at the base and one leaking at the swivel.

Getting a plumber to do it

If you would rather not, or the old tap will not come out, Loyal Plumbers fits and replaces kitchen taps across London and everywhere inside the M25, and can fit isolation valves at the same visit so the next job is easier. We run 10 vans, 24 hours a day, and our call-out charge is £60.

When you get in touch, tell us the type of tap you are fitting, whether you have already bought it, whether there are isolation valves under the sink, and whether your hot water comes from a combi boiler or a cylinder.