Replace a bath mixer tap

Swap your old bath mixer tap for a new one safely, covering both deck-mounted and wall-mounted fittings.

BM-01Isolate the water supplyFind your stopcock, usually under the kitchen sink, and turn it clockwise to shut off the water. Open the bath taps to check the flow stops, then leave them open to drain the remaining water from the pipes. If your bath has separate isolation valves under the panel, close those too - it makes the rest of the job much easier.

BM-02Remove the bath panel and drain the pipeworkUndo the screws or clips holding the bath panel and lift it away to reach the pipework underneath. Lay an old towel down and put a bucket under the tap connections to catch any drips. Loosen the tap connectors slightly to let any trapped water run out before you disconnect anything fully.

1 each · Bucket

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1 each · Old towel or rag

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BM-03Disconnect and remove the old tapUse an adjustable spanner or basin wrench to undo the flexible tap connectors from the old tap tails, turning anti-clockwise. Support the tap from above so it doesn't drop into the bath as it comes free. Undo the backnuts holding the tap to the bath deck or wall bracket, then lift the old tap away.

1 each · Basin wrench

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1 each · Adjustable spanner

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BM-04Clean the fitting area and check the new tapWipe away old limescale, sealant or grime from the bath deck holes or wall bracket with a cloth, so the new tap sits flush. Lay out the new tap's washers, connectors and fixing kit, and check the hole spacing matches your bath before you start fitting. Look for the WRAS approval mark on the box - this shows the fitting is legal to connect to the mains supply.

RULES

1 each · Cloth or scourer

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KNOW THE RULES

The Water Supply (Water Fittings) Regulations 1999 require any tap connected to the mains water supply to be an approved fitting (look for the WRAS mark). This applies whenever you replace or install plumbing fittings, not just new builds.

BM-05Fit a deck-mounted mixer tap (through the bath)Most bath mixers sit on the bath deck, with tails dropping through the existing holes - use this method unless your tap is wall-mounted. Fit the new rubber or foam washers onto the tap tails, push the tap through the holes from above, then thread the backnuts on from underneath. Tighten by hand first, then finish with a basin wrench until snug - don't overtighten, as this can crack the bath or distort the seal.

1 each · Bath mixer tap

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BM-06Fit a wall-mounted mixer tap (fixing into the wall)Skip this step if your mixer sits on the bath deck. If it's wall-mounted, its mounting plate or unions need to be fixed securely into the wall behind the tiles. Work out what's behind the tiles first: tap along the wall - a solid, dull sound is brick or block; a hollow sound between hits is a stud wall. Find a stud with a detector or magnet tracking screw heads, then drill a small pilot hole - timber dust means a timber stud, fine grey swarf means a metal stud. Cables and pipes can run anywhere behind a bathroom wall, and a metal stud frame confuses cheap detectors, so treat the wall as live until you've proved otherwise. Check your stopcock turns off cleanly before you drill, and isolate the circuit at the consumer unit too if there's any doubt - shower and lighting circuits often share the same wall. Fixings by wall type: solid brick or block - drill an 8mm hole 40mm deep, insert a plug, use a 50-60mm screw. Timber stud - a 50mm wood screw into the centre of the stud. Metal stud - never a plain plug or wood screw, they strip straight through 0.5mm steel; use a self-drilling metal-stud fixing or a rated hollow-wall toggle. Plasterboard between studs - a toggle fixing rated for at least 5kg, since the tap gets pulled every time it's used. Dot-and-dab - a 75-90mm fixing long enough to reach the masonry behind the dabs. Lath and plaster - find the timber stud behind with a bradawl first and fix into that, or fit a timber pattress screwed across the studs to spread the load.

4 each · Wall plugs (masonry)

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2 each · Hollow-wall toggle fixings

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2 each · Self-drilling metal-stud fixings

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1 each · Timber pattress board (for lath and plaster)

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BM-07Reconnect the pipeworkWrap PTFE tape clockwise around any threaded connections, 3-4 turns, then reconnect the flexible tap connectors to the tap tails and the existing pipework. Tighten each joint firmly with a spanner, but don't force it - overtightening can crack fittings. Double-check hot and cold are connected to the correct side before moving on.

1 roll · PTFE tape

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2 each · Flexible tap connectors (if not supplied with tap)

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BM-08Turn the water back on and check for leaksTurn the stopcock back on slowly and open any isolation valves under the bath. Check every joint you touched - tap tails, connectors and unions - for drips, using a dry piece of tissue to spot small leaks. If you find one, turn the water off again and tighten that joint a little more before retesting.

BM-09Test the tap and check the temperatureRun the hot and cold taps separately to check they work smoothly and are on the correct side - hot on the left is standard in the UK. Let the water run for a minute and check the temperature feels right and the flow is steady, with no spluttering that suggests trapped air in the pipe.

BM-10Refit the panel and tidy upOnce you're confident there are no leaks, screw or clip the bath panel back into place. Wipe down the bath and surrounding tiles, and dispose of the old tap and packaging responsibly - some recycling centres accept metal taps.

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