PLUMBING

Replace a bar mixer shower

Swap your old bar mixer shower for a new one, checking pipework, wall type and fixings, then sealing it watertight.

BM-01Turn off the water and protect the areaTurn off the water supply to the shower using its isolation valves, or at the stopcock if there aren't any. Run the taps to clear the pipes of standing water. Lay towels or a dust sheet in the bath or shower tray to catch drips, screws and old sealant.
1 each · Old towels or dust sheet
1 each · Bucket
BM-02Remove the old bar mixerUndo the fixing screws holding the mixer body and lift it away from the wall. Loosen the pipe connections with an adjustable spanner and let any trapped water drain into your bucket. Note whether the exposed pipes are copper, plastic or old lead, as this affects the fittings you'll need.
2 each · Adjustable spanner
BM-03Check the pipework and connectionsMeasure the gap between the hot and cold pipe centres and compare it to your new mixer — most UK bar mixers use 150mm centres, but check the box. Clean up old pipe ends with wire wool if you're reusing compression fittings. Sort out any damaged or wrongly spaced pipework now, before fitting the new mixer.
1 pack · Wire wool
1 each · Tape measure
BM-04Work out what's behind the wallSolid brick or block feels solid all over when tapped, and drilling brings out brick or block dust. A stud wall sounds hollow between the uprights; run a stud detector or a strong magnet across the surface, and a line of screw heads roughly 400mm or 600mm apart shows where the studs sit. A small pilot hole tells you the rest — timber dust means a wood stud, fine grey swarf means a metal stud. Dot-and-dab plasterboard is bonded onto masonry with adhesive blobs, so it sounds part-hollow and gives slightly under thumb pressure. Lath and plaster is an older wall of thin wood strips under lime plaster — it feels a little springy and often has fine cracks.
1 each · Stud detector
1 each · Strong magnet
BM-05Mark, drill and fix the mounting pointsCables and pipes can run almost anywhere in a wall, so use a cable and pipe detector and still treat the wall as live until proven otherwise — detectors miss deep cables, cables in metal conduit, and anything hidden behind metal-backed plasterboard or a metal stud frame. Find your stopcock (usually under the kitchen sink) and check it turns freely before you start. If in any doubt, isolate the electrics at the consumer unit before drilling, and make sure the water is off at the stopcock before cutting into anything that could carry water. For solid brick or block, drill with a 7mm masonry bit to 45mm deep and use a wall plug with a 40mm screw. For plasterboard on timber studs, drill a pilot hole and drive a wood screw straight into the centre of the stud, not into the plasterboard alone. For plasterboard on metal studs, use a self-drilling metal-stud fixing or a toggle-type hollow-wall anchor — never a plain wall plug or wood screw, which strips straight through 0.5mm steel. For dot-and-dab plasterboard, use a fixing long enough (typically 60-75mm) to pass through the board and adhesive blobs and bite into the masonry behind. For lath and plaster, fix through into the timber stud or joist wherever you can, as fixing into the laths alone risks cracking the plaster. A bar mixer gets pulled and twisted every time the taps are used, so a plasterboard toggle alone often isn't strong enough — fix into a stud, a timber noggin fitted between studs, or through to the masonry behind wherever possible.
1 each · Cable and pipe detector
1 each · Masonry drill bit 7mm
1 each · Wood drill bit
4 each · Wall plugs
4 each · Screws 40mm
4 each · Self-drilling metal-stud fixings
4 each · Toggle-type hollow-wall anchors
1 length · Timber noggin (if needed)
BM-06Fit the mounting plate and bar mixer bodyHold the mixer's backplate against the wall and check it's level before marking the final fixing points. Screw the backplate on using the fixings suited to your wall type from the previous step. Fit the mixer body to the plate following the manufacturer's instructions, and don't overtighten plastic-bodied mixers, as they can crack.
1 each · Spirit level
1 each · Bar mixer shower kit
BM-07Connect the pipeworkWrap PTFE tape clockwise around any threaded tails. Connect the hot and cold pipes to the mixer using compression or push-fit fittings, matching hot to hot and cold to cold. Hand-tighten first, then nip up with a spanner — overtightening a compression joint can crack the olive.
1 roll · PTFE tape
2 each · Compression fittings
BM-08Seal around the mixer plateRun a thin, even bead of silicone sealant around the edge of the backplate where it meets the tiles, to stop water getting behind the wall. Smooth it with a wet finger or a sealant tool for a neat finish. Leave it to cure fully, usually around 24 hours, before running the shower.
1 tube · Silicone sealant
1 each · Sealant gun
BM-09Turn the water back on and testTurn the isolation valves or stopcock back on slowly and check every joint for leaks with dry kitchen roll. Run the shower on hot and cold for a few minutes, checking the temperature and pressure feel right. Check again after 24 hours, as small leaks sometimes only show once the sealant has fully cured.
1 roll · Kitchen roll
BM-10Tidy upWipe down the shower and surrounding tiles. Dispose of the old mixer and packaging responsibly, checking with your local council if it needs to go to a recycling centre rather than general waste. Put your tools away and give the area one last check for leaks.
1 each · Cloth
1 each · Bin bag

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