Installing A Bath Shower Mixer

For a bath/shower mixer, the one essential tool is a bath/basin spanner, and you will probably need an adjustable spanner as well, to tighten up the tap connectors. You’ll need several tools for a shower-only mixer including drill and bits, saws and screwdriver.

Installing a bath/shower mixer is a straight-forward job, as there is no extra plumbing to do unless you have to put in a booster pump to bring the water pressure up to the required level.

Fitting the mixer is very much like install-ing any other sort of tap. It is a simple task provided the work is attempted in the right order.

installing a bath shower mixerBefore removing the old taps, close the gate-valve on the cold water feed from the cistern and drain down the small amount left in the pipe by opening the cold bath tap. Similarly, turn off the water heating and close the valve supplying the hot water cylinder.

If neither of the supply pipes has a gatevalve, drain the cold water sys-tem by tying up the ballcock in the cold water cistern and opening both bath taps. Don’t turn off the main stopcock or your kitchen tap will be without water.

A bath/shower mixer can replace existing taps if the hole separation is suitable. The feed pipes are connected in the same way with a back nut tightened onto the tap tails.

Getting at the bath taps can be awkward —there’s not much space at the end of a bath and you’ll have to remove the bath side panel to give yourself access.

Disconnect the tap connectors with an adjustable spanner and then use a bath/basin spanner to undo the backnuts holding the taps in place.’ Be careful not to damage the bath and if necessary, get someone to hold the taps so that they don’t swivel around as you loosen the nuts.

Half the nuts won’t budge, try squirting some penetrating oil on them before trying to loosen them again.

When you’ve got the old taps off, clean any dirt or old compound from around the holes and polish the ends of the supply pipes with wire wool.

Before attaching the new fitting to the bath, push on the gasket which goes between the bath and the mixer.

If you need to move the positions of the tap connectors because the shanks on the mixer are either too long or too short, cut back the supply pipes and fit suitable lengths of flex-ible copper pipe which have tap connectors at one end.

The mixer is fixed to the bath by two large backnuts — these usually need plastic washers and sometimes metal ones, too, between them and the bath. Put the plastic, washers on first, followed by the metal washer and then the nut. Tighten up the nuts with a basin spanner.

Before screwing on the tap connectors, wrap a strip of PTFE tape three times around the threads on the shanks of the mixer.

Fit the hose by simply screwing it to the top of the mixer valve — again using PTFE tape to get a watertight join.

If you have one, fit the wall bracket or sliding rail next.

Measure the optimum height for the rail — or bracket — and mark its position on the wall. Check that the rail is vertical with a spirit level. Drill clearance holes for suitable wallplugs and fix the fitting in place with chromium plated screws.

After fixing a shower over a bath, you’ll need some kind of shower curtain or screen to protect the surrounding area.


New cold water supply

First turn off the water supply to the cistern or, alternatively, tie up the ballcock. Drain the whole system by turning on the bath-room cold taps.

Near the base of the tank, mark the position of the new hole. If you haven’t got a tank cutter or hole saw, drill a series of small holes inside a 22mm circle and file the edges. ,

Before you start drilling lay a sheet of polythene on the bottom of the tank to catch any bits of metal or plastic that might get into the pipes.

The new pipe is connected to the cistern with a 22mm tank connector. Make sure that you put a nylon washer on either side of the cistern before tightening up the flanged nut.

Cut, and then fit, a 150mm length of 15mm pipe to the com-pression end of the connector.

To the other end of the short pipe, fit an isolating wheel valve — again a compression fitting —and from this run 15mm piping to the cold inlet of the mixer.

Tee-ing into an existing pipe After draining down the system, mark on the pipe where you want to put the fitting — remem-ber that this should be closer to the hot cylinder or cold cistern than any other branches.

The gap you need to cut in the pipe to take a tee fitting is some-what less than the length of the tee — to allow for the length of the pipe that slots inside.

Mark the gap on the pipe with a pencil and cut.

Insert the 22mm x 22mm X 15mm reducing tee into the gap and tighten up the securing nuts on each end of the tee.

Connect the 15mm pipe to the reducing tee and run this to the appropriate inlet on the mixer.


The main problem with fitting a shower-only mixer is to decide what to do with the pipe-work immediately around the mixer. The important thing to remember is that all the fittings should be accessible in case they develop a fault.

Before doing anything, have a good look at your wall. Stud walls can be identified simply by tapping them with the handle of a screw-driver and listening for a hollow sound. If you’ve got a brick wall it will just sound ‘solid’.

Surface mounted mixers have elbows to connect them to supply pipes which go straight through the wall. If the wall is solid brick or block, this means running the pipes right through the wall (only if it’s an internal wall) or chasing a channel in the wall to take the pipes. If the wall isn’t tiled, chasing into the wall won’t be too difficult as the thickness of the pipe won’t be much more than the depth of the plaster.

Running the pipes through the wall means that you will have to conceal them on the other side — either by burying them in the plaster or by boxing them in.

With stud walls, you may be able to cut out and remove a section of plasterboard so that the pipes can run up the cavity.

With concealed mixers, the problem is exaggerated as all the connections are hidden in the wall — including the mixer valve itself and the pipe to the shower rose. So that you don’t have to make a large hole in the wall for the valve, the answer is to build a false wall and hide all the pipework between this and the real wall,

Compared with the problem of hiding the pipework, the actual fitting of a shower-only mixer is not that difficult.

Decide on the level for the shower mixer and draw a horizontal line against a spirit level. Using the mixer itself as a template, mark off and then drill 20mm holes in the wall for the supply pipes.

With solid walls, drill holes to admit the supply pipes. With a fixed rose, it ‘s neater to recess the rose pipework and mixer valve

Midway between the two holes for the supply pipes, offer up the backplate and mark the position of the screw holes. Drill out the holes in the wall and then plug and screw the plate in place.

Secure the mixer to the backplate either by screwing it on or by twisting the bayonet fixing. Fit the shower outlet adaptor to the mixer, not forgetting to include the gasket provided.

Mark a vertical line on the wall for the slide bar — the line should be about 150mm to one side of the mixer itself. Position the slide bar on the line, adjust the height and then mark, drill, and plug screw holes. Slide the shower handset onto the bar before screwing the bar to the wall.

Connect the shower hose to the mixer with the compression fitting provided after winding some PTFE tape clockwise around the threads.

When putting in a new shower-only mixer, it’s best to run a new 15mm cold supply pipe from the cold water cistern — unless you’re fitting a thermostatic type. If you do take the supply from the existing cold water pipe, make sure that you fit the tee before any other junctions. The hot supply can be taken from the existing pipe, but again, it’s best to have it as the first tee off the pipe. See Connecting to the supply.


All shower pumps must be mounted on a firm flat surface, connected to the water pipes and wired up to the mains electricity supply via a fused connection unit with a double pole switch.

There are two basic designs of booster pumps — one sort fits between the mixer valve and the shower head (spray booster), the other is installed before the mixer valve to boost the hot and cold water supplies (hot and cold pump).

Fitting a spray booster

First check that the pump has a watertight plastic cover — if it has, it can be mounted directly above the mixer valve; if it hasn’t you’ll have to position it outside the shower area.

Whichever the case, locate the pump on the wall and mark the positions of the screw holes which can then be drilled and plugged.

Decide where you are going to locate the fused connection unit which must be out of reach while you are actually using the shower. In practice it often makes sense to feed the 2.5mm twin core and earth cable through a hole drilled in the wall directly behind the pump and to mount the connec-tion unit in the next door room. Otherwise, you will have to channel the cable into the wall (surface mounted conduit is not suffi-cient) to the connection point. The supply can be taken off a spur and wired up to the fused connection unit.

Wire up the terminals at the back of the pump (following the pump manufacturer’s in-structions carefully for identification of each terminal) before making the final connections to the mains. Screw the booster pump to the wall and fix on the flexible hose to the shower valve and the shower hose to the other side of the pump.

Complete the wiring in the fused connec-tion unit and make good any damage to the plaster before clipping on the splashproof cover and using the shower.

Fitting a hot and cold pump

These pumps can be fitted to the supply pipes wherever they are conveniently close to-gether.

Mount the pump to either the wall or the floor and connect the feed pipes with the compression fittings provided — not forget ting to use a non-setting plumber’s putty to seal the joints.

The electrical connection to the pump must be made via a fused connection unit in the interests of safety.

A hot and cold booster pump is fitted at a convenient point on the supply pipework to the mixer. The power supply for the pump comes from a fused connection unit.

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