How to descale a shower head in a hard water area

Why shower heads block up in London

Thames Water says all the water it supplies is hard, because it passes through chalk and limestone before it reaches the treatment works. Hard water carries dissolved calcium and magnesium, and when it is heated some of that comes out as limescale.

Shower heads suffer more than most fittings because warm water sits in them between uses and dries on the face. The small nozzles narrow, the spray goes uneven or sideways, and eventually some jets stop altogether. The water pressure reaching the head has not changed, but less of it gets out.

Electric showers make it worse, because the water is heated inside the unit just before it reaches the head. A badly scaled head also holds back the flow through the heater, which on some models makes the water run hotter or the shower cut out, so shower makers advise keeping the spray plate clean.

What you need

You do not need anything specialist.

• White vinegar, or a descaler that says it is suitable for shower heads
• A bowl or jug deep enough to cover the face of the head
• A plastic food bag and an elastic band or cable tie, if the head is fixed
• An old toothbrush and a cloth
• A soft cloth to protect the finish if you need grips to undo a tight fitting
• Rubber gloves if you are using a chemical descaler

Step by step: a head that unscrews

Most handheld shower heads and many fixed ones unscrew from the hose or arm by hand. Turn the head anticlockwise at the knurled nut where it joins the hose. There is a small rubber washer inside the connection, and sometimes a filter screen, so put them somewhere safe.

• Turn the shower off. On an electric shower, switch it off at the isolator as well before handling the head.
• Unscrew the head and rinse off any loose dirt.
• Many heads have a face plate that twists or unclips off. If yours does, take it off so the solution reaches the inside.
• Soak the head in vinegar or descaler. About 30 minutes to an hour is enough for light scale. Heavily scaled heads can be left longer in vinegar, but follow the time on a chemical descaler.
• Rub each rubber nozzle with your thumb or the toothbrush. The scale inside should crumble and wash out.
• Rinse well in clean water and run the shower for a minute before refitting, to flush out anything loose from the hose.
• Check the washer is in place and refit the head hand tight. Overtightening splits washers and plastic threads.

Step by step: a fixed or rainfall head

Ceiling-mounted and large rainfall heads are often awkward to remove, and a few are not designed to come off at all. Fill a strong plastic bag with enough vinegar to cover the face, lift it up around the head and fasten it round the arm with an elastic band or cable tie. Leave it for an hour, take it off, rub the nozzles and run the shower to rinse it through.

If you do unscrew a fixed arm or head, hold the arm steady at the wall with your other hand. Twisting the arm can loosen the fitting behind the tiles, and a slow leak there shows up weeks later as a stain on a ceiling or a damp patch on the other side of the wall.

Finishes that need care

Vinegar is mildly acidic. It is fine on standard chrome and plastic heads, but brushed, black, gold, bronze and brass finishes can be marked or dulled by acid descalers. Check the manufacturer's care guide before soaking one of these, and if in doubt use warm soapy water and rub the nozzles rather than soaking. Never use abrasive powders, scouring pads or bleach on a shower head. They damage the finish and can perish the rubber nozzles.

How often to descale

In a hard water area, every one to three months keeps most shower heads flowing well. Heads with soft rubber nozzles that you rub clean after each shower can go longer. A shower that is rarely used, such as in a spare room, needs it less for scale but should be run through regularly for hygiene.

Landlords and businesses have a specific reason to keep to a schedule. The Health and Safety Executive's legionella guidance says shower heads should be dismantled, cleaned and descaled quarterly, or as often as the risk assessment requires, because scale and sediment in the head give bacteria somewhere to grow. Our guide to legionella risk assessment for landlords explains how this fits into the wider duty.

Still a weak shower after descaling?

If the head is clean and the flow is still poor, look behind it. Take the head off, point the hose into the bath and turn the shower on. If the flow from the bare hose is also weak, the head was not the problem.

Common causes are a kinked or collapsed shower hose, a blocked filter screen in the hose connection or the valve inlets, a sticking thermostatic cartridge, a failing shower pump, or low incoming pressure. Our guide to low water pressure in the shower goes through each one. If the water is also running hot and cold on its own, see the guide to thermostatic shower temperature problems, and if an electric shower cuts out or will not heat, see electric shower not working.

A water softener or scale reducer can cut how often all this is needed across the house. Whether one is worth it depends on the house and how the water is used, and our guide on whether a water softener is worth it covers the trade-offs.

Getting help

If the shower is still weak, the valve is dripping after you turn it off, or the arm has come loose at the wall, a plumber can find the cause and fix it without taking the whole bathroom apart. Loyal Plumbers repairs showers, valves, hoses and pumps across London and everywhere inside the M25, 24 hours a day, with 10 vans on the road. Our call-out charge is £60. Call 020 4652 8585 or send an enquiry with the type of shower and what the flow is doing.