Hard water in Reading: limescale, boilers and what helps

If you've moved to Reading from somewhere with soft water, the white crust on your kettle and shower screen will have told you already. Hard water isn't a health problem, but it does cost money over time through scaled-up appliances, shorter-lived taps and less efficient heating. Here's how hard the water is, what it does, and what you can do about it.

How hard is the water in Reading?

Thames Water supplies Reading. It says around 65 percent of its water comes from rivers and 35 percent from underground sources that pass through chalk and limestone. That's why it describes all the water in its region as hard. It can't change the hardness, because it comes from the rock the water passes through.

Thames Water uses these bands, measured in milligrams of calcium carbonate per litre (roughly the same as parts per million):

• Soft: up to 100 mg/l.
• Slightly hard: 100 to 150 mg/l.
• Moderately hard: 150 to 200 mg/l.
• Hard: 200 to 300 mg/l.
• Very hard: more than 300 mg/l.

A 2025 study reported by the local news site Reading Today measured Reading's water at 329 ppm, ninth hardest of the UK cities surveyed. That puts it in the very hard band. The exact figure can vary by area, so if you're choosing equipment, ask Thames Water for the hardness at your postcode.

Is hard water safe to drink?

Yes. Thames Water says hard water is not considered harmful, and that research suggests the minerals in it can be good for you, particularly for bones. The problems hard water causes are with your home, not your health.

What does hard water do to your home?

When hard water is heated, the minerals come out as limescale. Anything that heats water or has small openings gets the worst of it.

• Kettles and coffee machines scale up quickly and take longer to boil.
• Shower heads clog, giving weaker, uneven spray.
• Tap aerators block and taps can start to drip as scale damages the washers and cartridges.
• Washing machines and dishwashers lose efficiency as their heating elements scale.
• Hot water cylinders, immersion heaters and the heat exchangers in combi boilers can scale up, which makes them work harder.

Industry body British Water says just 1 mm of limescale can raise the energy used to heat water by 7 to 10 percent.

How to reduce limescale without a water softener

• Keep stored hot water at about 60 degrees Celsius. Hotter water creates more scale, and Thames Water suggests 60 as the setting. Don't go lower with a hot water cylinder, as stored water needs to stay hot enough to control bacteria.
• Use a scale collector in your kettle and empty the kettle if you won't use it for a while.
• Soak shower heads and tap aerators in descaler or diluted white vinegar every few months.
• Use the descaling programme on your washing machine and dishwasher, and dishwasher salt if your machine takes it.
• Ask a plumber about a scale reducer, which typically costs £30 to £200 fitted. It doesn't remove hardness but limits scale in a combi boiler or water heater.

Hard water and your boiler

A combi boiler heats water as it flows through, so limescale can build up in its heat exchanger. Signs include hot water that goes hot and cold, a kettling or rumbling noise, and the boiler cutting out. Your annual boiler service is a good time to ask whether scale is building up and whether a scale reducer or inhibitor would help. Any work on the boiler itself must be done by a Gas Safe registered engineer.

Do you need a water softener in Reading?

A water softener removes the minerals that cause scale. Price guides suggest it's worth considering once hardness is above about 200 ppm, which Reading comfortably exceeds. A softener typically costs £600 to £2,000 fitted, plus salt. Thames Water advises keeping a separate tap of unsoftened water for drinking and cooking if you fit one.

Scale reducer or water softener: which is right?

• Scale reducer: cheap and small, fitted to the pipe feeding a boiler or water heater. It protects one appliance but doesn't soften your water.
• Water softener: costs more and needs salt, but treats the water for the whole house, including showers, taps and appliances.
• Both: some homes fit a softener and keep a scale reducer on the boiler feed if the softener doesn't cover it.