Bromley Water Hardness: What 280 mg/l Does to Your Home

Bromley’s tap water is hard: the Thames Water supply zone that covers Bromley town, Bickley, Shortlands, Hayes, Keston, Plaistow, Sundridge and Bromley Common averaged about 280 mg/l of calcium carbonate in 2024, with samples between 261 and 296. Yes, that is enough to scale up a hot water cylinder over a few years, and the immersion element is usually the first thing to suffer. Keeping stored hot water at about 60 degrees, descaling the small parts and, if you want to go further, fitting a softener with a separate unsoftened drinking tap are the steps that make a real difference.

How hard is Bromley water, exactly?

Thames Water grades hardness on its own scale, in milligrams of calcium carbonate per litre:

• Soft: up to 100
• Slightly hard: 100 to 150
• Moderately hard: 150 to 200
• Hard: 200 to 300
• Very hard: over 300

The Bromley Town zone sits at about 280, so it is firmly “hard”, near the top of the band. Thames Water says all the water in its region is hard, so nobody in BR1 or BR2 is getting soft water whatever their street. The figures above come from Watergrade, which republishes Thames Water’s zone data, so treat them as a guide and confirm your own postcode on Thames Water’s water quality page.

For comparison, the Sidcup zone, which also covers Chislehurst, averages about 331 and counts as very hard. Beckenham is about 290, Orpington about 291. Bromley is not the worst in the patch, but it is not far behind.

Why so hard? The supply comes off chalk. A 1919 report from Bromley’s Medical Officer of Health already described the water from the deep chalk wells as “very hard”, so this is not a new problem and it is not going away.

Where scale does the damage first

Scale forms fastest where water is heated and where it is forced through small gaps. In a Bromley house that means:

• The immersion element. It sits in the hottest water in the house. Scale builds on it like a jacket, the element runs hotter to get the heat through, and in the end it burns out. Before it fails you often hear it: a hiss, a crackle or a rumble when it is heating.
• The cylinder coil. In a cylinder heated by a boiler, the coil inside does the work. Scaled up, it passes less heat, so the cylinder takes longer to recover after a bath and you run out of hot water sooner.
• Tap washers and ceramic cartridges. Scale scores the sealing faces, so the tap drips even when it is shut hard.
• Shower valves and heads. Thermostatic valves stiffen, and the spray plate clogs so the shower comes out in a few hard jets.
• Toilet fill valves. Scale stops the valve shutting fully, so the cistern runs on into the overflow.

The Victorian villas off Widmore Road and the big Sundridge Park and Bickley houses often have large old cylinders that have been heating this water for decades. The newer flats around Bromley South usually have unvented cylinders, which scale in the same way but should only be worked on by someone qualified for unvented systems.

Signs your cylinder is scaling up

• Hot water takes noticeably longer to come back after a bath or shower.
• The immersion “kettles”: a hissing or rumbling sound while it heats.
• You run out of hot water halfway through what used to be a normal morning.
• White grit or flakes come out of the hot tap.
• The immersion trips the electrics, or the hot water is only lukewarm.

None of these means the cylinder is finished. A new element and a clean-out of loose scale at the bottom is often all it needs. A cylinder that is weeping at its seams or has a green crust at the joints is a different matter and should be looked at soon.

What actually helps

Here is the order we would suggest, cheapest first.

1. Check the cylinder thermostat. Thames Water suggests keeping stored hot water at about 60 degrees. Much hotter and scale forms faster; much cooler is not safe for stored water.
2. Descale shower heads and tap aerators every few months. Unscrew them and soak in a descaler or white vinegar, then rinse.
3. Fix drips as soon as they start. A dripping hot tap wastes heated water and the scale gets worse around the leak.
4. Have the immersion element replaced with a long-life type when it next fails, rather than the cheapest one in the box.
5. Consider a scale inhibitor on the cold feed to the cylinder or boiler. It is cheaper than a softener and protects the hot side.
6. If you want soft water through the whole house, fit a softener. Thames Water’s advice is to keep a separate unsoftened tap for drinking water, usually at the kitchen sink.

A softener needs space, usually under the sink or in a garage, a drain connection and regular salt. It is worth it in a big house with several bathrooms; in a one-bed flat a scale inhibitor and good habits may be enough.

Is hard water bad for you?

No. Thames Water’s guidance is about your plumbing and appliances, not your health. The point about the separate drinking tap is about softened water, not hard water.

When to call a plumber

Call us if:

• the immersion is not heating at all, or keeps tripping the electrics;
• the cylinder is leaking, or there is water on the airing cupboard floor;
• a tap drips even with a new washer or cartridge;
• the toilet runs on into the overflow and the small valve on the feed will not stop it.

If your hot water comes from a combination boiler or the boiler itself has stopped, that is a job for a Gas Safe registered engineer. We do not work on gas appliances. If you ever smell gas, leave the house and call National Gas Emergency on 0800 111 999 first.

We cover immersion heater and cylinder repairs in Bromley and leaking taps in Bromley. For the same problem a little further west, read our guide to immersion heaters failing in Beckenham’s hard water. More on the town itself is on our Bromley area page.

Need a plumber now?

Call 07868 281022 and tell us your postcode, what is leaking or not heating, and whether the water or the immersion is switched off. We agree the price with you before any work starts.