Swanley Hard Water (327 mg/l): Is a Softener Worth It?

Swanley’s water is very hard: the Thames Water Swanley supply zone averaged about 327 mg/l of calcium carbonate in 2024, and anything over 300 is “very hard” on Thames’s own scale. For a family home with a hot water cylinder, several showers and a dishwasher, a softener is usually worth it, because it protects taps, valves, the cylinder and appliances all at once. Thames Water’s advice is to keep a separate unsoftened tap for drinking. If a softener is more than you want to spend, keeping hot water at about 60 degrees, descaling regularly and fitting a scale inhibitor will cut the damage.

Who supplies Swanley’s water?

This catches people out. Swanley and Hextable are in Kent, and Sevenoaks District Council is the local authority. But the water does not come from South East Water, which supplies the eastern half of Sevenoaks District around Sevenoaks town and Otford. In Swanley and Hextable, Thames Water supplies the clean water and collects the sewage, according to Sevenoaks District Council’s 2026 statement of common ground with Thames Water.

So if you are looking up hardness, leaks, bills or lead pipes, Thames Water is the company to check with. Enter your postcode on its water quality page to confirm your zone.

How Swanley compares

Using Watergrade’s republished Thames zone data for 2024:

• Swanley: about 327, very hard
• Sidcup and Chislehurst: about 331, very hard
• Bexleyheath and Welling: about 359, very hard
• Orpington: about 291, hard
• Bromley town: about 280, hard

Hextable’s exact figure is not published separately, so check your postcode. The water comes off the chalk, which is why it is so hard.

What very hard water does to a Swanley home

Swanley grew mostly after the war, and a lot of its houses are 1950s and 1960s estates with sixty-year-old plumbing. Scale adds to that wear:

• Taps drip as scale scores ceramic cartridges and hardens washers.
• Toilet valves stick and run on into the overflow.
• Shower heads and valves clog, stiffen and lose temperature control.
• Cylinders and immersion elements scale up, heat slowly and fail early. “Scaled solid” is not an exaggeration in some Swanley airing cupboards.
• Washing machines, dishwashers and kettles work harder and wear out sooner.
• Combi boilers can scale up on the hot water side, which is a job for a Gas Safe registered engineer.

Is a softener worth it?

It depends on the house.

Probably yes if you have a hot water cylinder, two or more bathrooms, a household that uses a lot of hot water, or you are fed up with replacing elements, valves and cartridges.

Maybe not in a small flat with a combi boiler and one bathroom, where a scale inhibitor on the boiler feed and good habits may be enough.

What a softener needs:

• space, usually under the kitchen sink, in a utility room or in the garage;
• a connection on the incoming main, after the stopcock;
• a drain for the regeneration water;
• regular top-ups of salt;
• a separate unsoftened drinking tap, as Thames Water recommends.

It should be fitted by someone who knows the water fittings rules, ideally a WaterSafe approved plumber, so the installation includes the right valves to protect the mains supply.

Cheaper steps that help

If a softener is not for you, these make a real difference in 327 mg/l water:

• keep stored hot water at about 60 degrees, as Thames Water advises; hotter water scales faster;
• descale shower heads and tap aerators every couple of months;
• fit a scale inhibitor on the cold feed to the cylinder or combi boiler;
• fix drips as soon as they start;
• fit a long-life immersion element next time the old one fails.

Softener or scale inhibitor: what is the difference?

A softener actually removes the calcium and magnesium from the water, using a resin that it cleans with salt every few days. The water that comes out is soft, so nothing downstream scales up, and you will notice it in the shower, the kettle and on the glass screen.

A scale inhibitor does not remove the hardness. It changes how the minerals behave, usually with a small dose of a food-safe compound or with a magnetic or electrolytic unit, so less scale sticks to hot surfaces. It protects one appliance or one circuit, typically the boiler or cylinder, and needs little maintenance.

In a Swanley post-war semi with a cylinder in the airing cupboard, an inhibitor on the cylinder feed is a sensible minimum. A softener is the full answer.

Is hard water safe to drink?

Yes. Thames Water’s hardness advice is about your plumbing and appliances. The separate tap is recommended because softened water is not the best choice for drinking or for making up baby feeds.

Signs scale is already causing trouble

• A tap that drips even when shut hard.
• A toilet that keeps refilling.
• An immersion heater that hisses or trips.
• Hot water that runs out sooner than it used to.
• A shower that has gone from a spray to a few hard jets.

For more on the drips, see our guide to very hard water and dripping taps in Welling.

When to call

Call us if a tap will not stop dripping, the cylinder is leaking, the immersion has failed, or you want advice on fitting a softener. We cover leaking taps in Swanley and immersion heaters and cylinders in Swanley. More on the town, Hextable and Crockenhill is on our Swanley area page.

Need a plumber now?

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