Water hardness

SW15 London

Harder than the UK average. Expect visible limescale on kettles and taps.

At 298 ppm, London sits among the UK's hardest water areas — compare it against the softest areas.

Hard 298 ppm London Thames Water
Your reading
298
parts per million
Soft
Moderate
Hard
Very hard
0100200300400+

What this means for your home

Based on 298 ppm in London (hard water).

  • Significant limescale buildup in kettles, pipes and boilers
  • Soap scum on shower screens and taps
  • Higher energy bills from scale in heating elements
  • Dry skin and dull hair after washing
  • White residue on dishes and glassware
Heat loss
8%
Moderate scaling
Softener salt
£17–29
per year
Worth it?
Yes
at 298 ppm
Suggested for hard water
Whole-house water softener
Best long-term protection for boilers and pipes.
From £600 installed
Shower head filter
A simple first step for limescale on tiles and glass.
From £25
Filter jug or under-sink
Improves taste and reduces kettle scale.
From £20
Softening

Should you soften the water in London?

A verdict and running-cost estimate based on SW15's 298 ppm reading, for a typical 4-person household.

Softener recommended

Water is hard to very hard, so appliance, scale and soap savings typically pay back a softener within a few years.

Recommended size
24k
grain capacity, regenerates ~every 9 days
Salt running cost
£17–29
per year (~61 kg salt)
Limescale
8%
est. heater efficiency loss. Moderate scaling
Soap saving
Moderate
Noticeable saving: soaps lather more easily, cutting detergent use.

Appliance impact at 298 ppm: noticeable: boiler/dishwasher life cut without descaling. Sized for a 4-person home; regenerates roughly every 9 days (estimate). Figures are conservative estimates and vary with household size and usage.

Water quality details

Hardness data for SW15

Sourced from Thames Water's published water-quality reports and public records.

Hardness measurements

Parts per million (ppm CaCO₃)298
Degrees Clark (°Clark)20.9
Degrees French (°fH)29.8
Degrees German (°dH)16.7
Calcium (mg/L Ca²⁺)119

Supplier and area

Water supplier Thames Water
Region London
County Greater London
Hardness band Hard
UK average 207 ppm
Visit Thames Water page
Official source
Thames Water Utilities Ltd water-hardness report

Read the hardness categories table to see where your supply falls; most of the region is hard to very hard at over 200 mg/l CaCO3.

Nearby

Other areas near London

SW14
London
297ppm
Hard
SW16
London
299ppm
Hard
SW17
London
300ppm
Hard
FAQ

Common questions about SW15

What is the water hardness in SW15 London?
The water in SW15 London has a hardness level of 298 ppm (parts per million) calcium carbonate, classified as hard. This is 91 ppm above the UK national average of 207 ppm.
Which water company supplies SW15?
SW15 London is supplied by Thames Water. Thames Water serves the London region.
Is the water in SW15 safe to drink?
Yes. Hard water at 298 ppm is safe to drink. Water hardness affects taste and can cause limescale, but it is not a health risk. In fact, hard water contains beneficial minerals like calcium and magnesium.
How can I reduce water hardness in SW15?
For hard water at 298 ppm, a whole-house water softener is the most effective solution. You can also use a jug filter for drinking water, descaling products for appliances, and a shower filter for better skin and hair.
What does 298 ppm water hardness mean?
298 ppm means there are 298 parts per million of calcium carbonate dissolved in the water. This is equivalent to 20.9 Clark degrees, 16.7 German degrees, or 29.8 French degrees. Water above 180 ppm is generally considered hard.
What size water softener do I need in SW15?
For a typical 4-person home at 298 ppm, a 24,000 grain softener is a sensible size. It would regenerate roughly every 9 days. Larger households or higher daily use need a bigger unit. These figures are conservative estimates.
How much does it cost to run a water softener in SW15?
At 298 ppm, expect to use about 61 kg of salt a year, costing roughly £17–£29/year. Water is hard to very hard, so appliance, scale and soap savings typically pay back a softener within a few years.

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