Southern Water water hardness
Ranges from hard to very hard across the supply area.
Southern Water supplies water ranging from hard to very hard across its area, so the figure for your own postcode is worth checking.
Most of the water we supply is hard, as it comes from underground chalk aquifers with high levels of calcium.
Southern Water, on their own website, source — checked 2026-08-24
Chalk downland supply along the south coast.
What this means for your home
You have hard water — scale protection is worth having.
The World Health Organization notes that water at 200 mg/l or above will produce scale, and that is where this band begins. At this level limescale is a recurring cost rather than an occasional nuisance, and many boiler manufacturers require scale protection to keep the warranty valid. A softener is worth costing out properly.
Where Southern Water supplies
Regions: South East England
Counties and areas: Kent, Sussex, Hampshire, Isle of Wight
Supply boundaries do not follow county boundaries, and several companies may supply parts of the same county. Always check your own postcode.