SES Water water hardness
Ranges from moderately hard to hard across the supply area.
SES Water supplies water ranging from moderately hard to hard across its area, so the figure for your own postcode is worth checking.
As many of our water sources are naturally hard, we soften the water slightly as part of the water treatment process. Some supplies are naturally softer and do not require further treatment.
SES Water, on their own website, source — checked 2026-08-24
North Downs chalk, and naturally hard at source — but SES Water partially softens the supply during treatment, so what reaches the tap is less hard than the geology suggests. Still a strong softener market.
Correction, 2026-08-24: We previously showed 'very hard'. SES Water partially SOFTENS its supply during treatment, so what reaches the tap is less hard than the source. Reduced to match.
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 SES Water supplies
Regions: South East England
Counties and areas: Surrey, Kent, West Sussex, Greater London
Supply boundaries do not follow county boundaries, and several companies may supply parts of the same county. Always check your own postcode.