Water hardness in Southampton (South East England): 30°fH, quality index 5/10. Official UK data.
✓ Compliant with DWI standardsSouthampton has hard water (30°fH). Weekly descaling is recommended. A water softener becomes worthwhile above 30°fH.
UK tap water is subject to the Water Supply (Water Quality) Regulations 2018, overseen by the Drinking Water Inspectorate (DWI). The sanitary compliance indicator shows whether the latest official analyses found any non-conformities on parameters such as bacteriology, nitrates, pesticides or heavy metals.
The TH (Total Hardness) measures calcium and magnesium content. Below 10°fH: soft. From 10 to 20: moderately soft. From 20 to 27: slightly hard. From 27 to 35: hard. Above 35: very hard. Southampton's water is hard at 30°fH.
Maintenance budget: ~£84/year
For 2 persons, water at 30°f deposits around 1.4 kg of limescale per year in your appliances. Estimated cost in descalers, salt and filters.
Calcium: ~48 mg per litre
Your water provides 48 mg of calcium/L, which is 5% of the recommended daily intake.
Filter jug: cartridge every 4 months
At 30°f, replace the cartridge every 4 months. An under-sink filter lasts 6 to 12 months.
The tap water hardness in Southampton is 30°fH, corresponding to hard water. In comparison, the England average in our dataset is 18.1°fH and the South East England region average is 26.9°fH.
Yes. The water in Southampton meets DWI sanitary standards (Water Supply (Water Quality) Regulations 2018). The hardness of 30°fH affects taste and appliance maintenance, not safety. Water in Southampton is supplied and monitored by Southern Water.
With 30°fH, a water softener is a worthwhile investment in Southampton. Limescale reduces the lifespan of boilers, washing machines and coffee makers and increases energy consumption by 10 to 15% per mm of scale. An anti-scale filter is a minimum at this hardness level.
A hardness of 30°fH corresponds to approximately 48 mg of calcium per litre, or 5% of the recommended daily intake. This calcium is not dangerous; hard water can even contribute to your daily calcium intake.
Water in Southampton is supplied by Southern Water. Data source: Southern Water 2025.
Data: Southern Water official zone-level hardness reports (2025). Values verified via DWI drinking water quality database.