Water hardness in Slough (South East England): 31.2°fH, quality index 4/10. Official UK data.
✓ Compliant with DWI standardsSlough has hard water (31.2°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. Slough's water is very hard at 31.2°fH.
Maintenance budget: ~£87/year
For 2 persons, water at 31.2°f deposits around 1.5 kg of limescale per year in your appliances. Estimated cost in descalers, salt and filters.
Calcium: ~50 mg per litre
Your water provides 50 mg of calcium/L, which is 5% of the recommended daily intake.
Filter jug: cartridge every 4 months
At 31.2°f, replace the cartridge every 4 months. An under-sink filter lasts 6 to 12 months.
The tap water hardness in Slough is 31.2°fH, corresponding to very 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 Slough meets DWI sanitary standards (Water Supply (Water Quality) Regulations 2018). The hardness of 31.2°fH affects taste and appliance maintenance, not safety. Water in Slough is supplied and monitored by Thames Water.
With 31.2°fH, a water softener is a worthwhile investment in Slough. 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 31.2°fH corresponds to approximately 50 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 Slough is supplied by Thames Water. Data source: Thames Water 2025.
Data: Thames Water official zone-level hardness reports (2025). Values verified via DWI drinking water quality database.