Water hardness in Derby (East Midlands): 19.81°fH, quality index 7/10. Official UK data.
✓ Compliant with DWI standardsDerby has soft water (19.81°fH). Low limescale risk: descale appliances every 3 to 4 months as a precaution.
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. Derby's water is moderately hard at 19.81°fH.
Maintenance budget: ~£55/year
For 2 persons, water at 19.81°f deposits around 1.0 kg of limescale per year in your appliances. Estimated cost in descalers, salt and filters.
Calcium: ~32 mg per litre
Your water provides 32 mg of calcium/L, which is 3% of the recommended daily intake.
Filter jug: cartridge every 6 months
At 19.81°f, replace the cartridge every 6 months. An under-sink filter lasts 6 to 12 months.
The tap water hardness in Derby is 19.81°fH, corresponding to moderately hard water. In comparison, the England average in our dataset is 18.1°fH and the East Midlands region average is 21.05°fH.
Yes. The water in Derby meets DWI sanitary standards (Water Supply (Water Quality) Regulations 2018). The hardness of 19.81°fH affects taste and appliance maintenance, not safety. Water in Derby is supplied and monitored by Severn Trent Water.
At 19.81°fH, a water softener is optional in Derby. Regular descaling (every 1 to 3 months depending on appliance) and a pitcher filter are sufficient to limit limescale buildup.
A hardness of 19.81°fH corresponds to approximately 32 mg of calcium per litre, or 3% of the recommended daily intake. This calcium is not dangerous; hard water can even contribute to your daily calcium intake.
Water in Derby is supplied by Severn Trent Water. Data source: Severn Trent Water 2025.
Data: Severn Trent Water official zone-level hardness reports (2025). Values verified via DWI drinking water quality database.