Water Hardness and Quality in St Helier
Supplied by Thames Water · Mitcham (SLW14)
St Helier has hard water with quality that meets all UK drinking water standards.
Check a specific postcode in St Helier
Water Quality Scorecard
Total Hardness
Guideline: 150+ mg/l is considered hard
262mg/l CaCO₃
UK Average: 197.72 mg/l CaCO₃Above Average
LowAverageHigh
pH Level
UK Standard: 6.5 – 9.5
7.7pH units
UK Average: 7.43 pH unitsWell Above Average
LowAverageHigh
Free Chlorine
Guideline: below 1 mg/l
0.63mg/l
UK Average: 0.45 mg/lWell Above Average
LowAverageHigh
Nitrate
UK Standard: max 50 mg/l
22mg/l
UK Average: 16.9 mg/lAbove Average
LowAverageHigh
Lead
UK Standard: max 10 µg/l
2.4µg/l
UK Average: 1.08 µg/lWell Above Average
LowAverageHigh
Fluoride
UK Standard: max 1.5 mg/l
0.15mg/l
UK Average: 0.19 mg/lAbove Average
LowAverageHigh
Water Hardness in St Helier
Hardness is the most searched water quality metric. It affects limescale buildup in kettles, boilers, and pipes.
262mg/l CaCO₃Hard
Soft
Mod. Soft
Slightly Hard
Mod. Hard
Hard
Very Hard
St Helier has hard water at 262 mg/l. You will likely experience significant limescale buildup in kettles, boilers, and on bathroom surfaces. Many residents in your area use water softeners or anti-limescale products.
Water Source Information
- Water Company
- Thames Water
- Supply Zone
- Mitcham (SLW14)
- Source Type
- River
- Treatment Works
- Mitcham Treatment Works
- Last Tested
- 2025-12-31
- Data Source
- Thames Water
Frequently Asked Questions
Is the water hard in St Helier?▾
Yes, St Helier has hard water at 262 mg/l CaCO₃. This is classified as "Hard" on the standard scale. You may notice limescale buildup in kettles and on taps.
Is St Helier tap water safe to drink?▾
Yes, tap water in St Helier is safe to drink. It is treated and tested by Thames Water and meets all UK Drinking Water Inspectorate standards. All tested parameters are within regulatory limits.
What is the water hardness in St Helier?▾
The water hardness in St Helier is 262 mg/l CaCO₃, which is classified as "Hard". This is above the UK national average of 170 mg/l.
Who supplies water to St Helier?▾
Water in St Helier is supplied by Thames Water, which serves the London and Thames Valley region. The water comes from river sources and is treated at Mitcham Treatment Works.