Water Hardness and Quality in St John's
Supplied by Thames Water · Lewisham South (SLE43)
St John's has hard water with quality that meets all UK drinking water standards.
Check a specific postcode in St John's
Water Quality Scorecard
Total Hardness
Guideline: 150+ mg/l is considered hard
279mg/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
0.52mg/l
UK Average: 0.45 mg/lAbove Average
LowAverageHigh
Nitrate
UK Standard: max 50 mg/l
24mg/l
UK Average: 16.9 mg/lAbove Average
LowAverageHigh
Lead
UK Standard: max 10 µg/l
1.4µg/l
UK Average: 1.08 µg/lWell Above Average
LowAverageHigh
Fluoride
UK Standard: max 1.5 mg/l
0.16mg/l
UK Average: 0.19 mg/lWell Above Average
LowAverageHigh
Water Hardness in St John's
Hardness is the most searched water quality metric. It affects limescale buildup in kettles, boilers, and pipes.
279mg/l CaCO₃Hard
Soft
Mod. Soft
Slightly Hard
Mod. Hard
Hard
Very Hard
St John's has hard water at 279 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
- Lewisham South (SLE43)
- Source Type
- River
- Treatment Works
- Lewisham South Treatment Works
- Last Tested
- 2025-12-31
- Data Source
- Thames Water
Frequently Asked Questions
Is the water hard in St John's?▾
Yes, St John's has hard water at 279 mg/l CaCO₃. This is classified as "Hard" on the standard scale. You may notice limescale buildup in kettles and on taps.
Is St John's tap water safe to drink?▾
Yes, tap water in St John's 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 John's?▾
The water hardness in St John's is 279 mg/l CaCO₃, which is classified as "Hard". This is above the UK national average of 170 mg/l.
Who supplies water to St John's?▾
Water in St John's is supplied by Thames Water, which serves the London and Thames Valley region. The water comes from river sources and is treated at Lewisham South Treatment Works.