Tap water in S21, North East DerbyshireSafe to drink.Moderately soft.
Supplied by Severn Trent. 840 samples, 20 substances, latest on 16 December 2025. Everything is inside the legal limit, and nothing comes close to it.
9.2 / 10
The tank is as full as the score. The specks are the minerals that make water hard.
What to do about it
ZeroWater 12-Cup Ready-Pour
£40typical price
Households concerned about PFAS and heavy metals
Waterdrop 10UA Under Sink
£70typical price
High-volume under-sink filtration without RO complexity
BRITA Marella XL + MAXTRA PRO
£25typical price
Basic chlorine and taste improvement on a budget
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What's in a glass of S21 water
Every bubble is a substance the lab measured. The higher it floats, the closer it came to its legal limit, the dashed line at the top.
Trihalomethanes came closest to a limit, at 33% of it. 15 of 17 substances used under a quarter of theirs.
- Trihalomethanes33%
- Fluoride29%
- Iron19%
- Nitrate12%
- Nickel11%
- Aluminium11%
- Colour7%
- Antimony5%
- Manganese3%
- Turbidity3%
- Arsenic2%
- Cadmium2%
- Lead1%
- Chromium<1%
- Selenium<1%
- Nitrite<1%
- Copper<1%
- pH 7.56 pH
- Conductivity 310 µS/cm
- Phosphate 0.956 mg/L
All 20 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Colour | 1.4 mg/L Pt/Co | 20 mg/L Pt/Co | 7% |
| Turbidity | 0.12 NTU | 4 NTU | 3% |
| pH | 7.56 pH | No legal limit | – |
| Nitrate | 5.8 mg/L | 50 mg/L | 12% |
| Nitrite | 0.003 mg/L | 0.5 mg/L | <1% |
| Manganese | 0.00168 mg/L | 0.05 mg/L | 3% |
| Copper | 0.0021 mg/L | 2 mg/L | <1% |
| Fluoride | 0.44 mg/L | 1.5 mg/L | 29% |
| Arsenic | 0.00023 mg/L | 0.01 mg/L | 2% |
| Cadmium | 0.0001 mg/L | 0.005 mg/L | 2% |
| Chromium | 0.00042 mg/L | 0.05 mg/L | <1% |
| Nickel | 0.0022 mg/L | 0.02 mg/L | 11% |
| Lead | 0.00014 mg/L | 0.01 mg/L | 1% |
| Antimony | 0.000225 mg/L | 0.005 mg/L | 5% |
| Selenium | 0.00032 mg/L | 0.04 mg/L | <1% |
| Aluminium | 0.021 mg/L | 0.2 mg/L | 11% |
| Iron | 0.0382 mg/L | 0.2 mg/L | 19% |
| Conductivity | 310 µS/cm | No legal limit | – |
| Trihalomethanes | 0.0334 mg/L | 0.1 mg/L | 33% |
| Phosphate | 0.956 mg/L | No legal limit | – |
88mg of limescale minerals in every litre, typical for the S area. S21 has no reading of its own.
Soft water. Kind to kettles, boilers and skin
You will not need a softener here, and you will use less soap and detergent than most of England.
Your river is the Rother, Doe Lea to Don, rated moderate
The Environment Agency rated the Rother, Doe Lea to Don as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and insects and other small river life. It fails the chemical test, as every river, estuary and stretch of coast in England does, because of long-lasting pollutants such as mercury, PFOS (a forever chemical) and old flame retardants.
None of this is a test of your tap water. Environment Agency record · River health across England
12
forever-chemical detections in nearby rivers and groundwater
At 1 site. The highest was PFOA at 0.0055 µg/L, at RSN1172 River Drone Us Sheffield Road, 9.1 km away, in July 2024. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Sheffield · Which filters remove PFAS · PFAS explained
S21 in short
Tap water in S21 (North East Derbyshire) is supplied by Severn Trent in the North East Derbyshire Central zone and scores 9.2 out of 10, against an England and Wales average of 9.0. None of the 20 tested substances came close to a limit. The latest sample is from 16 December 2025.
- 2nd cleanest of 4 areas tested in North East DerbyshireOnly 1 area in North East Derbyshire scored higher. The best is S18 on 9.4.
- PFAS found at 1 monitoring site within 10 kmThose are river and groundwater samples, not tap water. The highest was PFOA about 9.1 km away. What was measured
- Nothing tested came within 40% of its legal limitThe highest was Trihalomethanes at 33% of the 0.1 mg/L maximum. See every reading
Questions about S21 water
Is S21 tap water safe to drink?
Based on the latest tests, S21 (North East Derbyshire) water scores 9.2/10, which is safe. 0 of 20 tested contaminants exceeded recommended levels. Water is supplied by Severn Trent.
What contaminants are in S21 water?
We tested 20 contaminants in S21 water. None exceeded recommended safe levels. PFAS (forever chemicals) were also measured in rivers and groundwater within 10 km, though not in the tap-water tests themselves.
Who supplies water in S21?
S21 (North East Derbyshire) is supplied by Severn Trent. You can view their full profile and compliance data on our supplier page.
Is S21 water hard or soft?
No hardness reading has been published for S21 itself. Across the S postcode area the typical value is 88 mg/L CaCO3, which is classified as moderately soft. This is a moderate hardness level.
Should I use a water filter in S21?
S21 water scored 9.2/10 with no contaminants above recommended levels. A filter is optional but can improve taste, especially if you notice a chlorine flavour. See our filter recommendations for your area.
Are there PFAS forever chemicals in S21 water?
The tap-water tests we hold for S21 do not include a PFAS result. Environment Agency monitoring found PFAS in 12 river and groundwater samples from 1 sites within 10 km of S21, the highest being PFOA at 0.0055 µg/L about 9.1 km away. These are environmental samples, not tests of tap water. The UK currently has no legal limit for PFAS in drinking water; the Drinking Water Inspectorate uses a 0.1 µg/L guideline for individual compounds. Reverse osmosis filters can reduce PFAS levels.
How clean is the river near S21?
The Environment Agency rated the Rother, Doe Lea to Don as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and insects and other small river life. It fails the chemical test, as every river, estuary and stretch of coast in England does, because of long-lasting pollutants such as mercury, PFOS (a forever chemical) and old flame retardants. This is a rating of the river, not of tap water in S21, which is treated before it reaches homes.
Keep reading
- Best Filter for PFAS RemovalThe filters with independent certification to remove forever chemicals
- PFAS Forever ChemicalsWhat PFAS are and how to reduce your exposure at home
- Is UK Tap Water Safe?Everything you need to know about tap water safety in the UK
- Best Water Filters UKEvery filter type compared on what it actually removes
PFAS explainedHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near S21
Environment Agency samples from rivers, groundwater and reservoirs nearby. Not your tap water. For scale they are shown against drinking water limits; rivers are judged against much stricter environmental standards, and on those every river in England fails for chemicals.
| Substance | Reading | Drinking water limit |
|---|---|---|
| pH | 7.71 pH | None |
| Temperature | 15.2 °C | None |
| Conductivity | 1887 µS/cm | None |
| Ammonia | 0.05 mg/L | 0.5 mg/L |
| Nitrate | 0.44 mg/L | 50 mg/L |
| Nitrite | 0.0072 mg/L | 0.5 mg/L |
| Dissolved Oxygen | 9.63 mg/L | None |
| Phosphate | 0.014 mg/L | None |
| Copper | 0.0034 mg/L | 2 mg/L |
| Zinc | 0.0208 mg/L | None |
| Iron | 0.09 mg/L | 0.2 mg/L |
| Hardness (as CaCO3) | 235 mg/L | None |
Get alerts for your area
We'll email you when water quality data changes for S21.