Tap water in SO51, Test ValleySafe to drink.Very hard.
Supplied by Southern Water. 24,373 samples, 22 substances, latest on 30 April 2026. Everything is inside the legal limit. One result, nitrate, sits close to the line.
9.0 / 10
The tank is as full as the score. The specks are the minerals that make water hard.
What to do about it
Hard water: compare softener quotes
At 276 mg/L a softener is the only thing that stops limescale. Filters do not soften water.
It pays for itself in most homes at this hardness, through a boiler that stays efficient and appliances that last.
Waterdrop G3P600 Reverse Osmosis
£550typical price
Removes nitrate, the result that stood out in SO51.
Osmio PRO-III Ultimate Whole House
£499typical price
Removes nitrate, the result that stood out in SO51.
We earn a commission if you buy through these links, at no extra cost to you. It never changes which product we put first. How we make money
What's in a glass of SO51 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.
Nitrate came closest to a limit, at 86% of it. 16 of 18 substances used under a quarter of theirs.
- Nitrate86%
- Nickel62%
- Colour15%
- Ammonia8%
- Trihalomethanes7%
- Aluminium6%
- Iron5%
- Lead4%
- Manganese4%
- Turbidity3%
- Selenium3%
- Antimony2%
- Nitrite2%
- Arsenic1%
- Bromate1%
- Cadmium<1%
- Copper<1%
- Chromium<1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 567 µS/cm
- pH 7.9 pH
All 22 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrate | 43 mg/L | 50 mg/L | 86% |
| Turbidity | 0.13 NTU | 4 NTU | 3% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| E. coli | 0 count/100ml | Must be zero | None found |
| Iron | 0.00928 mg/L | 0.2 mg/L | 5% |
| Ammonia | 0.039 mg/L | 0.5 mg/L | 8% |
| Aluminium | 0.0113 mg/L | 0.2 mg/L | 6% |
| Manganese | 0.00178 mg/L | 0.05 mg/L | 4% |
| Copper | 0.0084 mg/L | 2 mg/L | <1% |
| Lead | 0.00042 mg/L | 0.01 mg/L | 4% |
| Conductivity | 567 µS/cm | No legal limit | – |
| Colour | 3 mg/L Pt/Co | 20 mg/L Pt/Co | 15% |
| pH | 7.9 pH | No legal limit | – |
| Nitrite | 0.009 mg/L | 0.5 mg/L | 2% |
| Arsenic | 0.00015 mg/L | 0.01 mg/L | 1% |
| Cadmium | 0.000031 mg/L | 0.005 mg/L | <1% |
| Chromium | 0.00019 mg/L | 0.05 mg/L | <1% |
| Nickel | 0.0123 mg/L | 0.02 mg/L | 62% |
| Antimony | 0.000092 mg/L | 0.005 mg/L | 2% |
| Selenium | 0.00115 mg/L | 0.04 mg/L | 3% |
| Bromate | 0.00013 mg/L | 0.01 mg/L | 1% |
| Trihalomethanes | 0.00681 mg/L | 0.1 mg/L | 7% |
276mg of limescale minerals in every litre
This is the water that furs up kettles
Very hard on the UK scale. It is fine to drink. It is hard on boilers, showers, skin and anything that heats water, and a jug or tap filter will not change that.
Softener quotes for SO51
Leave your details and we will email you when we can match you with installers who cover SO51. No obligation.
Request a free assessment and we'll come back to you with local installer options for your area.
100%
free, no obligation
shared only with your consent
Your river is the Test - conf Dun to Tadburn Lake, rated moderate
The Environment Agency rated the Test - conf Dun to Tadburn Lake as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. 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
154
forever-chemical detections in nearby rivers and groundwater
At 5 sites. The highest was PFOS at 0.011 µg/L, at Tadburn Lake at Romsey By-Pass, 1.2 km away, in March 2024. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Southampton · Which filters remove PFAS · PFAS explained
SO51 in short
Tap water in SO51 (Test Valley) is supplied by Southern Water in the Test Valley Central zone and scores 9.0 out of 10, against an England and Wales average of 9.0. 1 of 22 tested substances was close to or over a limit. The latest sample is from 30 April 2026.
- Nitrate is within its legal limit but flagged, at 86% of the 50 mg/L maximumAnything over three quarters of a limit is flagged here as worth watching. It has not gone over. See every reading
- The lowest score of the 5 areas tested in Test ValleySO51 scores 9 out of 10. The best in Test Valley, SP10, scores 9.4.
- Every one of the 4 neighbouring districts scores higherSP10 next door scores 9.4, against 9 here. Supply zones, not distance, explain the gap. See SP10
Questions about SO51 water
Is SO51 tap water safe to drink?
Based on the latest tests, SO51 (Test Valley) water scores 9/10, which is safe. 1 of 22 tested contaminants exceeded recommended levels. Water is supplied by Southern Water.
What contaminants are in SO51 water?
We tested 22 contaminants in SO51 water. 1 were flagged, including Nitrate. 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 SO51?
SO51 (Test Valley) is supplied by Southern Water. You can view their full profile and compliance data on our supplier page.
Is SO51 water hard or soft?
Water in SO51 (Test Valley) has a hardness of 276 mg/L CaCO3, which is classified as very hard. Hard water can cause limescale buildup. A water softener or filter jug may help.
Should I use a water filter in SO51?
With 1 contaminant above recommended levels in SO51, a water filter could help. A reverse osmosis or activated carbon filter is recommended for PFAS removal. See our filter recommendations for your area.
Are there PFAS forever chemicals in SO51 water?
The tap-water tests we hold for SO51 do not include a PFAS result. Environment Agency monitoring found PFAS in 154 river and groundwater samples from 5 sites within 10 km of SO51, the highest being PFOS at 0.011 µg/L about 1.2 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 SO51?
The Environment Agency rated the Test - conf Dun to Tadburn Lake as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. 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 SO51, 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
- Best Water Softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared, with real costs
- Do I Need a Water Softener?The hardness bands, the symptoms, and a postcode check
- UK Water Hardness MapIs your water hard or soft, and does it matter?
- Best Water Filters UKEvery filter type compared on what it actually removes
- Do I need a water softener?The hardness bands, the symptoms, and when the answer is no
- Best water softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared
- Water softener costUnit, fitting and salt, and how long the payback takes
- Installation explainedWhere it goes, the bypass tap, the drain, DIY or plumber
- Harvey vs KineticoThe two premium twin-cylinder brands, side by side
- Softener salt guideTablet, block or granular, and how much you get through
- Salt-free softenersConditioners and electronic descalers, honestly assessed
PFAS explainedNitrate levelsHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SO51
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.
Get alerts for your area
We'll email you when water quality data changes for SO51.