Tap water in SO16, SouthamptonSafe to drink.Very hard.
Supplied by Southern Water. 32,116 samples, 25 substances, latest on 29 April 2026. Everything is inside the legal limit, and nothing comes close to it.
9.3 / 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.
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
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What's in a glass of SO16 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 75% of it. 20 of 21 substances used under a quarter of theirs.
- Nitrate75%
- Trihalomethanes19%
- Colour15%
- Ammonia8%
- Aluminium6%
- Fluoride5%
- Nickel5%
- Bromate5%
- Iron5%
- Mercury4%
- Manganese4%
- Turbidity3%
- Boron2%
- Nitrite2%
- Arsenic2%
- Antimony1%
- Selenium1%
- Lead<1%
- Cadmium<1%
- Chromium<1%
- Copper<1%
- pH 7.5 pH
- Coliform Bacteria none found
- E. coli none found
- Conductivity 562 µS/cm
All 25 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Colour | 3 mg/L Pt/Co | 20 mg/L Pt/Co | 15% |
| Turbidity | 0.13 NTU | 4 NTU | 3% |
| pH | 7.5 pH | No legal limit | – |
| Aluminium | 0.0113 mg/L | 0.2 mg/L | 6% |
| Iron | 0.00928 mg/L | 0.2 mg/L | 5% |
| Manganese | 0.00178 mg/L | 0.05 mg/L | 4% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| E. coli | 0 count/100ml | Must be zero | None found |
| Conductivity | 562 µS/cm | No legal limit | – |
| Lead | 0.00009 mg/L | 0.01 mg/L | <1% |
| Nitrate | 37.4 mg/L | 50 mg/L | 75% |
| Trihalomethanes | 0.0194 mg/L | 0.1 mg/L | 19% |
| Ammonia | 0.039 mg/L | 0.5 mg/L | 8% |
| Copper | 0.0043 mg/L | 2 mg/L | <1% |
| Bromate | 0.00049 mg/L | 0.01 mg/L | 5% |
| Nitrite | 0.009 mg/L | 0.5 mg/L | 2% |
| Arsenic | 0.00018 mg/L | 0.01 mg/L | 2% |
| Cadmium | 0.000031 mg/L | 0.005 mg/L | <1% |
| Chromium | 0.00019 mg/L | 0.05 mg/L | <1% |
| Nickel | 0.00104 mg/L | 0.02 mg/L | 5% |
| Antimony | 0.000063 mg/L | 0.005 mg/L | 1% |
| Selenium | 0.00045 mg/L | 0.04 mg/L | 1% |
| Fluoride | 0.08 mg/L | 1.5 mg/L | 5% |
| Mercury | 0.00004 mg/L | 0.001 mg/L | 4% |
| Boron | 0.0191 mg/L | 1 mg/L | 2% |
276mg of limescale minerals in every litre, typical for the SO area. SO16 has no reading of its own.
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 SO16
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Your river is the Tanner's Brook, rated moderate
The Environment Agency rated the Tanner's Brook as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by fish 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
257
forever-chemical detections in nearby rivers and groundwater
At 8 sites. The highest was PFOS at 0.011 µg/L, at Tadburn Lake at Romsey By-Pass, 7.1 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
SO16 in short
Tap water in SO16 (Southampton) is supplied by Southern Water in the Southampton Central zone and scores 9.3 out of 10, against an England and Wales average of 9.0. None of the 25 tested substances came close to a limit. The latest sample is from 29 April 2026.
- Nitrate is the reading closest to its limit, at 75% of the 50 mg/L maximumIt passed, but with less headroom than anything else tested here. Worth watching in the next round of results. See every reading
- Very hard water at 276 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles across the SO postcode area. How hardness is measured
- 3rd cleanest of 6 areas tested in SouthamptonSquarely mid-table for Southampton, between SO18 on 9.4 and SO14 on 8.9. Every area in Southampton
Questions about SO16 water
Is SO16 tap water safe to drink?
Based on the latest tests, SO16 (Southampton) water scores 9.3/10, which is safe. 0 of 25 tested contaminants exceeded recommended levels. Water is supplied by Southern Water.
What contaminants are in SO16 water?
We tested 25 contaminants in SO16 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 SO16?
SO16 (Southampton) is supplied by Southern Water. You can view their full profile and compliance data on our supplier page.
Is SO16 water hard or soft?
No hardness reading has been published for SO16 itself. Across the SO postcode area the typical value is 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 SO16?
SO16 water scored 9.3/10 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 SO16 water?
The tap-water tests we hold for SO16 do not include a PFAS result. Environment Agency monitoring found PFAS in 257 river and groundwater samples from 8 sites within 10 km of SO16, the highest being PFOS at 0.011 µg/L about 7.1 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 SO16?
The Environment Agency rated the Tanner's Brook as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by fish 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 SO16, 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?
- 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 explainedHow to test your waterBest water filtersFilter shower headsWater testing kitsAll of SouthamptonUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SO16
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 | 7.88 pH | None |
| Temperature | 15.2 °C | None |
| Conductivity | 551 µS/cm | None |
| Nitrate | 6.7 mg/L | 50 mg/L |
| Nitrite | 0.0073 mg/L | 0.5 mg/L |
| Phosphate | 0.04 mg/L | None |
| Dissolved Oxygen | 8.46 mg/L | None |
| Zinc | 0.0022 mg/L | None |
| Nickel | 0.001 mg/L | 0.02 mg/L |
| Turbidity | 1.8 NTU | 4 NTU |
| Copper | 0.0014 mg/L | 2 mg/L |
| Iron | 0.042 mg/L | 0.2 mg/L |
| Ammonia | 0.036 mg/L | 0.5 mg/L |
| PFAS (total) | 0.00095 µg/L | None |
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