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tapwater
England and Wales average 9.0

Tap water in SO18, SouthamptonSafe to drink.Very hard.

Supplied by Southern Water. 27,548 samples, 25 substances, latest on 30 April 2026. Everything is inside the legal limit, and nothing comes close to it.

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9.4 / 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.

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What's in a glass of SO18 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 51% of it. 20 of 21 substances used under a quarter of theirs.

0%25%50%75%limitLegal limitChromium: 0.00019 mg/L, <1% of the 0.05 mg/L limitChromium<1%Cadmium: 0.000031 mg/L, <1% of the 0.005 mg/L limitCadmium<1%Antimony: 0.000049 mg/L, <1% of the 0.005 mg/L limitAntimony<1%Selenium: 0.00043 mg/L, 1% of the 0.04 mg/L limitSelenium1%Lead: 0.00014 mg/L, 1% of the 0.01 mg/L limitLead1%Nitrite: 0.009 mg/L, 2% of the 0.5 mg/L limitNitrite2%Turbidity: 0.13 NTU, 3% of the 4 NTU limitTurbidity3%Manganese: 0.00178 mg/L, 4% of the 0.05 mg/L limitManganese4%Mercury: 0.00004 mg/L, 4% of the 0.001 mg/L limitMercury4%Boron: 0.04 mg/L, 4% of the 1 mg/L limitBoron4%Bromate: 0.00042 mg/L, 4% of the 0.01 mg/L limitBromate4%Iron: 0.00928 mg/L, 5% of the 0.2 mg/L limitIron5%Fluoride: 0.08 mg/L, 5% of the 1.5 mg/L limitFluoride5%Aluminium: 0.0113 mg/L, 6% of the 0.2 mg/L limitAluminium6%Nickel: 0.00121 mg/L, 6% of the 0.02 mg/L limitNickel6%Arsenic: 0.00065 mg/L, 7% of the 0.01 mg/L limitArsenic7%Ammonia: 0.039 mg/L, 8% of the 0.5 mg/L limitAmmonia8%Trihalomethanes: 0.0081 mg/L, 8% of the 0.1 mg/L limitTrihalomethanes8%Copper: 0.162 mg/L, 8% of the 2 mg/L limitCopper8%Colour: 3 mg/L Pt/Co, 15% of the 20 mg/L Pt/Co limitColour15%Nitrate: 25.6 mg/L, 51% of the 50 mg/L limitNitrate51%
  1. Nitrate51%
  2. Colour15%
  3. Copper8%
  4. Trihalomethanes8%
  5. Ammonia8%
  6. Arsenic7%
  7. Nickel6%
  8. Aluminium6%
  9. Fluoride5%
  10. Iron5%
  11. Bromate4%
  12. Mercury4%
  13. Boron4%
  14. Manganese4%
  15. Turbidity3%
  16. Nitrite2%
  17. Lead1%
  18. Selenium1%
  19. Antimony<1%
  20. Cadmium<1%
  21. Chromium<1%
  • pH 7.4 pH
  • Coliform Bacteria none found
  • E. coli none found
  • Conductivity 545 µS/cm
All 25 results as a table
SubstanceResultLegal limitShare of limit
pH7.4 pHNo legal limit–
Aluminium0.0113 mg/L0.2 mg/L
6%
Iron0.00928 mg/L0.2 mg/L
5%
Manganese0.00178 mg/L0.05 mg/L
4%
Coliform Bacteria0 count/100mlMust be zeroNone found
E. coli0 count/100mlMust be zeroNone found
Colour3 mg/L Pt/Co20 mg/L Pt/Co
15%
Turbidity0.13 NTU4 NTU
3%
Nitrate25.6 mg/L50 mg/L
51%
Ammonia0.039 mg/L0.5 mg/L
8%
Copper0.162 mg/L2 mg/L
8%
Lead0.00014 mg/L0.01 mg/L
1%
Conductivity545 µS/cmNo legal limit–
Trihalomethanes0.0081 mg/L0.1 mg/L
8%
Bromate0.00042 mg/L0.01 mg/L
4%
Arsenic0.00065 mg/L0.01 mg/L
7%
Cadmium0.000031 mg/L0.005 mg/L
<1%
Chromium0.00019 mg/L0.05 mg/L
<1%
Nickel0.00121 mg/L0.02 mg/L
6%
Antimony0.000049 mg/L0.005 mg/L
<1%
Selenium0.00043 mg/L0.04 mg/L
1%
Nitrite0.009 mg/L0.5 mg/L
2%
Fluoride0.08 mg/L1.5 mg/L
5%
Mercury0.00004 mg/L0.001 mg/L
4%
Boron0.04 mg/L1 mg/L
4%

276mg of limescale minerals in every litre, typical for the SO area. SO18 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.

Soft400 mg/L

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Outside your tap

Your river is the Itchen, rated good

The Environment Agency rated the Itchen as good for ecological health in its 2025 assessment, meaning the river is only slightly changed from its natural state. 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

Within 10 km

204

forever-chemical detections in nearby rivers and groundwater

At 5 sites. The highest was PFOS at 0.0059 µg/L, at RSN1377 West Common Stream at Imber Way, 2.6 km away, in October 2025. These are river and borehole samples, not tests of your tap water.

Every PFAS sample around Southampton · Which filters remove PFAS · PFAS explained

SO18 in short

Tap water in SO18 (Southampton) is supplied by Southern Water in the Southampton Central zone and scores 9.4 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 30 April 2026.

  • The cleanest tap water of the 6 areas tested in SouthamptonSO18 scores 9.4 out of 10, ahead of SO15 in second place on 9.3. Every area in Southampton
  • Nitrate is the reading closest to its limit, at 51% of the 50 mg/L maximumIt passed with room to spare, and everything else tested sat further below its limit. 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

Next door

SO179.3 out of 10 · 276 mg/LSO159.3 out of 10 · 276 mg/LSO169.3 out of 10 · 276 mg/LSO148.9 out of 10 · 276 mg/LSO199.3 out of 10 · 276 mg/LSO508.4 out of 10 · 276 mg/L

Questions about SO18 water

Is SO18 tap water safe to drink?

Based on the latest tests, SO18 (Southampton) water scores 9.4/10, which is safe. 0 of 25 tested contaminants exceeded recommended levels. Water is supplied by Southern Water.

What contaminants are in SO18 water?

We tested 25 contaminants in SO18 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 SO18?

SO18 (Southampton) is supplied by Southern Water. You can view their full profile and compliance data on our supplier page.

Is SO18 water hard or soft?

No hardness reading has been published for SO18 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 SO18?

SO18 water scored 9.4/10 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 SO18 water?

The tap-water tests we hold for SO18 do not include a PFAS result. Environment Agency monitoring found PFAS in 204 river and groundwater samples from 5 sites within 10 km of SO18, the highest being PFOS at 0.0059 µg/L about 2.6 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 SO18?

The Environment Agency rated the Itchen as good for ecological health in its 2025 assessment, meaning the river is only slightly changed from its natural state. 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 SO18, which is treated before it reaches homes.

Keep reading

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 SO18

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.

SubstanceReadingDrinking water limit
pH8.27 pHNone
Temperature15.4 °CNone
Conductivity609 µS/cmNone
Nitrate7.8 mg/L50 mg/L
Nitrite0.011 mg/L0.5 mg/L
Phosphate0.035 mg/LNone
Dissolved Oxygen10 mg/LNone
Zinc0.0013 mg/LNone
Nickel0.00077 mg/L0.02 mg/L
Turbidity1.3 NTU4 NTU
Copper0.00088 mg/L2 mg/L
Ammonia0.14 mg/L0.5 mg/L

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We'll email you when water quality data changes for SO18.

Source: Southern Water test results, published through the Stream Water Data Portal; rivers and PFAS from the Environment Agency. Page updated . How we score · Where the data comes from