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tapwater
England and Wales average 9.0

Tap water in SG5, North HertfordshireNitrite is over the limit.Very hard.

Supplied by Affinity Water. 727 samples, 24 substances, latest on 19 December 2025. Nitrite came in above the legal limit. Everything else passed.

Get softener quotes for SG5See everything that was tested

8.9 / 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 368 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 SG5 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.

Nitrite is over its legal limit, at 148% of it.

0%25%50%75%limitLegal limitAntimony: 0.000031 mg/L, <1% of the 0.005 mg/L limitAntimony<1%Manganese: 0.000363 mg/L, <1% of the 0.05 mg/L limitManganese<1%Chromium: 0.000383 mg/L, <1% of the 0.05 mg/L limitChromium<1%Selenium: 0.000352 mg/L, <1% of the 0.04 mg/L limitSelenium<1%Aluminium: 0.00199 mg/L, <1% of the 0.2 mg/L limitAluminium<1%Cadmium: 0.000054 mg/L, 1% of the 0.005 mg/L limitCadmium1%Copper: 0.038 mg/L, 2% of the 2 mg/L limitCopper2%Arsenic: 0.000216 mg/L, 2% of the 0.01 mg/L limitArsenic2%Mercury: 0.000023 mg/L, 2% of the 0.001 mg/L limitMercury2%Turbidity: 0.1 NTU, 3% of the 4 NTU limitTurbidity3%Nickel: 0.000866 mg/L, 4% of the 0.02 mg/L limitNickel4%Iron: 0.00897 mg/L, 4% of the 0.2 mg/L limitIron4%Boron: 0.046 mg/L, 5% of the 1 mg/L limitBoron5%Trihalomethanes: 0.0054 mg/L, 5% of the 0.1 mg/L limitTrihalomethanes5%Lead: 0.000673 mg/L, 7% of the 0.01 mg/L limitLead7%Fluoride: 0.121 mg/L, 8% of the 1.5 mg/L limitFluoride8%Colour: 2 mg/L Pt/Co, 10% of the 20 mg/L Pt/Co limitColour10%Ammonia: 0.06 mg/L, 12% of the 0.5 mg/L limitAmmonia12%Bromate: 0.00147 mg/L, 15% of the 0.01 mg/L limitBromate15%Nitrate: 36.9 mg/L, 74% of the 50 mg/L limitNitrate74%Nitrite: 0.738 mg/L, 148% of the 0.5 mg/L limitNitrite148%
  1. Nitrite148%
  2. Nitrate74%
  3. Bromate15%
  4. Ammonia12%
  5. Colour10%
  6. Fluoride8%
  7. Lead7%
  8. Trihalomethanes5%
  9. Boron5%
  10. Iron4%
  11. Nickel4%
  12. Turbidity3%
  13. Mercury2%
  14. Arsenic2%
  15. Copper2%
  16. Cadmium1%
  17. Aluminium<1%
  18. Selenium<1%
  19. Chromium<1%
  20. Manganese<1%
  21. Antimony<1%
  • E. coli none found
  • Coliform Bacteria none found
  • Conductivity 504 µS/cm
All 24 results as a table
SubstanceResultLegal limitShare of limit
Nitrite0.738 mg/L0.5 mg/L
148%
E. coli0 count/100mlMust be zeroNone found
Trihalomethanes0.0054 mg/L0.1 mg/L
5%
Chromium0.000383 mg/L0.05 mg/L
<1%
Fluoride0.121 mg/L1.5 mg/L
8%
Coliform Bacteria0 count/100mlMust be zeroNone found
Ammonia0.06 mg/L0.5 mg/L
12%
Conductivity504 µS/cmNo legal limit–
Manganese0.000363 mg/L0.05 mg/L
<1%
Iron0.00897 mg/L0.2 mg/L
4%
Boron0.046 mg/L1 mg/L
5%
Lead0.000673 mg/L0.01 mg/L
7%
Turbidity0.1 NTU4 NTU
3%
Antimony0.000031 mg/L0.005 mg/L
<1%
Mercury0.000023 mg/L0.001 mg/L
2%
Cadmium0.000054 mg/L0.005 mg/L
1%
Nitrate36.9 mg/L50 mg/L
74%
Aluminium0.00199 mg/L0.2 mg/L
<1%
Colour2 mg/L Pt/Co20 mg/L Pt/Co
10%
Selenium0.000352 mg/L0.04 mg/L
<1%
Arsenic0.000216 mg/L0.01 mg/L
2%
Nickel0.000866 mg/L0.02 mg/L
4%
Bromate0.00147 mg/L0.01 mg/L
15%
Copper0.038 mg/L2 mg/L
2%

368mg 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.

Soft400 mg/L

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Outside your tap

Your river is the Hiz (DS Hitchin), rated moderate

The Environment Agency rated the Hiz (DS Hitchin) 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. 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

SG5 in short

Tap water in SG5 (North Hertfordshire) is supplied by Affinity Water in the North Hertfordshire Central zone and scores 8.9 out of 10, against an England and Wales average of 9.0. 1 of 24 tested substances was close to or over a limit. The latest sample is from 19 December 2025.

  • Nitrite was measured at 0.74 mg/L, 48% over the UK limitIt is the only one of 24 tested substances to go over its limit. See the full results
  • Among the hardest water in the country at 368 mg/LVery hard starts at 250 mg/L. At this level kettles scale up within weeks and a softener is a normal purchase in SG5. How hardness is measured
  • 5th cleanest of 6 areas tested in North Hertfordshire1 area in North Hertfordshire scored lower. The best is SG6 on 9.3.

Next door

SG39.1 out of 10 · 296 mg/LSG79.3 out of 10 · 323 mg/LSG88.8 out of 10 · 273 mg/LSG69.3 out of 10 · 294 mg/LSG48.9 out of 10 · 368 mg/LSG168.5 out of 10 · 285 mg/LSG158.8 out of 10 · 302 mg/L

Questions about SG5 water

Is SG5 tap water safe to drink?

Based on the latest tests, SG5 (North Hertfordshire) water scores 8.9/10, which is safe. 1 of 24 tested contaminants exceeded recommended levels. Water is supplied by Affinity Water.

What contaminants are in SG5 water?

We tested 24 contaminants in SG5 water. 1 were flagged, including Nitrite.

Who supplies water in SG5?

SG5 (North Hertfordshire) is supplied by Affinity Water. You can view their full profile and compliance data on our supplier page.

Is SG5 water hard or soft?

Water in SG5 (North Hertfordshire) has a hardness of 368 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 SG5?

With 1 contaminant above recommended levels in SG5, a water filter could help. A filter jug or under-sink filter can reduce most common contaminants. See our filter recommendations for your area.

Are there PFAS forever chemicals in SG5 water?

No PFAS (forever chemicals) result is attached to the tap-water tests for SG5, and the Environment Agency has no PFAS detections in rivers or groundwater within 10 km of it. That reflects where sampling has happened as much as the water itself.

How clean is the river near SG5?

The Environment Agency rated the Hiz (DS Hitchin) 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. 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 SG5, which is treated before it reaches homes.

Keep reading

Nitrate levelsHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map

River and groundwater readings near SG5

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
Lead0.0078 mg/L0.01 mg/L
pH7.52 pHNone
Temperature14.6 °CNone
Conductivity735 µS/cmNone
Nitrate5.9 mg/L50 mg/L
Nitrite0.01 mg/L0.5 mg/L
Phosphate0.04 mg/LNone
Dissolved Oxygen8.32 mg/LNone
Ammonia0.067 mg/L0.5 mg/L
Iron0.069 mg/L0.2 mg/L
Chromium0.00056 mg/L0.05 mg/L
Copper0.002 mg/L2 mg/L
Zinc0.0081 mg/LNone
Nickel0.0013 mg/L0.02 mg/L
PFAS (total)0.0029 µg/LNone

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Source: Affinity 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