Tap water in SG3, North HertfordshireSafe to drink.Very hard.
Supplied by Affinity Water. 541 samples, 24 substances, latest on 18 December 2025. Everything is inside the legal limit, and nothing comes close to it.
9.1 / 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 296 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 SG3 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 61% of it. 19 of 21 substances used under a quarter of theirs.
- Nitrate61%
- Trihalomethanes35%
- Fluoride17%
- Nickel15%
- Bromate15%
- Ammonia12%
- Colour10%
- Boron10%
- Antimony9%
- Lead7%
- Iron4%
- Arsenic3%
- Turbidity3%
- Mercury2%
- Nitrite2%
- Cadmium1%
- Aluminium<1%
- Selenium<1%
- Chromium<1%
- Manganese<1%
- Copper<1%
- E. coli none found
- Coliform Bacteria none found
- Conductivity 544 µS/cm
All 24 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrite | 0.01 mg/L | 0.5 mg/L | 2% |
| Nitrate | 30.3 mg/L | 50 mg/L | 61% |
| Bromate | 0.00147 mg/L | 0.01 mg/L | 15% |
| Manganese | 0.000363 mg/L | 0.05 mg/L | <1% |
| E. coli | 0 count/100ml | Must be zero | None found |
| Aluminium | 0.00199 mg/L | 0.2 mg/L | <1% |
| Ammonia | 0.06 mg/L | 0.5 mg/L | 12% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| Turbidity | 0.1 NTU | 4 NTU | 3% |
| Chromium | 0.000383 mg/L | 0.05 mg/L | <1% |
| Fluoride | 0.25 mg/L | 1.5 mg/L | 17% |
| Arsenic | 0.000322 mg/L | 0.01 mg/L | 3% |
| Cadmium | 0.000054 mg/L | 0.005 mg/L | 1% |
| Conductivity | 544 µS/cm | No legal limit | – |
| Iron | 0.00897 mg/L | 0.2 mg/L | 4% |
| Antimony | 0.00046 mg/L | 0.005 mg/L | 9% |
| Trihalomethanes | 0.0349 mg/L | 0.1 mg/L | 35% |
| Selenium | 0.000352 mg/L | 0.04 mg/L | <1% |
| Boron | 0.095 mg/L | 1 mg/L | 10% |
| Colour | 2 mg/L Pt/Co | 20 mg/L Pt/Co | 10% |
| Mercury | 0.000023 mg/L | 0.001 mg/L | 2% |
| Nickel | 0.00304 mg/L | 0.02 mg/L | 15% |
| Lead | 0.000673 mg/L | 0.01 mg/L | 7% |
| Copper | 0.005 mg/L | 2 mg/L | <1% |
296mg 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 SG3
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Your river is the Stevenage Brook, rated poor
The Environment Agency rated the Stevenage Brook as poor for ecological health in its 2025 assessment, meaning the river is badly affected, with much of the expected wildlife missing. It is held back by fish, water plants and algae 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
SG3 in short
Tap water in SG3 (North Hertfordshire) is supplied by Affinity Water in the North Hertfordshire Central zone and scores 9.1 out of 10, against an England and Wales average of 9.0. None of the 24 tested substances came close to a limit. The latest sample is from 18 December 2025.
- Nitrate is the reading closest to its limit, at 61% 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 296 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in SG3. How hardness is measured
- 3rd cleanest of 6 areas tested in North HertfordshireSquarely mid-table for North Hertfordshire, between SG6 on 9.3 and SG8 on 8.8.
Questions about SG3 water
Is SG3 tap water safe to drink?
Based on the latest tests, SG3 (North Hertfordshire) water scores 9.1/10, which is safe. 0 of 24 tested contaminants exceeded recommended levels. Water is supplied by Affinity Water.
What contaminants are in SG3 water?
We tested 24 contaminants in SG3 water. None exceeded recommended safe levels.
Who supplies water in SG3?
SG3 (North Hertfordshire) is supplied by Affinity Water. You can view their full profile and compliance data on our supplier page.
Is SG3 water hard or soft?
Water in SG3 (North Hertfordshire) has a hardness of 296 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 SG3?
SG3 water scored 9.1/10 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 SG3 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for SG3, 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 SG3?
The Environment Agency rated the Stevenage Brook as poor for ecological health in its 2025 assessment, meaning the river is badly affected, with much of the expected wildlife missing. It is held back by fish, water plants and algae 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 SG3, which is treated before it reaches homes.
Keep reading
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- UK Water Hardness MapIs your water hard or soft, and does it matter?
- Is UK Tap Water Safe?Everything you need to know about tap water safety in the UK
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- Best water softener UKHarvey, Kinetico, BWT, Monarch and Water2Buy compared
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- Installation explainedWhere it goes, the bypass tap, the drain, DIY or plumber
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- Softener salt guideTablet, block or granular, and how much you get through
- Salt-free softenersConditioners and electronic descalers, honestly assessed
How to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
River and groundwater readings near SG3
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 SG3.