Tap water in DA4, SevenoaksToo few tap tests to call it.Very hard.
Supplied by South East Water. 13 substances, latest on 14 September 2026. These are river and groundwater samples near DA4, not tests of treated tap water, so treat the score as a rough guide.
8.4 / 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 273 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 DA4 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.
Ammonia came closest to a limit, at 42% of it. 4 of 5 substances used under a quarter of theirs.
- Ammonia42%
- Fluoride9%
- Nitrite3%
- Nitrate2%
- Lead2%
- Temperature 19 °C
- Phosphate 0.028 mg/L
- pH 0.11 pH
- Dissolved Oxygen 8.49 mg/L
- Conductivity 608 µS/cm
- Zinc 0.034 mg/L
- PFAS (total) 0.0048 µg/L
All 13 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Temperature | 19 °C | No legal limit | – |
| Nitrate | 1.1 mg/L | 50 mg/L | 2% |
| Nitrite | 0.014 mg/L | 0.5 mg/L | 3% |
| Phosphate | 0.028 mg/L | No legal limit | – |
| Ammonia | 0.21 mg/L | 0.5 mg/L | 42% |
| pH | 0.11 pH | No legal limit | – |
| Dissolved Oxygen | 8.49 mg/L | No legal limit | – |
| Lead | 0.00016 mg/L | 0.01 mg/L | 2% |
| Conductivity | 608 µS/cm | No legal limit | – |
| Hardness (as CaCO3) | 285 mg/L | No legal limit | – |
| Fluoride | 0.13 mg/L | 1.5 mg/L | 9% |
| Zinc | 0.034 mg/L | No legal limit | – |
| PFAS (total) | 0.0048 µg/L | No legal limit | – |
273mg of limescale minerals in every litre, typical for the DA area. DA4 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 DA4
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Your river is the Middle and Lower Darent, rated good
The Environment Agency rated the Middle and Lower Darent 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. Its ecological rating has improved since the previous assessment.
None of this is a test of your tap water. Environment Agency record · River health across England
DA4 in short
Tap water in DA4 (Sevenoaks) is supplied by South East Water in the Sevenoaks Central zone and scores 8.4 out of 10, against an England and Wales average of 9.0. None of the 13 tested substances came close to a limit. The latest sample is from 14 September 2026.
- The lowest score of the 7 areas tested in SevenoaksDA4 scores 8.4 out of 10. The best in Sevenoaks, TN16, scores 9.3.
- Very hard water at 273 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles across the DA postcode area. How hardness is measured
- Ammonia is the reading closest to its limit, at 42% of the 0.5 mg/L maximumIt passed with room to spare, and everything else tested sat further below its limit. See every reading
Questions about DA4 water
Is DA4 tap water safe to drink?
Based on the latest tests, DA4 (Sevenoaks) water scores 8.4/10, which is safe. 0 of 13 tested contaminants exceeded recommended levels. Water is supplied by South East Water.
What contaminants are in DA4 water?
We tested 13 contaminants in DA4 water. None exceeded recommended safe levels. PFAS (forever chemicals) were also detected at 0.0048 µg/L in nearby environmental monitoring.
Who supplies water in DA4?
DA4 (Sevenoaks) is supplied by South East Water. You can view their full profile and compliance data on our supplier page.
Is DA4 water hard or soft?
No hardness reading has been published for DA4 itself. Across the DA postcode area the typical value is 273 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 DA4?
DA4 water scored 8.4/10 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 DA4 water?
Yes, PFAS (per- and polyfluoroalkyl substances) have been detected in DA4 at 0.0048 µg/L from environmental monitoring. The UK currently has no legal limit for PFAS in drinking water. Reverse osmosis and activated carbon filters can reduce PFAS levels.
How clean is the river near DA4?
The Environment Agency rated the Middle and Lower Darent 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. Its ecological rating has improved since the previous assessment. This is a rating of the river, not of tap water in DA4, 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
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- 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 kitsUK water rankingsWater hardness checkerWater hardness map
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