Tap water in WD17, WatfordNitrite is over the limit.Very hard.
Supplied by Thames Water. 71 samples, 23 substances, latest on 31 December 2025. Nitrite came in above the legal limit. Everything else passed.
8.5 / 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 289 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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Waterdrop 10UA Under Sink
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What's in a glass of WD17 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 124% of it.
- Nitrite124%
- Nitrate62%
- Trihalomethanes13%
- Bromate10%
- Lead9%
- Colour9%
- Fluoride9%
- Cadmium8%
- Mercury7%
- Arsenic7%
- Antimony6%
- Nickel6%
- Chromium5%
- Iron5%
- Aluminium4%
- Boron4%
- Copper4%
- Selenium1%
- Manganese1%
- Coliform Bacteria none found
- E. coli none found
- Conductivity 561 µS/cm
All 23 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| Nitrite | 0.62 mg/L | 0.5 mg/L | 124% |
| Coliform Bacteria | 0 count/100ml | Must be zero | None found |
| E. coli | 0 count/100ml | Must be zero | None found |
| Colour | 1.8 mg/L Pt/Co | 20 mg/L Pt/Co | 9% |
| Conductivity | 561 µS/cm | No legal limit | – |
| Fluoride | 0.13 mg/L | 1.5 mg/L | 9% |
| Nitrate | 31.1 mg/L | 50 mg/L | 62% |
| Hardness (as CaCO3) | 289 mg/L | No legal limit | – |
| Aluminium | 0.0082 mg/L | 0.2 mg/L | 4% |
| Antimony | 0.0003 mg/L | 0.005 mg/L | 6% |
| Arsenic | 0.0007 mg/L | 0.01 mg/L | 7% |
| Boron | 0.04 mg/L | 1 mg/L | 4% |
| Cadmium | 0.0004 mg/L | 0.005 mg/L | 8% |
| Chromium | 0.0025 mg/L | 0.05 mg/L | 5% |
| Copper | 0.07 mg/L | 2 mg/L | 4% |
| Iron | 0.009 mg/L | 0.2 mg/L | 5% |
| Lead | 0.0009 mg/L | 0.01 mg/L | 9% |
| Manganese | 0.0006 mg/L | 0.05 mg/L | 1% |
| Mercury | 0.00007 mg/L | 0.001 mg/L | 7% |
| Nickel | 0.0011 mg/L | 0.02 mg/L | 6% |
| Selenium | 0.0005 mg/L | 0.04 mg/L | 1% |
| Trihalomethanes | 0.013 mg/L | 0.1 mg/L | 13% |
| Bromate | 0.001 mg/L | 0.01 mg/L | 10% |
289mg 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 WD17
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Your river is the Colne (from Confluence with Ver to Gade), rated moderate
The Environment Agency rated the Colne (from Confluence with Ver to Gade) as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and water plants and algae. 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
WD17 in short
Tap water in WD17 (Watford) is supplied by Thames Water in the Watford Central zone and scores 8.5 out of 10, against an England and Wales average of 9.0. 1 of 23 tested substances was close to or over a limit. The latest sample is from 31 December 2025.
- Nitrite was measured at 0.62 mg/L, 24% over the UK limitIt is the only one of 23 tested substances to go over its limit. See the full results
- Very hard water at 289 mg/LThe threshold for very hard is 250 mg/L. Expect visible limescale on taps and in kettles in WD17. How hardness is measured
- 2nd cleanest of 4 areas tested in WatfordOnly 1 area in Watford scored higher. The best is WD25 on 8.7.
Questions about WD17 water
Is WD17 tap water safe to drink?
Based on the latest tests, WD17 (Watford) water scores 8.5/10, which is safe. 1 of 23 tested contaminants exceeded recommended levels. Water is supplied by Thames Water.
What contaminants are in WD17 water?
We tested 23 contaminants in WD17 water. 1 were flagged, including Nitrite.
Who supplies water in WD17?
WD17 (Watford) is supplied by Thames Water. You can view their full profile and compliance data on our supplier page.
Is WD17 water hard or soft?
Water in WD17 (Watford) has a hardness of 289 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 WD17?
With 1 contaminant above recommended levels in WD17, 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 WD17 water?
No PFAS (forever chemicals) result is attached to the tap-water tests for WD17, 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 WD17?
The Environment Agency rated the Colne (from Confluence with Ver to Gade) as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by phosphate and water plants and algae. 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 WD17, 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?
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- Salt-free softenersConditioners and electronic descalers, honestly assessed
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River and groundwater readings near WD17
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 WD17.