Tap water in GU17, HartToo few tap tests to call it.Slightly hard.
Supplied by Southern Water. 10 substances, latest on 24 August 2026. These are river and groundwater samples near GU17, not tests of treated tap water, so treat the score as a rough guide.
8.3 / 10
The tank is as full as the score. The specks are the minerals that make water hard.
What to do about it
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BRITA Marella XL + MAXTRA PRO
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Basic chlorine and taste improvement on a budget
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What's in a glass of GU17 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.
Iron came closest to a limit, at 65% of it. 3 of 5 substances used under a quarter of theirs.
- Iron65%
- Nitrate32%
- Ammonia9%
- Nitrite2%
- Cadmium<1%
- pH 7.63 pH
- Temperature 15.1 °C
- Conductivity 732 µS/cm
- Phosphate 0.32 mg/L
- Dissolved Oxygen 8.16 mg/L
All 10 results as a table
| Substance | Result | Legal limit | Share of limit |
|---|---|---|---|
| pH | 7.63 pH | No legal limit | – |
| Temperature | 15.1 °C | No legal limit | – |
| Conductivity | 732 µS/cm | No legal limit | – |
| Nitrate | 16 mg/L | 50 mg/L | 32% |
| Nitrite | 0.0093 mg/L | 0.5 mg/L | 2% |
| Phosphate | 0.32 mg/L | No legal limit | – |
| Dissolved Oxygen | 8.16 mg/L | No legal limit | – |
| Cadmium | 0.00002 mg/L | 0.005 mg/L | <1% |
| Ammonia | 0.046 mg/L | 0.5 mg/L | 9% |
| Iron | 0.13 mg/L | 0.2 mg/L | 65% |
154mg of limescale minerals in every litre, typical for the GU area. GU17 has no reading of its own.
Middling hardness. Some scale, slowly
Below the point where a softener pays for itself. Descaling the kettle now and then is all most homes need.
Your river is the Blackwater (Hawley to Whitewater confluence at Bramshill), rated moderate
The Environment Agency rated the Blackwater (Hawley to Whitewater confluence at Bramshill) as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by water plants and algae and phosphate. 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
40
forever-chemical detections in nearby rivers and groundwater
At 1 site. The highest was PFPeA at 0.0061 µg/L, at Hart at Lea Bridge, Hazeley, 9.7 km away, in October 2023. These are river and borehole samples, not tests of your tap water.
Every PFAS sample around Reading · Which filters remove PFAS · PFAS explained
GU17 in short
Tap water in GU17 (Hart) is supplied by Southern Water in the Hart Central zone and scores 8.3 out of 10, against an England and Wales average of 9.0. None of the 10 tested substances came close to a limit. The latest sample is from 24 August 2026.
- Iron is the reading closest to its limit, at 65% of the 0.2 mg/L maximumIt passed with room to spare, and everything else tested sat further below its limit. See every reading
- 2nd cleanest of 6 areas tested in HartOnly 1 area in Hart scored higher. The best is RG29 on 9.3.
- 0.7 points below the national average of 9Below the typical tested district in the UK, which is worth knowing before you choose a filter. Compare every area
Questions about GU17 water
Is GU17 tap water safe to drink?
Based on the latest tests, GU17 (Hart) water scores 8.3/10, which is safe. 0 of 10 tested contaminants exceeded recommended levels. Water is supplied by Southern Water.
What contaminants are in GU17 water?
We tested 10 contaminants in GU17 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 GU17?
GU17 (Hart) is supplied by Southern Water. You can view their full profile and compliance data on our supplier page.
Is GU17 water hard or soft?
No hardness reading has been published for GU17 itself. Across the GU postcode area the typical value is 154 mg/L CaCO3, which is classified as moderately hard. This is a moderate hardness level.
Should I use a water filter in GU17?
GU17 water scored 8.3/10 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 GU17 water?
The tap-water tests we hold for GU17 do not include a PFAS result. Environment Agency monitoring found PFAS in 40 river and groundwater samples from 1 sites within 10 km of GU17, the highest being PFPeA at 0.0061 µg/L about 9.7 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 GU17?
The Environment Agency rated the Blackwater (Hawley to Whitewater confluence at Bramshill) as moderate for ecological health in its 2025 assessment, meaning the river is noticeably changed by pollution or engineering. It is held back by water plants and algae and phosphate. 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 GU17, 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
- Is UK Tap Water Safe?Everything you need to know about tap water safety in the UK
- Best Water Filters UKEvery filter type compared on what it actually removes
PFAS explainedHow to test your waterBest water filtersFilter shower headsWater testing kitsUK water rankingsWater hardness checkerWater hardness map
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