WD18 tap water: what's in it?
Affinity Water: at least 20 tests failed UK drinking-water standards in 2025 (DWI, company-wide).
Some published DWI figures don't reconcile or identify a company, so we've left them out; the true number may be higher. England overall: 99.97% of tests met standards.
WD18 tap water quality report · 2026
Hardness
Very hard
Watford South (supply zone) · read on 29 September 2026
Details
Watford South (supply zone) · read on 29 September 2026
Hosepipe ban
In force in part of Affinity Water's area
A ban has been reported, but the notice doesn't confirm which parts of the supply area it covers. Check with your water company before using a hosepipe. Checked 11 October 2026 at 02:34
Details
A ban has been reported, but the notice doesn't confirm which parts of the supply area it covers. Check with your water company before using a hosepipe. Checked 11 October 2026 at 02:34
Storm overflows
7 overflows within 10 km of WD18 centre
53 spills in 2025
Details
53 spills in 2025
Lead pipes
53% built before 1973
Estimate, not a test. Homes in the parts of WD18 we can match to council-tax records (100% of its postcodes) whose build period is known; the share with no recorded build period isn't published for these areas. Allowing for suppressed counts: 52–54%. England and Wales: 61% (2026).
Details
Estimate, not a test. Homes in the parts of WD18 we can match to council-tax records (100% of its postcodes) whose build period is known; the share with no recorded build period isn't published for these areas. Allowing for suppressed counts: 52–54%. England and Wales: 61% (2026).
Who supplies water in WD18
Supplies 719 of 719 postcodes (100%)
Affinity Water's phone number isn't in our records; their contact page lists it.
We can't tell your sewerage company from official data for this area. It's named on your water bill.
Drinking-water test record
Affinity Water: 719 of 719 postcodes
Affinity Water
Affinity Water, company-wide
- Regulator
- DWI
- Report year
- 2025
- Failed tests
- Not shown
- Tests
- 189,963
The regulator's published total and its company rows disagree, so we don't show a count.
| Parameter | Failed tests |
|---|---|
| E. coli (confirmed) | Failed tests: 4 |
| Enterococci (confirmed) | Failed tests: 2 |
| Iron | Failed tests: 1 |
| Lead | Failed tests: 6 |
| Nickel | Failed tests: 3 |
| Total coliforms (confirmed) | Failed tests: 4 |
Source: DWI england 2025, Annex B — dated 6 July 2026, read 13 October 2026
Source: DWI england 2025, Annex A — dated 6 July 2026, read 13 October 2026
England: 99.97% of tests met standards in 2025 (DWI).
Source: DWI england 2025, national compliance — dated 6 July 2026, read 13 October 2026
How hard is the water in WD18?
91% of WD18's postcodes are in the Watford South supply zone (Affinity Water): 351 mg/l, very hard.
Watford South · Affinity Water (655 of 719 postcodes)
351 mg/l · 24.6 °Clark · 19.7 °dH · 35.1 °fH
From the company's postcode lookup.
Watford South (supply zone) · read on 29 September 2026
Source: Affinity Water — read 29 September 2026
4 identified supply zones in WD18
Watford South · Affinity Water (655 of 719 postcodes)
351 mg/l · 24.6 °Clark · 19.7 °dH · 35.1 °fH
From the company's postcode lookup.
Watford South (supply zone) · read on 29 September 2026
Source: Affinity Water — read 29 September 2026
Northwood · Affinity Water (47 of 719 postcodes)
348 mg/l · 24.4 °Clark · 19.5 °dH · 34.8 °fH
Zone average.
Northwood (supply zone) · 1 January 2025 to 31 December 2025
Source: Affinity Water — dated 1 January 2025 to 31 December 2025, read 29 September 2026
Watford North · Affinity Water (15 of 719 postcodes)
323 mg/l · 22.7 °Clark · 18.1 °dH · 32.3 °fH
Zone average.
Watford North (supply zone) · 1 January 2025 to 31 December 2025
Source: Affinity Water — dated 1 January 2025 to 31 December 2025, read 29 September 2026
Rickmansworth/Gerrards Cross · Affinity Water (2 of 719 postcodes)
282 mg/l · 19.8 °Clark · 15.8 °dH · 28.2 °fH
From the company's postcode lookup.
Rickmansworth/Gerrards Cross (supply zone) · read on 29 September 2026
Source: Affinity Water — read 29 September 2026
Storm overflows nearby
7 overflows within 10 km of WD18 centre · 53 spills in 2025
WD18 (district) · 2025
Source: Environment Agency EDM annual return 2025 — dated 20 August 2026, read 13 October 2026
Overflows here are run by Thames Water.
3 of these were monitored for only part of 2025.
Nearest 5 shown
15 Coldharbour Lane, Bushey
Into Colne Brook · 4.1 km from the centre of WD18
0 spills · 0 hours · Monitored 100% of 2025
MAPLE LODGE STW, BUCKS
Into RIVER COLNE · 6.5 km from the centre of WD18
35 spills · 454.5 hours · Monitored 99.9% of 2025
N/A
Into Not Applicable · 8.7 km from the centre of WD18
0 spills · 0 hours · Monitored 95.6% of 2025
N/A
Into Not Applicable · 9 km from the centre of WD18
0 spills · 0 hours · Monitored 100% of 2025
CSO AT DAINTRY ROAD
Into WEALDSTONE BROOK · 9.2 km from the centre of WD18
6 spills · 7.8 hours · Monitored 100% of 2025
Annual 2025 figures from monitored overflows. Not live, and not a bathing-water or tap-water verdict.
- 57 England outfalls in the 2025 return had no usable location and aren't counted.
- Northern Ireland isn't covered: No licensed annual per-outfall source in the approved source list; BT postcode coordinates require an LPS licence.
Older homes and lead pipes
53% built before 1973
53% of homes here were built before 1973 — estimate, not a test.
Homes in the parts of WD18 we can match to council-tax records (100% of its postcodes) whose build period is known; the share with no recorded build period isn't published for these areas. Allowing for suppressed counts: 52–54%. England and Wales: 61% (2026).
Older homes are more likely to have lead pipes. Only a test tells you whether yours does.
WD18 (district) · 2026
Source: Valuation Office Agency, Council Tax: stock of properties — dated 31 March 2026, read 24 September 2026
Fluoride
We cannot confirm whether this area is part of a water fluoridation scheme. Ask your water supplier using your postcode.
Around one in ten people in England receive drinking water supplied by a fluoridation scheme.
England · 2026 health monitoring report
Source: UKHSA and DHSC — dated 30 March 2026, read 13 October 2026
Hosepipe bans
What you can do
As an Amazon Associate we earn from qualifying purchases. Links go to amazon.com; Amazon's Earn Globally service can localise them to amazon.co.uk. Check the model and UK delivery before buying.
Water filter jugs
LifeStraw
LSH7GLSPK21
Performance certification:
Certified by WQA to NSF/ANSI 42 for Aesthetic Chlorine and Taste and Odor; Certified by WQA to NSF/ANSI 53 for Lead and Mercury; Certified by WQA to NSF/ANSI 401 for Microplastics (a US/international standard; it is not UK approval)
View Detailsreduces chlorine taste and odour in drinking water.
A UK retailer lists this model. Amazon UK stock and delivery are unverified; this Amazon link may not ship to the UK. Check the exact model and UK delivery before you pay.
UK availability evidence checked 14 October 2026.
Shower filters
Weddell Water
WD-100BL
Performance certification:
Certified by NSF to NSF/ANSI 177 for Free Available Chlorine Reduction (a US/international standard; it is not UK approval)
View Detailsreduces chlorine in shower water; does not soften water.
A UK retailer lists this model. Amazon UK stock and delivery are unverified; this Amazon link may not ship to the UK. Check the exact model and UK delivery before you pay.
Check it fits your shower fitting before buying; a US fitting may need an adaptor.
UK availability evidence checked 14 October 2026.
We haven't verified a water softener for UK buyers yet.
What a pick has to pass:
- An exact-model listing from NSF, WQA or IAPMO for the model sold in the UK
- Listed to NSF/ANSI 44, the water softener standard
- The manufacturer's documented feed connection and water-pressure range, so a plumber can check them against UK pipework
- UK availability evidenced by Amazon UK, the manufacturer or a UK retailer, checked in the last 90 days
Until we can recommend one, see what a softener costs to buy, fit and run in the UK. Water softener cost
We haven't verified a lead test kit for UK buyers yet.
What a pick has to pass:
- A lead result reported by a laboratory accredited for that test (UKAS, ISO/IEC 17025), named on the kit's listing
- UK availability evidenced by Amazon UK, the manufacturer or a UK retailer, checked in the last 90 days
Start with your water company: if you think you have lead pipes, you can ask it to test the water at your kitchen tap. Which water test you need
Common water problems
How much does a water softener cost in the UK?
Water softener cost UK 2026: price by home size
Why is my tap water cloudy or white?
Why is my tap water cloudy or white? (UK)
Brown tap water: causes and what to do (UK)
Why does my tap water taste metallic?
Tap water tastes metallic? Causes and fixes (UK)
Questions about tap water in WD18
- Is the water in WD18 hard or soft?
- Affinity Water: very hard, 351 mg/l, 24.6 °Clark, 19.7 °dH, 35.1 °fH (Watford South (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: very hard, 348 mg/l, 24.4 °Clark, 19.5 °dH, 34.8 °fH (Northwood (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: very hard, 323 mg/l, 22.7 °Clark, 18.1 °dH, 32.3 °fH (Watford North (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: hard, 282 mg/l, 19.8 °Clark, 15.8 °dH, 28.2 °fH (Rickmansworth/Gerrards Cross (supply zone), read on 29 September 2026). From the company's postcode lookup.
- What does the drinking water regulator's record show for WD18?
- Affinity Water: at least 20 tests failed UK drinking-water standards in 2025 (DWI, company-wide). Some published DWI figures don't reconcile or identify a company, so we've left them out; the true number may be higher. England overall: 99.97% of tests met standards.
- Could homes in WD18 have lead pipes?
- 53% of homes here were built before 1973 — estimate, not a test. Homes in the parts of WD18 we can match to council-tax records (100% of its postcodes) whose build period is known; the share with no recorded build period isn't published for these areas. Allowing for suppressed counts: 52–54%. England and Wales: 61% (2026). Older homes are more likely to have lead pipes. Only a test tells you whether yours does.
- Is the water in WD18 fluoridated?
- We cannot confirm whether this area is part of a water fluoridation scheme. Ask your water supplier using your postcode. Around one in ten people in England receive drinking water supplied by a fluoridation scheme.
Sources and method
- Water Company Boundaries (UC2) ↗ · 19 September 2026 · read 20 September 2026
- DWI england 2025, Annex B ↗ · 2025 · read 13 October 2026
- DWI england 2025, national compliance ↗ · 2025 · read 13 October 2026
- Affinity Water ↗ · read on 29 September 2026 · read 29 September 2026
- Affinity Water ↗ · 1 January 2025 to 31 December 2025 · read 29 September 2026
- Environment Agency EDM annual return 2025 ↗ · 2025 · read 13 October 2026
- Valuation Office Agency, Council Tax: stock of properties ↗ · 2026 · read 24 September 2026
- UKHSA and DHSC ↗ · 2026 health monitoring report · read 13 October 2026
- Environment Agency ↗ · 11 October 2026 · read 11 October 2026
Affinity Water, Affinity Water, Affinity Water, Affinity Water: Database right, used under the publisher's terms.
Water company boundaries © Water UK, licensed under CC BY 4.0Contains public sector information licensed under the Open Government Licence v3.0All content is available under the Open Government Licence v3.0, except where otherwise stated © Crown copyright
Data generation uk-2026-10-16-derive6