What is Thames Water's GWSS score?

Thames Water scores 62.7/100 on the Gera Water Service Score (GWSS) in 2024-25 — Average (grade C), ranking #14 of 19 UK water companies. The score combines leakage (143 l/p/d, weight 40%), supply interruptions (9 mins, weight 30%), and water quality CRI (2.04, weight 30%) from Ofwat APR 2024-25 and DWI data.

How much water does Thames Water leak?

Thames Water lost 143 litres of water per property per day through leaks in 2024-25, above the England and Wales average of 109 l/p/d. Source: Ofwat Annual Performance Report 2024-25, via DiscoverWater.co.uk (OGL v3.0).

How often does Thames Water cause supply interruptions?

In 2024-25, Thames Water customers experienced an average of 00:09:35 of lost water supply per property from interruptions lasting 3+ hours — better than the national average of 22 mins. Source: Ofwat APR 2024-25 via DiscoverWater.co.uk.

What is Thames Water's Compliance Risk Index (CRI)?

Thames Water's CRI in 2024 was 2.04, below the England and Wales average of 3.72. The CRI measures overall performance against national drinking water quality standards (lower = fewer compliance failures). Source: Drinking Water Inspectorate (DWI), Jan–Dec 2024, via DiscoverWater.co.uk.

How has Thames Water's water quality changed over the past 4 years?

Thames Water's CRI (Compliance Risk Index) over the past 4 years: 2024: 2.04, 2023: 10.96, 2022: 1.43, 2021: 2.04. Lower CRI = fewer quality compliance failures. Source: Drinking Water Inspectorate (DWI), via DiscoverWater.co.uk.

GeraMarket / UK water company performance / Thames Water

Thames Water: Performance Report

Rank #14 of 19 UK water companies · GWSS 62.7/100 (Average) · Leakage 143 l/p/d · Interruptions 00:09:35/property · CRI 2.04 (Ofwat APR 2024-25 / DWI 2024)

How does Thames Water perform compared to other UK water companies?

In Ofwat APR 2024-25 / DWI 2024, Thames Water ranks #14 of 19 UK water companies with a Gera Water Service Score (GWSS) of 62.7/100 — Average, 8.1 points below the national median of 70.8/100. Key metrics: leakage 143 l/p/d, supply interruptions 00:09:35/property, Compliance Risk Index 2.04 (Ofwat APR / DWI 2024, OGL v3.0).

Source:Ofwat APR 2024-25 + DWI CRI 2024 (via DiscoverWater.co.uk)·as of Ofwat APR 2024-25 / DWI 2024updated annually (last: 20 June 2026)

Gera Water Service Score62.7 / 100Thames Water — Average (grade C) · #14 of 19 UK water companies · Ofwat APR 2024-25 / DWI 2024How this index is calculated

Reference period: Ofwat APR 2024-25 / DWI 2024· Ofwat APR 2024-25 + DWI CRI 2024 · Open Government Licence v3.0 · London & South

Leakage score

25/100

143 l/p/d

E&W avg: 109

▲ above avg · weight 40%

Interruptions score

94.3/100

00:09:35

E&W avg: 22 mins

▼ below avg · weight 30%

Water quality score

81.3/100

CRI 2.04

E&W avg: 3.72

▼ below avg · weight 30%

Thames Water performance figures (Ofwat APR 2024-25 / DWI 2024)

Thames Water — Ofwat APR 2024-25 + DWI CRI 2024
Measure	Value	vs England & Wales
Gera Water Service Score (GWSS)	62.7/100	Average (grade C)
Overall rank	#14 of 19	vs national median GWSS 70.8/100
Leakage	143 l/p/d	▲ above E&W avg 109 l/p/d
Supply interruptions	00:09:35	▼ below E&W avg 22 mins
CRI (water quality)	2.04	▼ below E&W avg CRI 3.72
Region	London & South	Ofwat regulatory area

Thames Water CRI trend (2021–2024)

Compliance Risk Index (lower = better). Source: Drinking Water Inspectorate (DWI) via DiscoverWater.co.uk.

Year	CRI	vs E&W avg (3.72)
2024	2.04	▼ below avg
2023	10.96	▲ above avg
2022	1.43	▼ below avg
2021	2.04	▼ below avg

Compare Thames Water with other water companies

Sort by GWSS, leakage, interruptions, or water quality to see how your company compares across all metrics.

Thames WaterGWSS 62.7/100 · leakage 143 l/p/d · interruptions 00:09:35 · CRI 2.04

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Overall GWSS (highest first)

Company	GWSS	Leakage	Interruptions	CRI	Grade
#1SES Water	93.2/100	68 l/p/d	00:26:40	0.00	A
#2Bristol Water	89.7/100	68 l/p/d	00:06:49	2.84	A
#3Portsmouth Water	88.9/100	90 l/p/d	00:02:01	0.45	A
#4Anglian Water	87.1/100	80 l/p/d	00:06:51	2.11	A
#5Affinity Water	84/100	95 l/p/d	00:03:21	1.44	B
#6South West Water	79.5/100	102 l/p/d	00:14:44	1.19	B
#7Wessex Water	77.9/100	108 l/p/d	00:10:00	1.31	B
#8South East Water	75.8/100	96 l/p/d	00:44:06	1.09	B
#9Cambridge Water	73.1/100	80 l/p/d	00:15:04	6.58	B
#10Yorkshire Water	70.8/100	111 l/p/d	00:08:27	3.61	B
#11Essex and Suffolk Water	69.4/100	64 l/p/d	00:04:40	10.94	C
#12South Staffs Water	64.3/100	103 l/p/d	00:15:04	6.58	C
#13Hafren Dyfrdwy	64.2/100	145 l/p/d	00:11:11	1.10	C
#14Thames Water	62.7/100	143 l/p/d	00:09:35	2.04	C
Leakage score 25/100 143 litres/property/day Interruptions score 94.3/100 00:09:35 per property Water quality score 81.3/100 CRI 2.04 CRI history (2021–2024, lower = better): 2024: 2.04 2023: 10.96 2022: 1.43 2021: 2.04 Full Thames Water report →
#15Severn Trent Water	58.2/100	98 l/p/d	00:04:34	10.32	C
#16Northumbrian Water	58/100	94 l/p/d	00:04:40	10.94	C
#17Southern Water	50/100	89 l/p/d	02:21:50	3.82	D
#18United Utilities	48.2/100	119 l/p/d	00:14:17	10.28	D
#19Dŵr Cymru Welsh Water	19.4/100	169 l/p/d	02:17:44	4.18	E

Showing 19 of 19 UK water companies. Source: Ofwat APR 2024-25 + DWI CRI 2024, via DiscoverWater.co.uk (OGL v3.0).

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Frequently asked questions

What is Thames Water's GWSS score?: Thames Water scores 62.7/100 on the Gera Water Service Score (GWSS) in 2024-25 — Average (grade C), ranking #14 of 19 UK water companies. The score combines leakage (143 l/p/d, weight 40%), supply interruptions (9 mins, weight 30%), and water quality CRI (2.04, weight 30%) from Ofwat APR 2024-25 and DWI data.
How much water does Thames Water leak?: Thames Water lost 143 litres of water per property per day through leaks in 2024-25, above the England and Wales average of 109 l/p/d. Source: Ofwat Annual Performance Report 2024-25, via DiscoverWater.co.uk (OGL v3.0).
How often does Thames Water cause supply interruptions?: In 2024-25, Thames Water customers experienced an average of 00:09:35 of lost water supply per property from interruptions lasting 3+ hours — better than the national average of 22 mins. Source: Ofwat APR 2024-25 via DiscoverWater.co.uk.
What is Thames Water's Compliance Risk Index (CRI)?: Thames Water's CRI in 2024 was 2.04, below the England and Wales average of 3.72. The CRI measures overall performance against national drinking water quality standards (lower = fewer compliance failures). Source: Drinking Water Inspectorate (DWI), Jan–Dec 2024, via DiscoverWater.co.uk.
How has Thames Water's water quality changed over the past 4 years?: Thames Water's CRI (Compliance Risk Index) over the past 4 years: 2024: 2.04, 2023: 10.96, 2022: 1.43, 2021: 2.04. Lower CRI = fewer quality compliance failures. Source: Drinking Water Inspectorate (DWI), via DiscoverWater.co.uk.

Contains public sector information published by Ofwat / Drinking Water Inspectorate and licensed under the Open Government Licence v3.0. Source: Ofwat APR 2024-25 + DWI CRI 2024 (via DiscoverWater.co.uk) (Ofwat APR 2024-25 / DWI 2024, published June 2026 (Ofwat APR 2024-25)).