Reliability and availability

Leakage

Customers care about levels of leakage. At the 2009 price review they identified it as their second most important issue behind affordable bills.

Reducing leakage is just one way companies can help balance supply and demand. It is part of a best value package including promoting efficient use of water, metering or developing new sources of raw water. Companies calculate the appropriate levels of leakage as part of the water resources management plans and take in to account social and environmental costs and benefits such as disruption to traffic or additional carbon emissions.

We challenge the companies to operate at the sustainable, economic level of leakage (SELL) by setting them annual leakage targets (shown in blue in the graph below). The SELL is set at the level where reducing leakage further is more expensive than balancing supply and demand through an alternative measure.

Companies have very different sustainable, economic levels of leakage. There are a combination of factors affecting the SELL including

the size and condition of the asset base
the predominant soil type of the region
operating pressures
the ratio of urban to rural populations
the pressures on water resources

Because of this we hold companies to account for their level of leakage compared to their own target and do not compare performance between companies.

Portsmouth Water have notified us that the level of leakage originally reported for 2011-12 was inaccurate. We are currently working with Portsmouth Water to understand the reasons for this. And so we have not included Portsmouth Water in the graph or data below.

Green means the company’s performance is in line with or better than expected
Amber means the company’s performance is not in line with expectations but performance has slipped only slightly
Red means the company’s performance is significantly below target or expectation

Security of supply

Each company has a duty to maintain the security of its water supplies. The security of supply index (SOSI) is used to assess each company’s compliance with this duty.

When calculating their index scores, companies make assumptions about the levels of service they expect to provide to their customers. They cover their expectations about the frequency and duration of restrictions on use, such as temporary restrictions on customers’ non-essential water usage, during dry years. Therefore the index takes into account that there may be restriction on water use at certain points in time during dry years. As a result it is possible for a water company to have a 100% security of supply index at the same time as requiring water restrictions such as hosepipe bans.

Each company calculates an index score where 100 is the maximum – a secure supply. A company can have a score of 100 but still have an amber rating if they have concerns about being able to meet their target next year.

Serviceability

Each company is required to maintain its assets to a defined standard so that it can provide reliable services to customers over the long term ‒ and protect the environment. We call this ‘stable serviceability’.

Serviceability is a regulatory tool that measures and confirms that capital maintenance outputs have been delivered for customers and the environment. Performance is measured through 20 indicators which are grouped into to four sub-services:

serviceability water non-infrastructure (for example water treatment works) (5 indicators)
serviceability water infrastructure (for example underground water mains) (6 indicators)
serviceability for sewerage non-infrastructure (for example sewerage treatment works) (3 indicators)
serviceability sewerage infrastructure ( for example underground networks sewers) (6 indicators)

Each company makes a judgement about the overall serviceability in each sub-service and updates the serviceability status as either improving, stable, marginal or deteriorating. We will make our own assessment of serviceability as part of the 2014 price review.

Data

	Serviceability water non-infrastructure	Serviceability water infrastructure	Serviceability for sewerage non-infrastructure	Serviceability sewerage infrastructure	Leakage (target in Ml/day)	Leakage (actual in Ml/day)	Security of supply index (SoSI)
Anglian	Stable	Stable	Stable	Marginal	212	199	100
Dŵr Cymru	Stable	Stable	Marginal	Stable	188	185	100
Northumbrian	Stable	Stable	Stable	Stable	147	130	100
Severn Trent	Stable	Marginal	Stable	Stable	474	464	99
South West	Stable	Stable	Stable	Stable	84	81	100
Southern	Stable	Stable	Stable	Stable	93	82	100
Thames	Stable	Stable	Stable	Stable	673	637	100
United Utilities	Stable	Stable	Improving	Marginal	464	453	100
Wessex	Stable	Stable	Stable	Stable	71	69	100
Yorkshire	Stable	Marginal	Stable	Stable	297	274	100
Affinity Water* (central)	Stable	Stable	—	—	185	158	100
Affinity Water* (east)	Stable	Stable	—	—	5.1	4	100
Affinity Water* (southeast)	Stable	Stable	—	—	7.8	7	100
Bristol	Stable	Stable	—	—	51	43	100
Cambridge	Stable	Stable	—	—	14	12	100
Dee Valley	Stable	Marginal	—	—	10.2	9	100
Portsmouth	Stable	Stable	—	—	**	**	100
Sembcorp Bournemouth	Stable	Stable	—	—	22	22	100
South East	Stable	Marginal	—	—	95	95	100
South Staffs	Stable	Stable	—	—	74	68	100
Sutton & East Surrey	Stable	Stable	—	—	25	24	100

*Formerly Veolia Water Central, Veolia Water East and Veolia Water Southeast.

**Portsmouth Water have notified us that the level of leakage originally reported for 2011-12 was inaccurate. We are currently working with Portsmouth Water to understand the reasons for this. And so we have not included Portsmouth Water data.