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.

leakage2012

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 concers about being able to meet their target next year.

sosi2012

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

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

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
Blue means companies did not have to submit this data

*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 Porstmouth Water data.