How we investigate

Resolving complaints, disputes and company failures is an important part of our work because it enables us to effectively target the most serious harm and detriment to customers.

We carry out a range of different investigations and enforcement activity, from large and complex investigations into alleged breaches of competition law to smaller issues affecting individuals. We call this ‘casework’.

We focus on case work where our intervention could:

  • reduce a significant occurrence of customer harm or detriment; or
  • set a precedent that could encourage beneficial changes to the sector, such as encouraging competition; or
  • set a precedent that prevents similar cases in the future by, for example, encouraging water companies to change how they treat customers in future.

We call these types of intervention ‘strategic cases’.

We only intervene when we are best placed to do so. Our interventions are proportionate, timely and based on evidence. Where possible, we try to minimise the resources we use on non-strategic cases , which could be resolved by other means.

How we decide different types of cases


If two water companies merge (come under common ownership or control), then there is a risk that our ability to compare the performance of companies will be reduced. So, there is a special merger regime in the water sector which takes place in two phases.


If we become aware that a water company is in breach of its obligations, we may consider taking enforcement action. We have statutory enforcement powers under the Water Industry Act 1991 and concurrent powers under the Competition Act 1998 and Articles 81 and 82 of the EC treaty.

Director of Enforcement, Sally Irgin explains our approach to enforcement investigations in the video below.

Bulk supply pricing

Under sections 40 and 40A of the Water Industry Act 1991, we may make determinations on bulk supply agreements.

Transfer of private sewers

The Government introduced provisions to transfer the ownership of most private sewers and lateral drains to regulated sewerage companies in England and Wales. We are responsible for deciding on appeals against transfers.

Sewer flooding

Section 94 of the Water Industry Act 1991 places a duty on sewerage companies to maintain their sewers to ensure that their area is effectually drained. If we consider that a company may be in breach of its section 94 duties, we can take enforcement action.

Competition Act 1998 (CA98)

Along with the Competition & Market Authority (CMA) we concurrently enforce and apply the Competition Act 1998 (CA98). This prohibits conduct, agreements and business practices that damage competition in the United Kingdom.