Reversing water flow with Welsh Water

Owned by Glas Cymru, Welsh Water is a not-for-profit company and is the sixth largest of the ten regulated water and sewerage companies in England and Wales.
Welsh Water are responsible for providing over three million people with a continuous, high quality supply of drinking water and for taking away, treating and properly disposing of wastewater.
The mission
A reservoir was being taken out of service and in order to do this, reversing the water flow was required. Challenges associated with reversed water flow can affect the customer’s water colour and Ice Pigging was so successful that out of the 9,000 potentially affected customers, there was minimal customer disruption.

Key requirements

  • Minimise customer disruption
  • Remove sediment build up
  • Improve tap water quality
Our solution
Ice Pigging was chosen to clean 2.5km of a cement lined ductile iron pipe that provides water to 9,000 customers of Mynydd Llandygai and surrounding areas in North Wales. The pipe was cleaned over two nights with the main isolated for only 6 hours in total, resulting in no customer disruption and over 323kg of material removed from the two sections. Ice Pigging has allowed the company to reverse flows in a pipe which previously, would have been impossible at such short notice.
The results
  • Over 323kg of material removed from two sections
  • Water flows reversed with zero customer disruption
  • Pipe outage for only six hours


  • Only two times the pipe volume of water was used throughout the entire process
  • Minimal enabling works required and no excavations
  • No post cleaning disinfection was required and mains were directly returned to service