The Discolouration Challenge

Imagine you have just come home from work, run a bath and the water looks brown and mucky… You wouldn’t want to get in it, let alone make a cup of tea with it! You would be rather worried and would be straight on the phone to your local water supplier to complain. Unless you were me… I’d get rather excited because I’ve been researching and mitigating discolouration for the last 20 years, but have only experienced it a couple of times as a customer myself!

This unfortunate event is called ‘discolouration’ and is caused by the re-mobilisation of previously accumulated natural deposits of iron and manganese from the pipe walls during a high flow event, such as a mains burst or valving operation.

In the UK, we are very fortunate to have one of the highest standards of drinking water quality, and, although rare events for most, discolouration customer contacts are the largest proportion of water quality complaints received by UK water companies.

Managing discolouration is a major challenge for the UK water industry. The regulator imposes Outcome Delivery Incentives (ODIs), which have the potential for both large financial reward and penalty for performing under or over the contact target. In addition, finding the source of discolouration is very problematic, as the customer contact is only a record of where the material is observed and not where it originated. Events are often very short lived and resolved by the time the inspector arrives on site to investigate. Lastly, managing discolouration is an expensive business. One of the primary sources of discoloration material is the corrosion of ageing, unlined, cast iron pipes, and wide scale mains replacement or relining is a cost-prohibitive water infrastructure activity.

Water companies undertake large flushing programmes to remove the discolouration material, but experience diminishing returns in customer contact reduction as the number of flushed District Meter Areas (DMAs) increases. It can therefore be argued that there should be a sustainable level of discolouration, as the cost to drive down “ones and twos” or background levels of discolouration become prohibitive. Another thing to bear in mind is, once a flushing programme starts it can't be stopped, as the discolouration material constantly reaccumulates. In 18 months’ time you will be back to square one.

WRc Group now offers asset management, a discolouration investigation service to tackle the most difficult DMAs where water utilites have tried absolutely everything else. We will perform GIS and hydraulic studies, water sampling, turbidity monitoring, smart flushing, and CCTV work to pinpoint the cause of the discolouration complaints. The rogue asset could be as small as a corroded valve or a small unlined section of cast iron main in a difficult road junction, but we will find it!

Check out the CCTV video below where you can see discolouration material and tuberculation in an unlined, cast iron pipe and where it joins to a new pipe of preferred material, demonstrating our utility management capabilities.