Welsh Water has lifted the precautionary boil water notice issued to customers on Friday last week in parts of Rhondda Cynon Taf supplied by Maerdy Water Treatment Works with immediate effect.

On Thursday evening, a burst pipe affected the coagulant dosing process at Maerdy Water Treatment Works. This meant that, for a period of around 10 hours, water leaving the works did not go through the full treatment process before entering supply, because not enough of the coagulation chemical was added to the treatment process.

As soon as the issue was identified on Friday morning, the works was shut down, the fault was then repaired, and the treatment process was brought back online. Welsh Water issued the precautionary boil water advice while testing and network flushing continued. To allay any customer concerns, the water company has emphasised that this was NOT an issue with too much of a chemical being added to the treatment process.

The boil water notice is now being lifted for customers in three zones in a phased approach. The notice in Zone 1 has been lifted with immediate effect, meaning customers no longer need to boil tap water before drinking, cooking or brushing teeth.

Customers in the Zone 2 and 3 areas are advised to continue to boil tap water until further notice. Welsh Water currently aims to lift the boil water notice in Zone 2 at 6pm on Tuesday, 26 May and in Zone 3 at 6pm on Wednesday, 27 May. Customers can check whether they are affected by using the postcode checker on our website at dwrcymru.com.

The timings reflect the different positions of each area in the network and how long it takes for fully treated water to replace the water already in the system. If test results require, the utility will keep the notice in place longer, but Welsh Water’s current expectation is that these are the points at which each zone can be cleared safely.

Welsh Water Chief Operating Officer Steve Wilson said:

“We are adopting a phased approach to lifting the boil water notice so that restrictions can be removed as soon as it is safe to do so in each part of the network, rather than waiting for every area to clear at the same time.

“Water moves gradually through this network, largely by gravity, meaning some communities receive refreshed treated water sooner than others.

“Before lifting the notice in any zone, we are carrying out extensive sampling, testing and network flushing to ensure water quality meets the high standards our customers expect. Protecting public health has been our priority throughout this incident and we will continue to update customers as this phased process progresses.

“Our bottled water stations will remain open for as long as they are needed and we would like to thank customers for their continued patience and understanding. We recognise the significant disruption and inconvenience this incident has caused, particularly during the current period of hot weather, and we are sorry for the impact on customers and communities.”