South West starts ‘ice-pigging’ to rid pipes of parasites

South West Water has begun “aggressively” cleaning pipes with slushed ice where traces of cryptosporidium were detected.

The parasite was found in the water supply in Devon more than two weeks ago, with thousands of people still having to boil their water before using it.

A boil notice has been in place since 15 May. It originally affected around 40,000 people but now covers 2,500 homes.

The ice-pigging process involves an ice solution being injected into an isolated section of pipe and the valves re-opened to compact and drive the ice through the pipe to remove any sediment as it goes through.

The ice is then flushed out and further sampling is undertaken before the water supply can be restored.

Incident director at South West David Harris said progress is being made by “aggressively cleaning every surface” using the ice-pigging technique.

Since the incident occurred on 15 May, the company has cleaned its service reservoirs and flushed the network several times in an attempt to remove the remaining traces of cryptosporidium. The parasite poses a challenge to water treatment, because of its small size and resistance to chlorine.

Harris said: “Our water quality samples are showing progress, however, further intense work is needed to fully remove any contamination.”

He said ice-pigging would be a quicker more efficient method for the type of pipe than traditional methods.

It allows the company to clear the pipes without excavation, which minimises disruption and uses 50% less water used compared to other solutions.

South West said the technique can be 1,000 times more effective than flushing alone. It will combine ice-pigging with other solutions to remove traces of cryptosporidium.

Harris added: “Our teams continue to work around the clock to clean the network and to put interventions in place to prevent this from happening again. Our top priority is to return supply to the quality our customer expect and deserve, quickly and safely.”

Following the ice-pigging, Harris said the company’s water quality scientists will take detailed testing process that includes filtering water through special filters designed to capture any oocysts of the parasite.

More than 100 people in the Brixham area of Devon reported symptoms to their GP linked to drinking contaminated water and 22 cases of cryptosporidium were confirmed. A boil notice has remained in place for more than two weeks while work is being carried out. The company increased compensation for affected households to £265.

The parasite is understood to have entered the water supply when an air valve on pipes running under private land was damager, which South West is investigating the cause of.

The Drinking Water Inspectorate (DWI) is running an independent investigation into the causes of the incident. A 2021 report by the DWI said: “The prevalence of cryptosporidium in livestock makes it likely that most oocysts in the environment derive from agricultural sources.”