Hundreds of water workers in Lancashire will join a two-day strike on Friday in protest over changes to their company pension scheme.
Staff who repair pipes, treat waste water and resolve customer queries will take action for the first time in 25 years over plans by United Utilities which they claim could cost some staff up to £10,000 a year in retirement income.
United Utilities, which supplies water to the North West, says only around one third of staff will be taking part in the strike on Friday and Monday.
The union Unison says the walkout will impact the whole of the region.
But the company has pledged that it will keep its service “running as normal.”
The changes in the pension scheme will come into force on April 1.
United Utilities paid out around £25m to consumers following the cryptosporidium contamination which affected 300,000 households and businesses across Lancashire in 2015.