Unite, the GMB and Unison union members are taking part in action across Dumfries and Galloway on Tuesday and Wednesday this week.
Unison warned that emergency repairs and water quality checks would not be carried out and problems with supply or sewage would have to wait until the strike was over.
It said it had rejected a 2.6 per cent pay offer, saying it “fails to compensate staff for a decade of real-term pay cuts”, although Scottish Water said the current offer was higher.
Mr Smyth said: “The current cost of living crisis, following on the back of the terrible years of pandemic, have left many people struggling to make ends meet.
“No-one wants to go on strike but unless Scottish Water makes a meaningful pay deal, people have no choice.
“I have stood on many picket lines in solidarity with workers these past few years and I will continue to fully support those who feel they must go on strike.
“I would urge publicly owned Scottish Water to properly fund a deal and start paying staff a decent wage as that is the only action which will prevent more disruption.”
