The project is part of Scottish Water’s £2.1m programme which started in Inverclyde in March. Improvements will start on 10 July and will take up to a month to complete.

Drew McKenzie, chairman of Port Glasgow Traders’ Association, attended a meeting at Port town hall with Scottish Water chiefs to discuss the work.

He told the Telegraph: “We’re aware that parts of the road will need to close but the car park in Princes Street will stay open.

“I discussed it with traders at a meeting and they are quite philosphical about it.

“It starts during the Greenock Fair so it might not be as bad as at other times.

“It’s all about letting the businesses know when the work is taking place and Scottish Water seem to be doing that very well, all credit to them.

“A representative has made contact with every business and church to explain the situation, they’ve been very pro-active.” Water bosses hope to keep disruption to a minimum but there will be some planned temporary shutdowns to the supply.

A section of Church Street between Princes Street and King Street will be closed during part of the town centre work.

Traffic management measures will also be put in place, including the reversal of the flow to the one-way traffic system along Princes Street from John Wood Street to Wilson’s Lane.

Port Glasgow councillor Jim MacLeod, who was also at the briefing meeting, said: “The upgrading of water mains is obviously very important because the mains provide an essential service to us all. It is vital that we have good clean drinking water and that this investment takes place.

“This sort of investment cannot be carried out without some temporary disruption and I would ask that all affected people in the community and local businesses try and keep this in mind.

“Scottish Water have assured me that they will keep any disruption to a minimum, ensure good access for everyone is maintained for goods and services and that they will have dialogue with local traders and residents in advance of the works.” The public reassurance follows stinging criticism of Scottish Water over traffic chaos which lasted for seven weeks during part of the upgrade at the A8 which finished last month.

Joanna Peebles, Scottish Water’s regional communities team manager, said: “We would stress that any short-term inconvenience during our improvement work will be far out-weighed by the long-term benefits it will deliver – clearer, fresher drinking water for people across the area for many years to come.”