Scottish Water is in the hunt for four contractors under a 12-year framework deal worth up to £624m.
The quality and standards IV capital investment programme has been split into two lots: one for civil engineering, worth between £9m and £12m a year, and one for mechanical and electrical, valued at between £30m and £40m a year.
The programme will start next year, with both lots totalling up to £624m.
Scottish Water is looking for two tier one contractors per lot, with between five and eight contractors invited to tender for each lot.
Expressions of interest must be sent to the Public Contracts Scotland website by 4 July 2014.
In March, Scottish Water sought contractors to join a £100m framework to provide civil engineering and water mains replacement and rehabilitation.