After passing through the turbines the steam has been reduced to a temperature rather below blood heat and is under conditions of very high vacuum. At this stage the steam has to be condensed to water in order that it can be re-used and pumped back into the boiler. The condensers, situated underneath each turbine, are kept cool by means of a supply of strained river water which is fed through many thousands of 1" diameter brass tubes inside the condenser shell before being led back to the river or to the Cooling towers. The steam condenses on the outside of these tubes and trickles down to the bottom of the condenser where it is collected together and started on its journey back to the boiler by the "extraction" pumps. In order to keep this condensing process working some 26,000,000 gallons of circulating water are required each hour when all the plant is in operation.

The River Trent cannot supply such a quantity as this at any time although, under favourable conditions, it can supply the 16,400,000 gallons per hour required by 'A' Station without difficulty. Cooling towers are provided, however, and are used in 'A' Station when river flow is insufficient for station requirements and at all times in Willington 'B' Power Station where a quantity of river water is kept flowing into the circulating water system in order to replace losses.

In order to meet the requirements of the Trent River Authority it is necessary that the temperature rise of the River, measured from a point upstream of the circulating water intakes to another point below the outfall pipes, must not exceed 8.5°C, and, in addition to this restriction, it is laid down that temperature of the river, measured at a point approximately 175 yards below the circulating water out-fall pipes, must not exceed 30°C. Plant operation must be regulated in such a way that these two conditions are complied with at all times.

Boiler make-up water is not taken from the river but is supplied by the South Staffordshire Water Board. This water is hard and, in order to prepare it for use in the boilers, there is a water treatment plant in each Power Station capable of treating 10,000 gallons of water per hour and making it suitable for use on the plant. A one million gallon "towns main" water reserve tank has been built in order to provide a buffer stock of water against the possibility of failure of the South Staffordshire Water Board system.