The network gradually expanded to cover an area mostly north of the Thames from Hyde Park in the west to Docklands in the east.

[1] The pressure was maintained at a nominal 800 pounds per square inch (5.5 MPa) (55 BAR) by five hydraulic power stations, originally driven by coal-fired steam engines.

[1] These were at: Short-term storage was provided by hydraulic accumulators, which were large vertical pistons loaded with heavy weights.

The company, as a UK statutory authority, had the legal right to dig up the public highways to install and maintain its pipe network.

This made it attractive to Mercury Communications (a subsidiary of Cable & Wireless) who bought the company and used the pipes as telecommunications ducts.