Severe traffic disruption is expected in central London while a 17-month project is carried out to replace a Victorian water mains system.
Thames Water is undertaking the £6m project, which starts in Shaftesbury Avenue on 5 March and is scheduled to finish at the end of July 2008.
It is part of a larger programme of work throughout the whole of the West End, expected to last until 2010.
The Soho works will affect the W1D, W1F and WC2H postcode areas.
Thames Water's project manager Rob Archer said: "Tackling leakage is our biggest priority and since 2002, we have been working to replace the ageing water mains in London which are responsible for much of the problem.
"So far we have replaced 400 miles of pipes, enough to stretch from the capital to Aberdeen.
"Soho has some of the oldest, leakiest and most burst-prone pipes in the area.
"We will be replacing the cast-iron mains with new plastic ones, which are more durable and flexible.
"We appreciate that work on this scale will inevitably cause some disruption and inconvenience, but the benefits will be felt for years to come and we don't expect to have to return to deal with burst pipes or leaking mains in the future."
"We will minimise disruption, where possible, by using the latest construction techniques which in many places will avoid the need to dig long trenches."
Two-way traffic will be maintained for most of the work.
Excavations will start by the Palace Theatre and then continue west.
Bus routes 14, 19, 38, N38 and N19 will be affected.