Work to protect drinking water supplies in part of East Sussex is taking place.
The scheme is to prevent the disruption of emergency repairs
South East Water is replacing a section of water mains "in poor condition and increasingly prone to bursts" to avoid the disruption of emergency work.
The pipe, at Piddinghoe, takes water from an underground supply to a storage reservoir that serves about 30,000 people in Newhaven and Peacehaven.
The £300,000 improvement scheme was getting started in mid-March and would take about 12 weeks, the company said.
South East Water said a specialist drilling machine would be used which would allow the water pipe to be laid without the need for open excavations.
The pipe, which passes across a flood plain, underneath the railway line and the River Ouse, was originally laid in the 1970s.
The company said water supplies would be maintained while work is carried out by using other parts of the supply network.
It comes as the South East faces its most serious drought in the last 100 years, after two consecutive winters with below-average rainfall.