Closure of Chawton Park Road could last up to eight weeks as South East Water lays new pipes to cope with demand caused by building many new houses in Alton.
This £166,000 project began on April 22 and is seeing 200 yards of new pipes laid under Chawton Park Road.
Chawton Park Road has been closed for safety reasons between Beechwood Road and Connaught Way, with a diversion along the A31.
The two-mile detour via the Chawton roundabout and a narrow railway bridge is affecting residents plus users of Alton Community Hospital, Alton Sports Centre, and the local Guides and Scouts huts.
South East Water project manager Jeremy Dufour said: “With new development in the area, we need to reinforce our network to maintain supplies now and in the future.
“We know there may be some disruption for residents and businesses locally and we apologise for this, but please be assured we will work to try to finish sooner.”