THE A4077 Crickhowell Road at Gilwern is expected to remain closed until May while Dwr Cymru carries out essential works.
Reasonable access for properties on the stretch of road will be maintained.
The temporary closure covers a 145m stretch of the road from the junction of Crickhowell Road and Glangrwyney Road in a north-westerly direction.
A signed diversion via the A4077, A465 and A40 and vice versa is in place.