About 1200 Napier residents are being asked to stop flushing toilets this evening because of a suspected broken wastewater pipe.
The pipe is under Kennedy Rd, one of the city's main arterial routes.
Households in the suburb of Pirimai are being asked to reserve water use.
Napier City Council asked residents to refrain from flushing toilets, using dishwashers and washing machines, and emptying baths until further notice.
Kennedy Rd, between Bill Herock St and Downing Ave, is closed and there is a detour in place.
The council's water team will be working onsite through the night to fix the damage.
Works are expected to be completed by tomorrow morning.