The earlier post said the system had been "overloaded", and added: "If we all work
together to reduce the amount of wastewater we're producing, we hope to avoid an emergency discharge into the estuary.
"We're asking all of Napier to please keep their household wastewater load as low as possible for the next 24 hours," it continued.
"That means letting your yellow mellow (eeek!), short showers and not running washing machine or dishwasher cycles.
"Don't rush to flush and we'll keep you updated on progress throughout the day," the council advised.
Toilets, showers, dishwashers and washing machines all drain into the city's wastewater network, which is also affected by infiltration of stormwater.
The council said in a media statement: "If an emergency discharge is carried out, this should prevent wastewater backing up and overflowing into city streets and properties."
The last time such a discharge happened was during the peak of four days of rain in the first week of September last year, and Kirton said the city now had warnings being issued after what he believed was a "modest" event in comparison.
"We just can't go on like this, and we need to have some decisions made," he said.
"This is deja vu, we were talking like this after the last election three years ago, but nothing's happened."
New Napier Mayor Kirsten Wise was not immediately available to comment.
In recent campaigning she put stopping discharges into the estuary and restoring the city to a guaranteed clean water supply at the top of her priorities.