An emergency evacuation of Dubbo's biggest swimming pool on a busy public holiday was caused by a "faecal contamination", Dubbo Regional Council has confirmed.
All the water in the pool - about 2.5 million litres - was conserved on Monday, the council's chief executive officer Michael McMahon said.
"NSW Health has a recommended protocol for an incident like this," he said.
"The 50-metre pool was only closed for about an hour... staff undertook a spot clean with the pool vacuum, before carrying out water testing to ensure the disinfection process is continuing.
"A backwash of the filters is also required and that process is under way today [Tuesday]."
Mr McMahon said council kept written records of water testing, backwashing and pool contamination treatments to ensure NSW Health requirements were met.
"Safety of pool patrons is of paramount importance to council and health authorities, which is why the pool was evacuated," he said.