The spokesperson went on to say all the water discharged had been treated to a high standard.
"We remove bacteria and viruses from our wastewater by using a milliscreen, aeration basins, clarifiers and ultraviolet (UV) light before returning it to our waterways."
Days Bay Beach is more than 400m from where the water was discharged, but Wellington Water is still testing the water to make sure it's safe.
"When we have done this previously, there has only been minor impact on the water quality 30m from the valve. Based on this, we don't believe there is any public health impact. As always, we have taken samples and are waiting for the results."