The utility company was alerted to a leak near Passage Lane car park on Saturday, which is close to a Site of Special Scientific Interest and shellfish waters linked to the River Hamble.
The burst is believed to have been discovered when footpaths near the pay and display parking spot were flooded.
While a social media post from Paul Holmes MP on Sunday confirmed that the spill had been stopped, Southern Water confirmed to the Echo that engineers are still on site today.
A spokesperson from the Environment Agency told the BBC that there was “no indication” bathing water had been affected.
READ MORE: Swanwick road set for temporary closure
Tankers are still on site at the parking spot near the River Hamble to manage the flow of water.
Mr Holmes’ social media post said that Southern Water were taking a “number of mitigation actions to protect the environment”.
This included having environmental specialists take samples and the use of barriers to stop overland flows.
A spokesperson from Southern Water told the Echo: “Our teams are repairing a burst sewer main near Passage Lane car park in Warsash.
“We currently have tankers on site to help manage the flow.
“We’re sorry for any disruption this is causing customers in the area.”
