Thousands of gallons of festering sewage was pumped into Paisley’s river - and turned swans brown.
The birds, which were feeding just downstream, lifted their necks out of the water and onlookers spotted the horrid colour change.
The disgusting discharge sent a pong across the heart of the town.
Human waste and loo roll were seen firing into the White Cart.
An emergency sewer underneath Abbey Bridge opened on Monday as a result of the Bank Holiday downpour.
But Dave Johnston, from Seedhill, is astonished the practice is still allowed to happen.
He said: “During a walk, I noticed copious amounts of raw sewage being discharged into the river from the outflow beneath the Abbey Bridge.
“I could actually smell it from Mill Street. There were even bits of toilet paper floating down the river.
“We’ve spent the best part of a year unable to access Seedhill Road while Scottish Water installed a ‘state of the art’ new sewer system.
“Then the first sign of rain, the river is turned into a toilet.”
The college IT expert said he heard visitors, either American or Canadian, remark that the river was “disgusting”.
Dave added: “I was so sorry to see the swans on the other side of the bridge.
“After they had put their heads and necks underwater, it came up brown.
“I just cannot understand why this practice is still deemed acceptable.”
The Scottish Water authority confirmed the sewer had become “overwhelmed” and the river was used as a release valve to prevent sewage backing up into bathrooms.
A spokeswoman said: “During heavy rainfall, the sewer network can become overwhelmed and we must protect our customers and their homes and businesses from sewer flooding.
“On Monday, a combined sewer overflow - a piece of infrastructure which acts as a controlled release system at times of heavy rainfall - operated as it should by releasing dilute waste water into this local watercourse.
“The waste water first passed through a screen to remove any debris.
“We have permission for sewers to overflow during heavy rainfall via environmental licences from our environmental regulators, Scottish Environment Protection Agency.
“Without this system in place, the sewer network could back up, flooding homes, businesses, roads and open spaces with diluted sewage and rainwater, from manholes, drains and toilets.”
And she claimed: “The level of untreated sewage in storm water that is discharged is very dilute, so is unlikely to cause harm to the environment.”
