Barratt has been heavily fined after polluting a tributary of the River Tamar in Cornwall with raw sewage.
The house builder also paid a vet bill after a dog fell ill at the time of the incident, between 31 August and 11 September 2009.
Barratt admitted to the charge, brought by the Environment Agency, at Bodmin Magistrates' Court this week.
It was fined £10,000 with £3,448.93 costs and a £15 surcharge
The court heard that Barratt had entered into a service contract in July 2009 to maintain the pumping station, and sewage monitoring equipment, on the 84-home Calcos Place estate at Kelly Bray, near Callington.
But on 2 September, the Environment Agency received a phone call from a resident, complaining of sewage fungus in their garden stream. On 11 September, when officers from the agency arrived, they found that samples of the water showed high levels of pollution.
The resident's dog fell seriously ill, and vets said this could have been down to the sewage leak.
In defence, Barratt said that the pumps in the station had become clogged, and subsequently failed, causing the sewage leak.
The house builder cleaned up the spill by lunchtime on the day after it was reported, with the vet bill also paid.
The company, which accepted full responsibility for the accident, said the experience had been “a harsh lesson”.