Bradham Lane is closed in both directions due to burst water main between St John's Road and the B3178 (Salterton Road).
The road is likely to remain closed for some time, and traffic is being diverted via Marpool Hill, Hulham Road and Pound Lane.
The Stagecoach 57 bus service is affected.
A burst water main is affecting water services in parts of Cornwall, leading to some cases of water discolouration.
Posting on their website, South West Water said they are carrying urgent repair work and apologised for any inconvenience caused.
Residents on the Isles of Scilly have been told they face a 45 million pound bill to upgrade their water and sewerage system - to bring them in line with European standards.
Leading councillors on the islands warned today about the impact on tourism - and said water bills could soar - unless alternative funding can be found.
The local council has written to every household on the islands about the proposals.
The Environment Agency has admitted it made a mistake in water tests in Lyme Regis which led to one beach in the town being recorded as failing basic water quality standards.
The town council is angry at the results and is worried they could put tourists off booking for next season. Richard Lawrence reports.
Cornwall's largest natural freshwater lake is being surveyed by divers for the first time. Scientists hope the study of Loe Pool near Helston will help them find out more about what goes on under the water. Kathy Wardle reports.
Tests of water quality on beaches at Exmouth and Budleigh show that they continue to meet EC standards for bathing, according to East Devon District Council. While heavy rains have led to some overflow from storm drains, this has not affected weekly tests.
The council says both beaches are now included in the South West Water Beach Live scheme. This provides the latest information on water quality.