Raw sewage can discharge from the Combined Sewer Overflow (CSO) at Sennen. If you want to know when your surf spot is polluted in real time, sign up to SAS's Sewage Alert Service at www.sas.org.uk/sewage-alert-service/ and receive a free text when the CSO discharges raw sewage.
The Sewage Alert Service covers over 200 beaches around England and Wales. The CSO at Sennen is at Sennen Pumping Station. SAS are working with South West Water to ensure you know when there's a raw sewage spill at Sennen. Diffuse pollution can also impact the water quality at Sennen. For more information on Sennen you can also look at: http://www.environment-agency.gov.uk/static/documents/bwprofiles/BW_30700_Sennen.pdf