Sludge 04 : A general term for soft mud-like deposits found on heat transfer surfaces or other important sections of a cooling system. Also found at the base of calorifiers and cold water storage tanks
Health and Safety Executive (HSE), Legionnaires' disease: The control of legionella bacteria in water systems (Approved Code of Practice and general guidance), Merseyside, England, UK 2013. ISBN 978 0 7176 1772 2, http://www.hse.gov.uk/aboutus/meetings/hseboard/20 13/220513/pmayb1352a.pdf, (Hlth and Sfty - Brit) {722}