# The Water Supply (Water Fittings) Regulations 1999, Paragraph 24


No supply pipe or secondary circuit shall be permanently connected to a closed circuit for filling a heating system unless it incorporates a backflow prevention device in accordance with a specification approved by the regulator for the purposes of this schedule.

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Source: https://www.legislation.gov.uk/uksi/1999/1148/schedule/2/paragraph/24 (the official version)
Page: https://openlegislation.uk/water-supply-water-fittings-regulations-1999/schedule-2/paragraph-24
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.