KMS not sure exactly what you are looking for and with the sad new coming out of Scotland at the moment this is clearly a topic which should be taken seriously. Have you looked at the acop? http://books.hse.gov.uk/...alogueCode=9780717617722 If you are talking about hot and cold water systems rather than cooling tower which I suspect is the case in most small retail units then control will be most likely by temperature manipulation and page 49 may contain the information you are looking for. But remember to read this in conjunction with the other appropriate sections of the acop/guidance. The HSE also do a very good DVD on this subject http://books.hse.gov.uk/...alogueCode=9780717662616 Pub you do have to pay for this.