Plumbing Africa April 2020 | Page 34

34 DESIGN: DEAR MR PLUMBER 34 DESIGN: DEAR MR PLUMBER Notes on a drawing: Part 2 By Vollie Brink This is Part 2 of an article in which I explore flaws in the drawings of other designers, where I have been asked to comment on the design. Design consists of the calculation of: Volumes, Flowrates, Velocities, Gradients, Minimum and Maximum Pressures, Temperatures, and more. All of these require engineering calculations based on assumptions and knowledge, and competence based on engineering education and experience of the practical installation of drainage and water systems. Design comes before construction and if there is a problem with the design then obviously there will be a problem with the construction. If, for instance, the wrong fixtures and wrong hot water generation plant and wrong pump system is designed, then the installation will also be wrong and a failure, and if the system was described or specified by a ‘note’ on a drawing then you can expect disaster. A complete design of a ‘system’ must include all the elements of the total system. You cannot design a water system or a drainage system without specifying the fixtures that go with it to make it complete. In terms of the NBR, the total complete system from fixture to end is the responsibility of the designer as signed for on the application form for approval of the drawings and also why it is required that the designer must have PI insurance. The designer is the person who must sign off the work and issue a Form 4, Certificate of Compliance, which is all in the case of a rational design. A rational design may only be evaluated in terms of the performance ‘regulations’ as you will find in the relevant NBR Part, Addendum. However, there is no such Addendum for the design of a potable water system. If you find such a vague note on a drawing, where do you begin? Are you going to do the design? If so, do you have PI insurance for design? and are you competent as per the NBR to do design beyond the ‘deem-to-satisfy-rules’? If your answer is positive, are you going to start with the drawings, and do it for free? You are supposed to be issued with a set of drawings which were approved by the office of the BCO. The drawings issued to you must also have all the necessary documentation with all the specifications and detailed information for you to carry out the construction without www.plumbingafrica.co.za @plumbingonline @plumbingonline @PlumbingAfricaOnline April 2020 Volume 26 I Number 02