Plumbing Africa May 2022 | Page 19

FEATURE 17
Nonetheless , standards are living documents and are subject to review at regular intervals . It is worthwhile registering to receive the SABS newsletter which keeps one up to date with such reviews and more importantly when such standards are out for public comment . The newsletter is free on www . sabs . co . za .
The issue of WATER being brought into the National Building Regulations is currently under discussion so hopefully this matter can be resolved sooner than later .
Pipe sizing Sizing a water distribution system for plumbing , residential and commercial , requires consideration of factors , from pressure and fixture count to pipe material .
Calculating all contributing factors is essential to meeting standards requirements , as well as ensuring proper operation of the system . the inner diameter of the pipe . Because of this relationship , the size of the pipe can be adjusted to achieve the necessary flow rate that is required to service the desired number of fixture units . However , the maximum number of fixture units capable of being serviced is dependent on the available pressure in the system .
Either manually or using a sizing calculator , input the incoming pressure and then list known pressure losses . Every element in the water system , from the meter to a bend , results in pressure losses . Typical friction losses / gains include :
• Water meters
• Pressure reducing valves
• Submeters
• Elevation loss / gain .
Once you have tabulated the friction losses , you can determine the total pressure drop , which is reported on the building plans .
Tabulating losses The first step in pipe sizing is determining the water pressure coming into the building from the city ; for both residential and commercial structures , there is pressure regulation at the water meter , which is where engineers and designers would start tabulating friction losses .
Understanding the friction losses contributing to a system enables the designer to translate those losses into an average pressure drop per 100 feet for the system . The pressure drop of a system is a fundamental parameter required for the calculation of the system velocity and , ultimately , the flow rate ( aka , ‘ demands ’).
Plumbing standards have established guidance for the number of fixture units that can be serviced by a given flow rate . In addition to its dependence on pressure drop , flow rate is also dependent on
Typical pipework configuration
May 2022 Volume 28 I Number 3 www . plumbingafrica . co . za