22
FEATURE
Urban stormwater management manual – line drawings
Fig . 1 Fig . 2 Fig . 3 Fig . 4
• Fig 1 is commonly known as a French Drain . SANS 10400 : P provides in depth drawings and measurements , a copy of which every plumber must have . Bear in mind there may also be construction aspects to be considered e . g ., SANS 1200 DB , 1200 LB and 1200 LD .
• Fig 2 shows the addition of a geotextile lining as a filtration layer to prevent external fine soil particles being washed into the filter material and clogging it .
• Fig 3 shows the addition of a pipe to promote more rapid drainage . This is the most common type of sub soil drain . The pipe is perforated to allow easy entry of water and can be rigid or flexible videoed adequate compressive strength is achieved to prevent collapse .
• Fig 4 shows two further variations – an impervious cap for situations where the drain is intended to collect only subsurface flows , and bedding material for cases where the base of the excavation is unsuitable as a pipe support .
More recent developments of subsoil drainage systems have included a range preassembled geocomposites comprising polymer-based drainage cores bonded with filtration geotextiles . These are available
The selection of material must suit the application .
www . plumbingafrica . co . za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline August 2022 Volume 28 I Number 6