54 HEALTH AND SANITATION
RAINFALL REGION
Gutters and downspouts a. Gutter and downspout materials For gutter and downspout materials, aluminium or galvanised steel are recommended. Copper, wood, vinyl, and plastic gutter and downspout materials are not recommended. b. Gutter slope
• Slope gutters in the direction of the location of the rainwater storage tank.
• Ensure a minimum slope of 0.5 – 2 %( the greater the slope, the better) is maintained throughout the gutter length. c. Gutter size( SANS 10400-R)
• Any valley or gutter shall have a cross-sectional area of not less than that given in Table 4.2, for the rainfall region in question. Such requirements in respect of any downpipe shall be deemed
Table 4.2: Roof valley and gutter sizes
Summer 140mm 2 Year round 115mm 2 Winter 80mm 2
INTERNAL CROSS-SECTIONAL AREA OF VALLEY OR GUTTER PER M 2 OF ROOF PLAN AREA SERVED to be satisfied where the internal cross-sectional area of such downpipe is not less than 100mm 2 per 1m 2 of roof plan area served by such downpipe, provided that such internal crosssectional area is not less than 4 400mm 2.
• Areas experiencing intense storm events need wider gutters than areas with less intense rain events. The gutters should be sized so that they adequately move rainwater run-off from a 100-year storm event. A 100-year storm event has a 1 % chance of occurring every year and produces rainfall with great intensities. d. Location and spacing of downspouts
• Ultimately, the locations of downspouts depend on the configuration, architectural features, and appearance of the building. Whenever applicable, locate them near the storage tank.
• Each downspout should drain a maximum of 15m of gutter. However, the very design of the building might prevent the installation of more gutters.
• Avoid locations where water must flow around a corner to reach a downspout. e. Downspout size
• In general, downspouts come in standard profiles and sizes. These should be suitable for most typical residential roof drainage areas and gutter lengths.
• The gutter and downspout size required is highly dependent on the amount of gutter and the spacing of the downspouts.
October 2018 Volume 24 I Number 8 www. plumbingafrica. co. za