21
HEALTH AND SANITATION
21
HEALTH AND SANITATION
The design of the RWH system includes the planned route of overflow drainage piping
from the tank to the overflow discharge location.
lines (gas, electricity, water, stormwater, wastewater, phone or cable lines) in the area where
digging will take place to accommodate buried overflow drainage piping.
3. Overflow pipes
a) Overflow drainage pipes
a. Pipe material
i. Pipe selected must be approved by applicable national/provincial/ local codes and industry
standards.
b. Pipe size and slope
i. Overflow drainage piping shall be sized to ensure that the capacity of overflow drainage
pipes is no less than the capacity of the rainwater conveyance drainage pipes.
ii. Ensure a minimum slope of 0.5-2% (the greater the slope the better) is maintained
throughout the pipe length.
c. Tank connection
i. Overflow drainage piping shall exit the tank at a height no lower than the rainwater
conveyance drainage piping, or, ideally, at a height 50mm below the bottom of the
conveyance drainage pipes entering the tank.
d. Consult applicable provincial/local codes and regulations pertaining to the installation of
drainage piping.
4. Discharging overflow to grade
a) Overflow must be discharged at a location where rainwater will not pond or collect around
building foundations.
b) Erosion prevention measures should be taken.
c) A screen should be installed where the pipe terminates to prevent the entry of birds, rodents
and insects.
5. Discharging overflow to storm sewer
a) Overflow drainage piping cannot be directly connected to a storm sewer, unless approved by
local authorities.
b) A direct connection may be permitted if a backwater valve is installed on the overflow
drainage pipe. Consult local authorities for approval.
c) An indirect connection can be made by:
i. overflowing to an interceptor tank, which then overflows into the storm sewer;
ii. overflowing to a soakaway pit, which then overflows into the storm sewer;
August 2019 Volume 25 I Number 6
www.plumbingafrica.co.za