HEALTH AND SANITATION
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iii. overland flow to a sewer grate; or
iv. using an air gap in the case of above-ground tanks.
6. Discharging overflows to a soakaway pit
a) Consult applicable provincial/district and local guidelines regarding the design and installation
of soakaway pits.
b) If there is limited space for a soakaway pit or if the soil has low permeability, it is
recommended that the soakaway pit has its own overflow, discharging overflows to grade or
into a storm sewer.
7. Incorporating a RWH system as part of a stormwater management system
a. Consult relevant authorities regarding how to incorporate an RWH system into other
stormwater management systems.
Maintenance of overflow
1. If the overflow drainage piping discharges above grade, it should be inspected annually.
a) The point at which the overflow discharges should be examined for signs of erosion. A splash
pad or several small rocks can be placed at the discharge point to protect the area from
future damage.
b) The coarse screen at the end of the overflow drainage pipe should be inspected for dirt and
debris and, if necessary, cleaned and/or replaced.
c) If removing the coarse screen for cleaning or replacement, the inside of the overflow drainage
pipe should be inspected for objects or debris that may cause clogging.
2. If the overflow drainage piping discharges below grade, inspection and/or repair is necessary only
when signs of a blocked or poorly performing overflow-handling system are observed, such as:
a) water damage to the rainwater tank, tank lid or access hatch, or components located inside
the tank above the maximum water level;
b) water leaking from the tank lid or access hatch;
c) water backing up rainwater inlet lines and top-up drainage piping; or
d) water leaking from downspout-to-conveyance drainage pipe transitions, or from top-up
system air gap.
3. If any of the above signs are observed, the components of the overflow system should be inspected
and repaired.
a) Inspect coarse screens located on the overflow drainage pipe for debris that would impede
water flow, and clean, repair or replace the coarse screen as necessary.
b) Inspect all overflow drainage pipes using a pipe scope for signs of blockages or pipe damage.
All debris/blockages must be removed from the overflow drainage piping, and all damaged
sections of pipe must be replaced.
c) If the overflow drainage piping discharges into a soakaway pit, the pit may be clogged with
dirt and debris and may not be providing sufficient infiltration capacity. It may be necessary to
repair and/or expand the pit to accommodate overflow volumes.
d) If there are no obvious problems with the overflow system, it may be necessary to simulate an
overflow event (or observe one during a rainfall event). Monitor the system visually or by pipe
scope to determine what is causing the problem.
4. While inspecting, cleaning or repairing components of the overflow system, follow all necessary
safety precautions as per the South African Safety, Health, Environment and Quality, if entry into the
rainwater storage tank is required. PA
In the final article of this series we look at the Financial Assessment
of a RWH system.
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August 2019 Volume 25 I Number 6
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