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on-grade inlet, on a sloping gutter, from which any flows bypassing the inlet can run away, with
bypasses or overflows being directed to downstream pits or out of the system.
At one stage there was also an ILLUDAS pit type that no longer appears in DRAINS. It is described in
the Help System.
Initially, DRAINS followed ILSAX (O’Loughlin, 1993) by using equations employing various curve-fitting
factors, but this approach was superseded by inlet capacity relationships defined as a series of points, as
shown in Section 2.4.6, rather than by equations. Further information is given in the DRAINS Help
system. Sets of inlet capacity relationships are available to users of DRAINS in the new format. These
were obtained from published sources, mostly smoothed graphs fitted to experimental data from the
testing rigs operated by the University of South Australia (www.unisa.edu.au/uwrc/rig.htm) and the New
South Wales Government Manly Hydraulics Laboratory (http://mhl.nsw.gov.au/www/welcome.html).
The new relationships have been extrapolated well beyond the ranges of the published relationships
using hydraulic principles, allowing for approach flows up to 2.5 m3/s for on-grade pits and depths of
ponding of up to 0.6 m for sag pits. None of these relationships have been approved by the originating
authorities. It is up to each user of DRAINS to determine whether they are suitable for their purposes.
Users can readily modify the relationships.
The available relationships for New South Wales apply to the pits described in Table 5.13.
Table 5.13 New South Wales Pits
Pit Type
Size
Kerb Inlet
Dimensions
Grate Size
Comments
NSW Roads
and Maritime
Services,
(formerly called
the RTA and
DMR) pits
(DMR, 1979;
O'Loughlin,
Darlington and
House, 1992)
and tests
carried out for
the RTA in the
1990s
SA1
1.0 m wide x 0.15
m high
1 m x 0.45 m
A kerb inlet-grate combination
depressed by 25 mm below
normal gutter levels
SA2
1.83 m wide x
0.15 m high
0.915 m x 0.45
m
As above
SA5
2.745 m wide x
0.15 m high
0.915 m x 0.45
m
As above
SF1
Median pit with
cover
none
As above
SO V-Channel
None
0.7 x 0.7 m or
0.7 x 1.4 m
V shaped pits located in VChannels
SK V-Channel
None
0.825 x 0.7 m or
0.825 x 1.4 m
V shaped pits located in VChannels
Hornsby
Council Pits
0.9, 1.2, 1.8,
2.4, 3.0, 3.6
and 4.2 m
wide lintel
0.9, 1.2, 1.8, 2.4,
3.0, 3.6 or 4.2 m
wide x 0.15 m
high
0.915 m x 0.45
m
Essentially the same type as
the RTA Pits
NSW Dept. of
Housing (1987)
RM10 Pit
1.68, 1.8, 2.4
or 3.0 m lintel
1.68, 1.8, 2.4 or
3.0 m wide by
0.15 m high
0.9 m x 0.5 m
A similar type of pit to the RTA
pits
none
0.9 m x 0.5 m
A grated pit used on
accessways
0.85, 1.2, 1.8, 2.4
and 3.0 m wide by
0.15 m high
0.9 m x 0.5 m
No grate or Durham Cast iron
grate
NSW Dept. of
Housing (1987)
RM7 Pit
Sutherland
Shire Council
(1992)
0.85, 1.2, 1.8,
2.4 and 3.0 m
lintel
The set of pits shown in Figure 5.21 was the basis of both the RMS (RTA) and Hornsby Council
relationships, which have different forms. The former allows for longitudinal slopes while the latter
provides a single relationship for all slopes.
Relationships developed for Australian Capital Territory are detailed in Table 5.14
DRAINS User Manual
5.24
November 2014