Regional pit types

Regional pit types

The examples and pit data base files supplied with DRAINS contains pit inlet capacity relationships for a number of types of pits used in various regions of Australia. More pit types can be added as reliable information on pit inlet is obtained. Please contact Watercom if you have information that you would like to have included in DRAINS.

All the on-grade pit relationships supplied have been extrapolated up to an approach flowrate of at least 1.0 m3/s, and all sag pit relationships to a ponding depth of 0.6 m. Considerable judgment has been used in these extrapolations, and their accuracy cannot be guaranteed. If, after reviewing the relationships you wish to use, you wish to change the flowrates, you alter the relationships in the pit data base, or enter new relationships. Because of these uncertainties, the pit capacity information provided with DRAINS is only indicative. It is the responsibility of users to check the relationships that they use and satisfy themselves that these are suitable for the design or analysis task being undertaken.

The following table gives general information on the pits for which New South Wales relationships are supplied.


References for the above are:
  1. New South Wales, Department of Housing (1987) Road Manual, Sydney New South Wales, Department of Main Roads (1979) 
  2. Model Analysis to Determine Hydraulic Capacities of Kerb Inlets and Gully Pit Gratings, Sydney, 1979
  3. O'Loughlin, G.G., Darlington, D. and House, D. (1992) Mathematical Description of Pit Entry Capacities, I.E.Aust. International Symposium on Urban Stormwater Management, Sydney Sutherland Shire Council (1992) Urban Drainage Design Manual, Sutherland
The following table provides information on the Queensland pits.  


This replaces the 2003 set that included the following pit types:

The only Victorian data available is the VicRoads pits, which have the following characteristics:

These relationships have been obtained by extrapolating the curves given in the VicRoads Road Design Guidelines Part 7, Drainage, 1995.

South Australian Pit information obtained from hydraulic testing at the University of South Australia covers the pit types listed below:

Data for the Australian Capital Territory, taken from  ACT Government  Urban Stormwater, Standard Engineering Practices, Edition 1, is available for the pit types shown below:


There is no published test data on pit types used in Western Australia, but a data base has been developed for Department of Main Roads pit types using the Generic Spreadsheet that implements methods from the US Federal Highway Administration HEC-22 manual. The pit types covered are: