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Jult 27th, 2012

The DRAINS procedure for generating storms with ARR87 rainfall patterns has been improved.  You can now quickly generate multiple storms using tabular data obtained from the BOM (Bureau of Meteorology) web site.  The BOM web site lets you generate a table of coefficients or a table of intensity values (IFD table).  The table of coefficients is recommended if you wish to use the BOM IFD data.  If you wish to use Council IFD data then you can generate a BOM IFD table and replace the BOM intensity values with Council values. You can add extra lines to the table to provide any missing data (e.g. 25 minute storms are missing from the BOM IFD table).

June 12th, 2012

The DRAINS installation procedure has been amended to allow silent installation.  This should be of interest to IT administrators who need to install to many computers.  Click here  for more details.

February 9th, 2012

The pit data bases in DRAINS for Victoria, WA and Tasmania have been updated.

July 7th, 2011

There is a new User Manual for DRAINS available from the Download page.

January 7th, 2011

The Help System in DRAINS has been updated.  The full unsteady flow hydraulic model has been renamed the Premium Hydraulic Model to better distinguish it from the Standard Hydraulic Model. 

December 11th, 2010

A new hydraulic model is now available.  The new Standard Flow Model will replace the Basic Flow Model that has been in service since 1998.  It offers improved stability and takes advantage of multi core processors to improve run times.  The Basic Flow Model will continue to be available for existing jobs.

The Standard Flow Model solves the full St Venant Equations for flow in pipes and channels.  The St Venant equations account for storage in pipes and channels, and this may have implications for how you formulate models.  For example, if you are using large diameter pipes to provide storage you may have been modelling these as detention basins in the Basic Flow Model.  This is no longer necessary with the Standard Flow Model.  In fact you should remove such detention basins from the model when it includes these large pipes.

The Standard Flow Model treats overflow routes in the same manner as the Basic Flow Model.  It ignores storage effects in overflow routes.  The Full Unsteady Flow model solves the St Venant equations in overflow routes (as well as in pipes and channels).  This storage can significantly reduce peak flows in overflow routes leading to a more realistic assessment of surface flooding with the Full Unsteady Flow Model.

The Basic Flow Model has struggled with some complex components.  For example, a car park with a pit/sump outlet needed to be modelled as an "off-line" detention basin.  With the Standard Flow Model it can be modelled as a simple sag pit where you specify depths vs storage for the volume ponded in the car park.

The Standard Flow Model will allow us to further develop DRAINS to better cope with complex arrangements such as multiple drowned outlets from a detention basin etc.

September 15th, 2010

The unsteady flow module in DRAINS has been updated.  It can now take advantage of multi core processors to greatly improve run times.  This feature is disabled by default.  It can be enabled in the Project / Options menu item.

March 25th, 2010

The unsteady flow module in DRAINS has been updated.  It can now check for signs of instability in pipe flows when a run is completed.  If instabilities are found, it can apply numerical damping to the affected pipes (at your discretion) to reduce or eliminate them.

November 9th, 2009 

DRAINS has been updated.  It can now check for updates (newer versions) since you last installated it - see under the Help menu item.

There is a new user manual and on-line help system within DRAINS.

October 13th, 2009 

DRAINS pipe design procedure has been improved.  This can result in a more economical design in some situations.

August 24th, 2009 

PIPES and PIPES++ have been updated.  They now

  • import the latest DXF files.
  • have a new on-line Help system compatible with all versions of Windows including Windows 7.
  • include Property Balloons which are useful to quickly review basic pipe and node data in networks that are unfamiliar to you.  They can be turned on or off from the View menu.  They are off by default.
  • can import polylines, and arcs on the background layer.  Arcs are sometimes used for drawing cul-de-sacs in a dxf file.
  • include support for panning and zooming using the mouse wheel.

July 2nd, 2009 

The latest version of DRAINS has improved DXF input capability.  It now supports the latest versions of DXF files and also supports polylines, arcs and circles on the background layer.

June 4th, 2008 

The latest version of DRAINS has pop-up balloons that show a summary of data for pits, pipes etc as you move the mouse cursor over the pit, pipe etc.  If you find these balloons distracting, you can turn them on/off from the View menu.

June 4th, 2008 

The Extended Rational Method (ERM) in DRAINS has been improved.  It now provides the option of automatic calibration against the standard rational method for peak flows from sub-catchments.  Such calibration is required by some Councils in Queensland.  It was found that the procedure used in the old ERM could produce higher peak flows than the standard rational method if partial area effects dominated in the latter.  You can still use the old procedure, but you now have the option of better calibration against the standard rational method if you are required to do so.  The procedure is discussed in detail in the on-line help system - look up ERM in the index, read the topic and then follow the link at the end for more technical details.


June 4th, 2008 

There have been some minor changes to the folder structure of DRAINS to suit Vista.  When you install Drains to the default folder, a new folder C:\ProgramData\Drains will now be created.  The default data base file DRAINS.DB1 will be stored in this folder.  This was necessary because Vista does not allow Drains to change DRAINS.DB1 when it is located under C:\Program Files.  It appeared to allow such changes, but was in fact storing the file somewhere else, and the location was different for each user.  This was causing confusion with multiple copies of DRAINS.DB1 being stored.  The new arrangement should help reduce this confusion.  Please note that, under Vista only, you will not be able to see the folder C:\ProgramData unless you are logged on as administrator.

May 13th, 2008 

The unsteady hydraulic model in DRAINS has been improved.  Sloshing of water (surging back and forth) in open channels and overflow routes was sometimes observed in DRAINS results.  This has been reduced with additional numerical damping applied to inertia terms in the unsteady flow equations.  Also shock losses at pits with very small loss coefficients were slightly overestimated in the past.  These have been corrected.  There may now be slightly greater capacity through pipes, but any changes are expected to be small.

May 5th, 2008 

The Queensland Urban Drainage Manual (QUDM) provides a method for setting out hand calculations for the design of drainage systems using the rational method.  QUDM provides several charts (based on Missouri charts and Hare charts) for the estimation of pit shock loss coefficents to be used during this process.  Various Councils in Queensland have adapted this method and require calculations submitted for DAs to be in their individual amended formats.

DRAINS has been improved to provide output from rational method calculations in the format required by various Councils in Queensland.  This should be very useful if you need to submit design calcuations to a Council in Queensland.  More details are available in the latest version on-line help system (see QUDM pipe design procedures and QUDM design outputs in the index).

The QUDM charts are now emulated in DRAINS.  These are useful for estimating shock losses in any system (not just in the rational method design procedures required by Queensland Councils).  More details are available in the latest version on-line help system (see Pit Ku coefficients in the index).

February 14th, 2008

In DRAINS, the treatment of outflow from a detention basin into a pressurised pipe has been amended to allow for an extra loss of V2/2g to allow for conversion of potential energy to kinetic energy (ie Energy Line in the basin to HGL in the pipe).

December 13th, 2007

The unsteady flow module in DRAINS has been updated to provide better stability in the behaviour of culverts, headwalls and detention basin outlets.

November 13th, 2007

A Synthetic storm generator has been added to DRAINS (as a button in the rainfall dialog box).  Synthetic storms are intended for use with the Extended Rational Method.  Storms patterns from ARR87 can still be used with with the ERM, but use of a synthetic storm will generally give a better match to simple rational method estimates of peak flow because the synthetic storms are based on the same IFD data used in simple rational method calcs.  You can find more information under "Synthetic storms" in the on-line help system.

October 24th, 2007

The Extended Rational Method has been modified.  It is now identical to the Modified Rational Method as used in the US.  This is a time-area type model with infiltration loss proportional to rainfall intensity.  The loss at any instant is calculated using the rational method coefficient.  Loss = (1-C) x Rainfall Intensity. This should typically produce slightly less runoff than the previous version of the ERM.

October 22nd, 2007

Pumps have been added to DRAINS.  It can now model pumps in both the basic model and the unsteady model.  There is a new button on the toolbar to draw a pump.

May 25th, 2007

At the request of users we have provided the option of specifying either volume or surface area vs elevation for detention basins.  In general we would recommend the use of surface area vs elevation.  DRAINS uses the prismoidal formula to calculate volume from surface area.  In some cases this formula may not be ideal (eg a horizontal pipe used as a detention basin).  In such cases you can choose to specify volume vs elevation.  You can choose which option you wish to use under the Project / Options menu item.  Once you have specified data for one basin you no longer have the option to change between surface area or volume.

January 31st, 2007

The capabilities of detention basins in DRAINS have been extended.  They can now model infiltration losses to the surrounding soil if you specify permeable floor/walls.  To accomodate this the table of Elevation vs Storage Volume has been replaced by a table of Elevation vs Surface Area and a new table of Elevation vs Perimeter has been added (only needed if you have permeable floor/walls).  Old files will continue to use the table of Elevation vs Storage Volume and infiltration calculations will not be available on these files.   If you need to convert an old file to permit infiltration calcs refer to the on-line help system or contact Bob Stack on 02 6649 8005..

October 27th, 2006

The unsteady flow engine in DRAINS has been modified in Version 2006.18.  The basic flow engine is unchanged.  The rest of this section applies to the unsteady flow engine only.   Prior to  Version 2006.18 flows coming off catchments entered the system at a pit or node even if the user specified some or all of this flow was carried by an incoming overflow route.  Starting with Version 2006.18 if the user specifies some or all of this flow is carried by an incoming overflow route the flow is introduced as a lateral inflow along the overflow route instead of at the pit or node. 

After an unsteady run finishes the peak flow at the mid point of overflow routes is commonly shown on screen.   At the mid point of an overflow route half of the lateral inflow has entered the overflow route and the flow shown on screen now includes this flow.  Therefore the number may appear greater than earlier versions which did not include any lateral inflow at this location.

If you edit the data for an overflow route the maximum flow shown on the Cross Section Data page may be greater than the value described above.  This is because it is an estimate of flow at the downstream end of the overflow route and includes the full lateral inflow (as opposed to half the lateral inflow reported at the mid point).

If you customise the text to show maximum flow width for an overflow route (instead of maximum flow at the mid point) the width most commonly shown will be at the downstream end of the overflow route.  This is because DRAINS unsteady flow engine uses a staggered Depth/Flow grid where Depths are calculated at each end of a reach, and Flows are calculated at the mid point of a reach.

October 23rd, 2006

Watercom has moved office.  Our new phone number is 02 6649 8005 and our new address is:

15 Little River Close,    Wooli NSW 2462

September 14th, 2006

The DRAINS unsteady flow model has been extended to allow users the option of specifying storage vs elevation for sag pits.  This will be useful where accurate modelling of storage at a sag pit is important.  It will largely supersede the use of detention basins with pit/sump outlets in the unsteady model.

September 6th, 2006

The "Check HGL" feature in DRAINS described below (under June 21st) has been changed to a bottom up analysis.  This is an improvement over the procedure used in Australian Rainfall and Runoff Table 14.14 which relies on unnecessary assumptions about freeboard at the top of the system, and results in an unrealistic HGL calculated at the system outlet.  The HGL at the system outlet is now correct and pit freeboards are now more realistic.

August 21st, 2006

DRAINS can now export ASCII hydrograph files suitable for importing into 2D models such as TUFLOW.    It will export 3 files per storm: one for pipes, one for overflow routes and channels, and one for sub-catchments (see File/Export/Tuflow TS1 file menu item).

July 13th, 2006

DRAINS now runs about 30% faster than previously.  This should be useful if you have long run times.  


June 21st, 2006

Some Councils require HGL calculations to be presented in a tabular form that can be checked manually.   While DRAINS can present maximum HGLs and flows in tabular form, manual checking of these HGLs can sometimes be impractical because:
if some pipes are flowing part full, the basic DRAINS engine does backwater calculations to determine the upstream HGL in a pipe.  Manual checking of backwater calculations in a circular pipe is too complex to be practical.  If the unsteady flow model is used, detailed manual checking of results is impossible.
with the ILSAX and extended rational method models, the maximum flows and HGLs at the top of a system can sometimes be caused by a different duration storm to those at the bottom of the system.   In this case the maximum HGLs and flows shown by DRAINS are the worst case from both storms.  A manual check would need to consider each storm separately, rather than just the maximum values presented by DRAINS.

To assist in meeting the Council requirement for presentation of results a new feature has been added to DRAINS (under the Edit / Copy Check HGL to Spreadsheet).  The simplified HGL analysis is a top to bottom analysis similar to Table 14.14 of Australian Rainfall and Runoff 1987, using the pipe flows determined in a DRAINS analysis.  It should be noted that any top to bottom analysis does not provide realistic HGLs.  Realistic HGLs can only be obtained by starting an analysis from the bottom using a realistc HGL there and proceeding upstream.  Nevertheless, a top to bottom analysis is useful because it can demonstrate that a pipe system is capable of carrying the required flows (if the calculated HGL at the outlet is higher than the real HGL) and the results are suitable for manual checking.

May 22nd, 2006

The design procedure in DRAINS has been improved to allow different minimum pipe slopes for different diameter pipes.  This is now set in the Pipe Data Base property sheet for each pipe size.  The user can also change the trench width if desired in the same property sheet.

April 28th, 2006

The recently released unsteady flow engine in DRAINS has been extended with additional capabilities that allow modelling of situations that cannot be modelled with the basic engine.  Some examples include:
A situation where there is a sag pit downstream of an on-grade pit or pits and ponding at the sag pit can extend to drown the on-grade pit(s) further upstream.  In this situation the on-grade pit(s) initially act as on-grade pits (where inlet capacity is a function of approach flow), and when they become drowned they act as sag pits (where inlet capacity is a function of depth).  As the storm passes the ponding recedes and the pits again act as on-grade pits.  DRAINS unsteady engine automatically switches between on-grade pit data and sag pit data as the storm progresses to calculate the correct inlet capacity at each time step of the simulation.   Click here for more details.
A situation where there are different depths in gutters on each side of a road with some flow over the road crest.   Click here for more details.  A variation on this is the situation where a footpath forms a local high point or ridge and water from the gutter spilling over the footpath can flow into properties on the low side of the street.  This can be modelled in the same way as flow over the road crown.


March 24th, 2006

A new DRAINS module is now available that performs a full unsteady flow hydraulic analysis.  This model includes storage and inertia effects in overflow routes, channels and pipes.  If these storage effects are significant in a system, the unsteady flow model can produces smaller peak flows and lower peak water levels than those obtained from the basic DRAINS model.  Modelling of surface flows is more accurate with the unsteady flow model and problems such as overflow routes carrying water uphill in the basic model are eliminated with the unsteady flow model.   The unsteady flow module has been designed to run existing DRAINS models.   However, some additional data is required before these models can be run with the unsteady model (eg additional levels are required at each end of overflow routes, additional data is required for sag pits, etc).  DRAINS will guide you through the additional data that is required.  The unsteady model also provides animations of water levels in pipes, channels and overflow routes.  Click here for more details on the unsteady flow model.

November 14th, 2005

In DRAINS version 2005.15 results of a run can be saved with the .DRN file.  This can save time on large jobs where previously it was necessary to re-run the job each time you opened a .DRN file to see the results.

October 17th, 2005

In DRAINS version 2005.14 there has been a change to the method of calculating pit shock losses that can, in steep pipes flowing part full, result in a lower shock loss than previously calculated.  There can be a problem with simply applying a shock loss factor K to the velocity head.  Click for more information.

August 25th, 2005

In version 2005.13 a pan capability has been added.   Also the treatment of blocking factors for on-grade pits has changed.  Click here for more information.  In general, we recommend that you not use pit blocking factors across the board.  This can cause misleading results.  For example, blocking factors applied to all pits may reduce the amount of water entering the underground system so that it appears to function satisfactorily.  Removal of the blocking factors may force more water underground and this can lead to reduced capacity in sections of the underground system and consequent localised flooding which was not apparent with the blocking factors in place.

Another way to look at this is to consider what happens if say 5% of pits are blocked.  If you model blockage at all pits your model will be wrong at 95% of all locations.  If you don't model blockages your model will be correct at 95% of all locations.  You can always apply a blocking factor at an individual pit to test "what if" scenarios.

Of course, if you don't model blockage factors the changes in the treatment of blocking factors within DRAINS will be irrelevant.

June 11th, 2005

DRAINS can now print diagrams to PDF files (if you have Adobe Acrobat installed).  This may be useful if you cannot find a suitable driver for your printer / plotter to prepare network diagrams from DRAINS.

February 5th, 2005

Execution time for DRAINS has been substantially reduced.  If you noticed a slowing down in speed towards the middle of a storm run (in the status bar at bottom of screen) you should notice a substantial increase in speed.  This slow down occurred when the pipe system was pressurised and this part of the analysis is now much faster.

October 15th, 2004

Headwalls in DRAINS models have been modified to allow for a depth of water above the overflow level (previously considered negligible).

July 27, 2004

Some Queensland Authorities require that the ILSAX Model in DRAINS be calibrated to produce the same answers as the Rational Method Model.  This can sometimes be difficult because the models are so basically different.  To overcome this difficulty we have introduced the Extended Rational Method model which uses the same type of runoff coefficients as the rational method, but produces runoff hydrographs from rainfall patterns and so can be used for detention basin design.  Click here for a technical description of this model.


June 1, 2004

The on-line help system for DRAINS has been updated.

December 24, 2003

PIPES++ has been extended to include a fire flow analysis capability.  When you run a fire flow analysis a fire demand is automatically applied to each node in turn and HGLs and pressures are calculated.  The fire demand can vary with the type of area (eg residential, industrial etc).  The minimum HGL and pressure at every node due to a fire anywhere in the network is determined.  More details are available in the User Manual and the on line help system.  Merry Christmas.

November 17, 2003

A job containing a shallow pit with a steeply sloping outlet pipe has shown a fault in DRAINS when using the QUDM method to calculate shock loss for free surface flow.  With a large flow arriving in the pit the outflow is limited by the head available to overcome the shock loss at the pit outlet.  This is somewhat similar to inlet control at a culvert.   DRAINS did not check for this condition and consequently overestimated the outflow from the pit.  It has now been modified to check for this condition.  This is likely to affect only shallow pits with steeply sloping outlet pipes flowing part full where the QUDM method was specified. 

The Queensland Urban Drainage Manual (QUDM) provides a method for calculating shock losses in pits under partially full flow conditions.  It provides Ku values (in the range 0.5 to 1.0) for various pipe configurations.  However, it does not provide a value for a pit with no incoming pipes.  Previously, DRAINS used a value of 0.5 for this configuration (if the QUDM method was selected).  This has now been changed to 2.0 to be more consistent with the other values provided by QUDM.

DRAINS has been extended to provide an alternative method for calculating free surface shock loss at pits.  You can now specify the pressure loss coefficient for part full flow to be the same as, or some fraction of, the full pipe loss coefficient.  Unfortunately there is little published information on pit loss coefficients for pipes flowing part full.  In a study of various pit configurations by Marsalek, most of the measured pit loss coefficients for part full flow were in the range of one third to two thirds of the full pipe pressure loss coefficient (ref:  Marsalek, J., "Head Losses at Selected Sewer Manholes" - Special Report no. 52, American Public Works Associations, Chicago IL, 1985).

An error in DRAINS for calculating the depth in steep rectangular pipes discharging freely to atmosphere has been rectified.


September 18, 2003

The design procedure used in DRAINS to size pipes has been improved.  Occasional problems with unwanted flooding from unsatisfactory designs have been overcome.

July 3, 2003

The non pressure pipe hydraulic analysis has been improved.  Previously, it was assumed that uniform flow occurred in pipes.  Starting with version 2003.23 there is a backwater analysis done for each pipe flowing part full instead of assuming uniform flow.  Generally this will result in only small differences in a few results.  However, if the uniform flow assumption was very inaccurate the differences may be larger.  It is likely that water levels will be lower and capacities higher in these cases (ie the old results would typically be more conservative).  Perhaps surprisingly, this more sophisticated analysis takes only slightly longer to run - in some cases it may even run faster.

June 3, 2003

GIS Interface Modules for DRAINS and PIPES++ are now available.  These modules are sold as an optional extra to the normal software.  They allow transfer of data to and from Mapinfo MIF/MID files and ESRI Shapefiles (as used by Arcview).  They also allow transfer of multiple sets of results to the GIS for presentation purposes and to allow ready reference by non technical staff.

The convergence algorithm used by DRAINS for pressure pipe analysis has been improved.  This should remove the spikes that occasionally occured in hydrographs and HGL graphs due to a failure to converge to an accurate solution after the maximum number of iterations.

DRAINS and PIPES++ can now import a background layer from a DXF file into an existing job.  If there is an existing background layer, the new background can replace it or be added to it.


Questions or problems regarding this web site should be directed to bobstack@watercom.com.au .
or Phone 612 6649 8005 (International), or (02) 6649 8005 (within Australia)
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