Authorities and local governments have many views on the subject. Depending on where you are and who you are dealing with, you could encounter anything ranging from the simple 1950's solution of "put in the largest pipe you can buy and just get rid of the water," to get the most intricate systems incorporating stormwater detention and pollutant traps.

Minicipal councils which have responsibility for run-off into waterways, especially high visibility waterways, are going to get lengths to show they are doing the right thing. They expect the same from everyone else.

Dual occupancy and medium density developments are becoming very popular and authorities are formulating new regulations to provide better storm drainage in these circumstances. At the same time authorities are becoming increasingly strict and expect all stormwater work to be done according to their standards. In many multi-dwelling situations, local authorities enforce a discharge rate in litres per minute. On-site detention of the right capacity with an orifice sized to meet the predetermined rate has become the norm rather than the exception.

While on-site stormwater detention (OSD) and the use of pollutant traps is becoming relatively commonplace, stormwater regulations are still not uniform. Authorities together with key players in industry are gradually developing guidelines, but there are no uniform standards yet.

Some Sydney councils have adopted a common OSD policy and do not allow any development to increase the peak discharge at any point downstream for any storm event up to a 100-year storm. These councils want to stop urban flooding problems caused by a combination of new development and old drainage systems.

OSD policies have already been adopted by various Sydney councils, but some of these are based on a site by site analysis rather than a regional overview. The effectiveness of a site based policy generally does not carry very far downstream if the outlet is relatively large and the storage small. Inadequate capacity OSD systems may allow water to discharge without significant retention or will simply overflow in a storm of long duration.

A significant contributor to the problem is the fact that local government does not have the money to fund drainage infrastructure programs to keep up with developments. The authorities' view is that they must develop a catchment wide OSD policy.
Some older stormwater systems are undersized and councils will serverely limit discharges in an attempt to avoid a major rebuild. This means in some circumstances, if you are designing a system just for a house extension, you could be confronted with a reduction in the allowable site discharge. In some areas the cost of a system to meet the requirements of the allowable discharge rate could add as much as $20,000 to the total cost of your extension.

Another important thing to remember is that, in many areas, different rules may apply to for dual occupancy and medium density developments compared to a residential extension. There are many hidden costs, for example if you choose above ground detention ponds that are more than 300m deep you may need to install an isolation fence.