In its draft report on secondary water use in the ACT, the commission says making good decisions in the face of evolving uncertainty and the wide range of potential supply and demand options required an adaptive and integrated analytical framework, supported by clear lines of accountability and responsibility.

''The commission found no such framework in the ACT,'' the report says. ''But rather an unclear, disjointed and unresponsive approach to decision-making.''

In the interests of ensuring a more effective approach to maintaining the ACT's urban water supply and demand balance at least cost, the commission recommends an adaptive, integrated single analytical framework for consideration by the ACT government.

Senior commissioner Malcolm Gray said the three key elements of water planning: the Environment Directorate and its minister, Actew and the regulator were not working closely together.

The 140-page report recommends capturing stormwater go no further than the trial of the inner north pilot project under construction.

The report says given the current level of water security, the commission found no solid basis for government subsidising private secondary water options, including the subsidy of up to $1000 for water tanks at private residences.

Similarly, in relation to mandatory water efficiency requirements placed on estate developers, it was not evident the costs of government intervention were outweighed by the benefits. The commission recommends the ACT government review the requirements in the context of an adaptive and integrated planning framework.

Reticulated water in the ACT is among the most expensive in Australia. In a foreword to the report, Mr Gray says that when primary water is plentiful, no secondary source delivers water as cheaply.

''Following the rains of the last two years, the very substantial investment in improving the primary water system and the sizeable reduction in per capita consumption, primary water is plentiful at the moment and is likely to remain so for some time.''

However, he warned Canberra would again face water shortage and said planning for this was necessary.

The commission recommends the government develop a clear approval pathway for private sector multi-dwelling secondary water schemes, such as third pipe, stormwater harvesting and grey-water schemes. Mr Gray said that without a third pipe, all secondary water use options were not practical.

Environment Minister Simon Corbell said the government welcomed the commission's finding that the ACT would be water secure for at least the next 20 years, with only the possibility of rare water restrictions. He said the government had always believed there should be a trial of the inner north stormwater project, which it would undertake.

He said the report had focused on the economics of water reticulation. Urban stormwater projects had other values such as improving water quality and biodiversity. The government would still need to have regard to those when making decisions about other wetland projects.

An Actew spokesman said the report made an excellent contribution to ensuring the ACT continued to strike the right balance between traditional supply, alternative supply and demand measures to achieve water security. Submissions on the commission's draft report are due by June 12. The commission is required to present its final report to ACT Treasurer Andrew Barr by June 30.

The draft report is on the commission's website, icrc.act.gov.au.