Most presently “single-residential” properties cannot be developed to multi-residential (depending on zoning) until connected to deep sewer.
The Western Australian State Government has undertaken an extensive sewer infill policy where all lots in the metropolitan area will be connected to sewer within the next few years – thus providing more development opportunities and softening the environmental impact on the ground-water from the previously used septic systems.
Once sewer is provided a property must be connected within 18 months – even if the property is not being developed. This will ensure that all present septic systems are “decommissioned” by the year 2010, thus closing the environmentally negative loop forever. The State Government have committed well over $1 billion to this program.
You should enquire with the Water Corporation in your local area for the latest information on infill timetables and intended future capacities. You will find them very helpful and knowledgeable.