Combined sanitary drains

A combined sanitary drain is a private sanitary drain which connects two or more properties to one common Urban Utilities sewer connection point. The first property on the combined sanitary drain will usually have the Urban Utilities sewer connection with a private drain running through this and neighbouring connected properties.

Is my property on a combined sanitary drain?

To find out if you have a combined sanitary drain on your property, phone Council on 07 3403 8888 and ask to speak with Plumbing Services. Copies of the sanitary drainage plan for the property and/or adjoining properties may be available for purchase from Council.

Maintenance responsibilities

Combined sanitary drains are not owned by Council or Urban Utilities. Ongoing maintenance is the responsibility of the owners of the properties serviced by the drain. Each owner must ensure that the section of the combined sanitary drain located within the boundaries of their property complies with the requirements of the Plumbing and Drainage Act 2018 s70, and is kept in good condition and operating properly. Any defects that occur in the combined sanitary drain must be rectified by the owner of the property that contains the defective section of a drain. A permit must be obtained from Council before repairs are carried out.

How do I come off a combined sanitary drain?

Before deciding to come off a combined sanitary drain, the property owner should find out where their property is on the drain. Where there are other upstream properties connected to the drain, the property owner wishing to disconnect will be required to provide a new sewer connection to those properties as well as their own. For further information relating to new sewer connections contact Urban Utilities on 13 26 57.

Combined sanitary drains and plumbing assessment

How an application for plumbing and drainage work is assessed depends on the nature of the work, whether a development approval is required and the apportioned fixture unit loading for the lot(s). 

The discharge capacity of a combined sanitary drain depends on its size. For example, a 100mm diameter drain has a discharge capacity of 165 fixture units at minimum fall.  This is the maximum volume of wastewater that the drain can handle.  Council equally apportions the maximum fixture unit loading across each individual lot that the drain passes through. This ensures future development is accessible for all lots.

Where a development approval is required, it is likely the applicant will be required to come off the combined sanitary drain.

For all other applications, if the proposed work is above the allowable fixture unit loading for the lot, Council will issue an Information Request to the applicant requesting either revised plans indicating a reduction in the number of fixture units or to come off the combined sanitary drain.

If the proposed work is within the allowable fixture unit loading, Council will require the applicant to either replace the drain boundary to boundary on the lot or come off the combined sanitary drain. Where the proposed work is for alterations to existing plumbing and drainage, Council will offer an additional option for the applicant to provide CCTV footage demonstrating that the drain is in good condition. 

Combined sanitary drains are required to remain operational for all lots while the plumbing and drainage works are underway.

When coming off a combined sanitary drain, a new sewer connection will be required for the lot and all upstream lots. This process is undertaken with Urban Utilities.

More information

For more information, phone Council on 07 3403 8888 and ask to speak with the Plumbing Services Assessment Team.

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