The Mid-West and South-West Gas Distribution Systems (GDS) is a distribution pipeline owned and operated by ATCO Gas Australia Pty Ltd (ATCO) (formerly known as WA Gas Networks Pty Ltd).

In 2011, ATCO acquired the GDS from the WestNet Infrastructure Group (formerly known as Alinta Gas). Alinta Gas was formed in 1995, when the Western Australian government restructured the state’s gas and electricity industries from the government owned monopoly (State Energy Commission of Western Australia) into separate businesses which were sold to the private sector. 

The GDS consists of a number of separate gas distribution networks covering Perth and the regional centres of Geraldton, Eneabba, Pinjarra, Harvey, Kemerton, Bunbury, Capel and Busselton. It consists of approximately 12,800 km of pipeline delivering gas to around 620,000 customers.

The GDS is connected to the Dampier to Bunbury Natural Gas Pipeline and the Parmelia Gas Pipeline.

The GDS was a covered pipeline and regulated by the Western Australian Office of Gas Access Regulation (OffGAR, now the Economic Regulatory Authority (ERA)) under the Gas Code. Under the National Gas Access (Western Australia) Regulations, the GDS is classified as a ‘designated pipeline’. This means that under the NGL (ss. 109 and 111) the GDS remains under full regulation and cannot be the subject of a light regulation determination.

The GDS is subject to full regulation by the ERA under the NGR. The GDS has been connected to the Dampier to Bunbury transmission pipeline since the mid-1980s.