Kangaroo Island locals say it is "disappointing" and "stressful" that their properties will not be connected to a desalination plant that opened in Penneshaw last week.

With a capacity of two megalitres a day, the plant has provided clean mains water to around 700 local homes and businesses for the first time. 

However, local Alan Thomas said his property at Baudin Beach, which he bought two months ago, was not connected to the plant.

"The real estate agent said there was no reason why we wouldn't be connected," he said.

"Both our neighbours on either side of us are connected and the pipes go straight past the front of the house.

"The previous owner didn't put in an application when they were calling for initial applications, so the house wasn't connected when the first round of connections were done."

Mr Thomas applied to SA Water in November, but it emailed him the next day saying the plant had "far exceeded" its expectations so "no further connections can be provided".

Mr Thomas said he then called SA Water.

"Their response was to check back in three to six months," he said.

Not taking running water for granted

Fellow local Marty Kay bought a house at Cygnet River in early 2022 and applied for a connection to the plant shortly after.

SA Water emailed him in August, explaining how it would activate locals' connections, but Mr Kay said it called him a few weeks later to say he would not be connected.

Mr Kay said he spent just over $3,000 last year on getting truckloads of water delivered, and this year would be similar. 

"We have one dam and 100,000 litres of rainwater storage [for] our shearing shed workshop and housing," he said. 

"We've got around 300 sheep and three horses, and a family of five, so we are pretty high users of water."

He said SA Water called him on Friday to say it would begin the process of connecting his house in February,  but that meant his property still would not get water until a few months after that. 

He said he did not "have complete faith" his property would ever be connected, so was working on a plan to connect to a neighbour's supply and pay them for his water usage.

"The anxiety sometimes when you don't have that access to water is quite a strange feeling," he said.

"It's a real balance between, 'Do I ring the truck again and spend another $350 or hope that it rains?'

No plans to expand

Kangaroo Island Council Mayor Michael Pengilly said SA Water should consider expanding the plant "fairly quickly".

"We've had a very dry year on the island … particularly on the south coast, there's a lot of farms and things that are going to have to have water carted to them," he said.

"There's only two places the water can come from, the desal plant at Penneshaw or Middle River Dam."

SA Water also installed 420 fireplugs around Kangaroo Island to give emergency services easy access to water.

The Middle River Reservoir ran out of water during the 2019/2020 bushfires.

According to the state government, the bushfires burnt around 38 per cent of the island and 83 per cent of that was burnt at a high to very high severity.

In a statement, an SA Water spokesperson said it fulfilled around 700 connection applications, more than double the expressions of interest it received.

It said "a small handful" of customers were on hold and that there were currently no plans to expand the plant's capacity.

"[However], the facility is scalable with any required future expansion subject to funding approvals," a spokesperson said.