The Adelaide desalination plant will hold a free community open day on Tuesday 21 October to demonstrate how it turns seawater into drinking water.

Built to underpin water security for metropolitan Adelaide, the Lonsdale plant has been operating since 2011 and is able to produce 100 gigalitres each year.

According to Environment SA the Adelaide desalination pant has one of the smallest carbon footprints of any desalination plant in the world.

It says independent reviews of the plant's environmental impact show that it has caused no harm to the environment, with continual monitoring the environmental health of Gulf St Vincent.

The open day will offer guided bus tours of the site and visitors can also enjoy its native gardens and walking trails and the Kauwi Centre for Water Exploration.

This event is free to attend but bookings for one of the three 90 minute sessions are essential via Eventbrite.