Callidus Swedish operations started in 1949 with the production of oil burners. The range was supplemented for a while with the sale of plumbing parts and in the late sixties with water treatment products, which today make up the bulk of sales. Today, Callidus market leader in water treatment, with over 500 dealers across the country. Callidus subsidiary in Finland started in 1969 with the oil burner as the main product.