HaloSource has completed an initial public offering on London's AIM exchange for small companies, selling $80 million in stock.

The deal raises $50 million before expenses for the Bothell-based company, and $30 million for existing shareholders who sold some stock.

HaloSource, best known for water-purifying technology built into filters or dispensers sold by other companies, said it will use the proceeds to support its expansion plans, including construction of additional manufacturing plants.

The company said its shares are expected to start trading Monday. Its initial market capitalization, based on the placement price of 135 pence ($2.14) per share and about 73.8 million shares issued, will be about $158 million, HaloSource said.

Chief financial officer James Thompson said HaloSource raised its last three private rounds of financing in London, so it made sense to go public there.