A steam generator comprising a heating unit, a pump adapted to deliver a controllable flow of water from a water supply into the heating unit and an outlet for steam from the heating unit; the heating unit comprises a housing, a heating element disposed in the housing and a conduit for water and steam extending from the inlet to the outlet; the conduit includes a passageway extending in an elongate path in contact with or adjacent the heating element; wherein the housing comprises two portions releasably seamed together to provide a channel between the portions to receive the heating element and to provide the passageway.