PEACHTREE CITY, Ga., Nov. 16, 2015 /PRNewswire/ -- Rinnai, the number-one selling brand of tankless water heaters in the U.S. and Canada, has signed on as an official sponsor of FIFA Club World Cup 2015, being held December 10 - 20 in Japan. FIFA Club World Cup, the largest international men's association soccer competition, is one of the most watched events organized by the Federation Internationale de Football Association (FIFA).