I am having a problem with a tankless water heater that is less than a year old. The manufacturer is blaming the plumber for installing galvanized dielectric unions in line with the copper pipe. They are voiding my 10 year warranty. I am in the city, with city water that comes mostly from wells and also have a water softener installed. Does it seem feasible that corrosion from these fittings could have caused a problem in less than a year?

