This is my second Rowenta. I had the first one for about 10 years.  This one is less than a year old. The edges of the sole plate are rusting...and I live in Arizona. The water here is very hard and this iron can't deal with it. I have to self clean every time I use it. I am constantly having to rewash clothes because of the residue left by the iron, especially dark clothing. They say not to use distilled water. So what to do?