Has anyone replaced their old shower mixer (11 years old) with a new sleek one. I am renovating my bathroom and I just want to change the look and the cartridge as well. I believe that I just have to use the same valve or what they call t-piece abroad. I was in touched by one of the plumbers and asked if the shower mixer I bought would work. He said that it would not but did not give me any of his opinion of what would work when I asked.