The corrosion resistance of stainless steel does not mean that it will not be corroded. 
Water will corrode the metal, and impurities in the liquid will also corrode the metal. 
In the long-term transportation process, the passive film on the surface of the steel will be continuously destroyed, thereby corroding the stainless steel tee.
In our daily process, we must understand that stainless steel tee has corrosion resistance, but it is not corrosion-resistant. In the process of use, especially the tee that has been used for a certain number of years, we must check it in time to avoid greater damage.