Tritium isn't really a "separate chemical" but rather an isotope of hydrogen. Since water molecules are made of hydrogen and oxygen bound together, there is no simple way to remove the radioactive hydrogen by itself. The current best methods, from what I'm seeing online, involve separating the hydrogen and oxygen atoms into gasses and then processing out the tritiated hydrogen molecules. Apparently, it's expensive and only about 85% effective.
https://agrdailynews.com/2015/07/01/how-to-remove-radioactiv...