The difficulty of filtering out tritium from water is that tritium oxide is water and not some solution or colloid. Tritium is an isotope of hydrogen and reacts

The difficulty of filtering out tritium from water is that tritium oxide is water and not some solution or colloid. Tritium is an isotope of hydrogen and reacts with oxygen to water, namely tritiated water. One way is distillation because the boiling point of tritiated water is slightly above that of normal water (101.5°C instead of 100°C), but this seems to be a lot more difficult than distilling alcohol.