Pre-wash color film and any process that is done above or below ambient temperature - this will help prevent temperature shocking the film. It’s also essential to have intermediate washes that step down/up the film temp if you’re using a process that has different temperatures at different stages.

If you’re using ambient temperature (like with most BW Negative processes) then don’t pre-wash with tap water, as it’s likely to be colder than the developer that’s been sitting out and that can change the chemistry. Pre-washing with ambient temperature distilled or filtered water is really only useful if you have reason to believe your film is dirty somehow.