I would like to start by saying that I don't like that I can't collect water from real sources without mods. I would have added an additional water type, so you had "Dirty water" taken from any source, "boiled water" that you could drink but it might make you sick, and "clean water" something that had been filtered a little better so that it would not make you sick. and then the "purified water" that raises your stats better. Then the dew collector could have given you "Boiled" or ""clean" water but at a very slow rate, with no raise in the heat map.
Given the direction water is going, I suggest either:
Make the current dew collector not raise the heat map but give "dirty" water that still needs to be cooked.
Or
make a second model for the dew collector, one with a "campfire" or other such item attached to it or add a "mod slot" that adds a device to "Boil" the water.
Make the current one give dirty water that still needs to be cooked to be drinkable but doesn't raise the heat map, make the other an "advanced" dew collector, or something like that, that requires fuel to boil the water and make it drinkable on the spot but raises the heat map.
This way making drinkable water still raises the heat map like it used to but in a more logical way, and also still requires fuel to make drinkable water like before.