Water Sieve doesn't care polluted water's temperature.

Thats not a bug, It intended behavior. Sieve has a fixed output of 40°C. It does not matter if you put in -50°C or +99°C polluted water. The output will always be 40°C. Thats how it works at the moment. Deal with it, because its not changing very soon i suppose.

The sieve is great for destroying heat. Lead the cool polluted water through hot areas like your power plant to get it to 50-60 degrees, then use it as coolant in refining metal, then send your 100 degree water through the sieve and watch 60 degrees of pain just fade away.

It IS bug. If cheaters and bug-users wanna cheat - they have sandbox mode, just spawn hydrogen ice and it will kill extra heat, or use hundreds of other ways how to get rid of heat in sandbox mode, but in normal game mode second law of thermodynamic must work without such buggy exceptions.

It isn't logic. First i used this bug to cool polluted water which is coming from Thermo Aquatuner system but now it isn't funny anymore because game is easier.

if Klei fixe this, it will be cool and more logic.