Mekanism

With Mekanism installed, water keeps its grade in its pumps, pipes and tanks, and its Rotary Condensentrator turns water vapour back into Pure water.

Supported versions

NeoForge on Minecraft 1.21.1, with Mekanism 10.7.19, and Forge on Minecraft 1.20.1, with Mekanism 10.4.16. Mekanism has no build for any other loader or Minecraft version, so they ignore it.

Electric Pump

The Electric Pump takes the grade of the water it pumps, the same as a bucket would. A pump in the sea fills up with sea water, and one in a swamp with Dirty water.

A pump holding one grade leaves water of another grade where it is, so two grades never mix in its tank.

Rotary Condensentrator

Water condensed from water vapour comes out Pure, whatever it was before. Turning sea water into vapour and back is a way to make it drinkable, at the cost of power.

Pipes and tanks

Water keeps its grade through Mechanical Pipes, Fluid Tanks, the Dynamic Tank and the Portable Tank. Water of different grades stays apart.

How grades are worked out is on the Water Purity page.