Liquid dynamics are off when different types mix

Whenever two liquid types come in contact, e.g. polluted water and regular water, we get very odd behaviour, like in this situation:

There is maybe 200 grams of fresh water on the tile under the storage compactor, yet magically it's preventing 20 tonnes of polluted water from spreading.

A similar problem exists when a mixture of polluted and regular water is flowing from a dug out "staircase" shaped ground. This causes large amounts of one liquid type to be held back by a small amount of the other type.

I realise this is probably due to how the liquids are modelled, and because the different types don't mix. I would like to suggest, that in particular for water vs. polluted water, the way this is modelled is changed to just having "water", of which a certain % is polluted. The color can then become more yellow depending on the % level of pollution, and using a liquid filter you could split it up into clean water and polluted water just as we do now, they would just act like one body of fluid.