There are lots of Aquarium filters and filter material one could use to pre filter one water supply with.
I have to pre filter.
I use rain water and melted snow (no running water here)
the straight rain water leaves a film that plugs the filter very fast (cpl weeks)
I also notice that the filter slows down cuz I dont use much drinking water.
apparently, the solids? dry on the filter and negate the proper function.
mostly because I don't use much and don't keep the filter chamber full.
that allows the surface of the filter, to dry out, and next time I add water, its very slow.
If I clean the filter, and back flush it, the water filters quite good.
but if I let the top chamber stay dry, next batch of water is not so fast.
even in my buckets, I can see a film from rain water.