Don't even think of tossing that TP filter down the drain (besides, they are the consistency of a block of wood after use), Dad used to set them on fire and use them to help burn weeds. I seem to recall the darn things would burn for most of an hour.
OK... so, how often do you change these things?
And, just how clean is or isn't it? I don't think the towel filters would be very good. The towels are not dense and very porous compared to the commercial tp rolls.