Sediment, Softener, Charcoal is the common order to plumb them in. Water softener is a 10 micron filter in itself. If you are thinking of a portable softener that are designed for RV use, you need to keep in mind that you will have to be able to pour salt in the top of the unit and have somewhere for the water to go during regeneration. Most have an orfice that water just sprays out of. Personaly, I don't use a sediment before my softener, but I do have a 5 micron after the softener.