It depends on your application and your type of water.
OxyAzur is a chemical-based water treatment solution. As effective as it is at eliminating bacteria, viruses, moulds, spores, fungi, and algae, it cannot filter solids out of the water. If you need to remove unwanted solids out your water, such as certain minerals or dissolved solids, or even just make sure that no insects and residue get into your home, we would recommend the use of water filters in conjunction with OxyAzur.
If you are just using the water to flush toilets and to shower with, then there will be no need, depending on the prior condition of the water. A good rule of thumb is: If the water in your tanks is clear to the eye then you can use OxyAzur without filtration systems.