You need to completely reset / rethink your plan. It just doesn't work that way.

Start with "what exactly are you trying to accomplish?" "Why are you doing this?"

Do you want soft water?

Do you have well or municipal water? Are you trying to remove chlorine?

Do you have a specific contaminate you are trying to remove (lead, nitrates, sulfur, etc).

If you don't target your question better - you will discover the only thing that will get filtered is the money out of your bank account.