i'm using hydro one membrane series. 8 years still running without issues. automatic backwash. abit expensive than regular bacfree rocket eh series i think.

http://www.hydro1.com.my/

use sand cukup la. sand outdoor filter + boil water inside. kau tim.

my factories got deionized and another got RO. 1 more also got soft water.
i honestly tell u from an experienced person dealing with water products, sand filter + kettle is the best dirnking water u can get la.