When it is used as a filter, it is not uncommon for the manufacturer to spray a PVC coating to make it stronger and last longer.
Mgbe a na-eji ya dị ka nzacha, ọ bụghị ihe ọhụrụ na ndị nrụpụta na-agba ihe mkpuchi PVC iji mee ka ọ sie ike ma dị ogologo.