Every second person is marketing water filters nowadays in Kuwait, specially being sold to Expats.
Coolpex - KD 130/- plus
WaterLifetech - KD 85/- plus
Ali Alghanim Sanitary Showroom in Shuwaikh sell there brand for KD 80/- plus
All of this are made in china & have membrane from USA and quality is almost similiar.
If you bargain properly, you may get it for KD65/- too.
Almost all of them are promising a warranty on product and try to give extra maintenance free of charge, if you bring another customer.