- RO 6-stage reverse osmosis system, the type installed under the kitchen sink. This is what you see in the picture: • The 3 blue filters below: are the primary stages ◦ PPF: sediment, sand, and rust filter ◦ UDF: granular carbon filter that removes chlorine and odor ◦ CTO: block carbon filter that softens taste and protects the membrane • Above them: the pump (motor), the pressure gauge on the left, and two horizontal filters - one of them is Post Carbon for the final taste, and the other is the main RO membrane that removes heavy salts. • On the right: the large white tank for storing purified water, and the stainless steel faucet that is installed on the sink. This system is excellent if your tap water has high salinity or a strong chlorine taste in Riyadh. It provides drinking water close to bottled water. It requires replacing the three filters below every 3-6 months, and the upper membrane approximately every two years depending on usage.