Our compact 4-stage RO reverse osmosis system is a new type of aquatic RO filter designed for those who don’t have the space for a bigger unit. This system is equipped with two pre-filtration stages. The first is a sediment cartridge made from spun polyester. It effectively reduces and removes sediments including sand, silt, dirt, rust, etc. The second is an in-line cartridge containing granular activated coconut carbon which is designed to reduce and remove chlorine and dissolved organic substances. The main filtration takes place on RO membrane, which reduces and removes 96-99% of all impurities from water. Waste water is poured into the drain. The final ‘polishing’ stage is provided via mixed-bed ion-exchange resin. It consists of a carefully blended mixture of virgin raw materials, strong acid cation and strong base anion resins. This reverse osmosis water filter does rely on you having a strong mains water pressure. Please do not buy this item if you do not have a good water pressure. This unit operates best at input water pressures of between 40psi (3 Bar) and 60psi (4 Bar). We would suggest that this is not suitable for use with gravity-fed cold water systems (where the water is stored in the loft). Normal UK water pressure should start from around 3 bar or above.