Our 3-stage compact RO system is a new type of aquarium filter. The water after it has been passed through an RO system has a reduced pH*. It is an excellent source to prepare appropriate conditions for aquatic organisms. 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. This reverse osmosis water filter, like all direct flow reverse osmosis water filters, 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. Our aquarium filter is factory tested and ready to use with connection hardware, tubing and instruction manual, all of which is designed to make installation and maintenance quick and easy without the need for a plumber. It is offered as a complete set with filter cartridges, RO membrane, additional accessories and valves to prevent the membrane from becoming dried out.