RO water purification principle, also known as RO reverse osmosis principle, It’s a popular way to purify the water through the international. After the filtration of the raw water (physical method), this machine adds no additional compounds to produce the pure water which can be drink directly by human. (also known as a terminal water purifier) Use the Tap water which satisfy ( 2001) as the raw water. The pre-treatment : the water goes through 2 activated carbon filter(one is granular active carbon and another is Sintering activated carbon) and 1 PPF Solution spray filter. Then use the pressure to make it goes through RO membrane, the water will goes through Silver activated carbon (the material is shell) to adjust the PH of water. It will make the final water feels a little sweet.