1)The principle of 2-step reverse osmosis(RO) device is to adjust the PH-value of water through first step device, then high pressure pump transfers liquid into the second step device to treat, and get the cleaned water at last.

2)The desalt ratio of the 1-step system is over 99.5%. It doesn't need ion-exchange treatment and can be up to the standards of bottled drinking water(Conform to GB17323-1978)