Two-stage reverse osmosis:

The original water (tap water, surface water, underground water) is sent to pretreatment system by adding pressure to be filtered roughly, then to be filtered by sophisticated filter, and the water is transmitted to primary reverse osmosis by one-stage high pressure pump to be filtered, then the water is add pressure again by secondary high pressure pump and sent to second reverse osmosis system to produce the product water, this source is called two-stage reverse osmosis.

Raw water conductivity>500us/cm; Purified water conductivity: 1_10us/cm