In general, a typical RO system wastes about 7.5 to 11.4 liters of water for every 3.8 liters of purified water produced. To put this into perspective, this means that for every liter of purified water produced, 2 to 3 liters of water are wasted.

This is because the RO process separates the purified water from the impurities, and the impurities are flushed out as waste water.

To utilize this waste water in the best way possible, there are several ways you can consider:

1. Collect the waste water: Install a holding tank to collect the waste water and use it for non-potable purposes like washing clothes, cleaning floors, and watering plants. This can help you reduce your water bills and conserve water.
2. Connect to a greywater system: A greywater system can be installed to treat and reuse RO waste water for irrigation, toilet flushing, or other non-potable uses.
3. Use it to flush toilets: RO waste water can be used to flush toilets, as toilets don’t require treated water. By doing so, you can reduce your overall water consumption.
4. Recharge groundwater: RO waste water can be used to recharge groundwater by directing it to recharge wells or spreading it on the ground. This can help to replenish the groundwater levels and improve the availability of water.

It is important to note that the RO waste water may contain impurities and pollutants, so it should not be used for drinking or cooking without proper treatment.