Is Reverse Osmosis Water Wasteful?

Reverse osmosis (RO) water purification systems can be considered wasteful in terms of water usage when compared to some other water treatment methods. RO systems work by forcing water through a semi-permeable membrane to remove impurities, minerals, and contaminants. 

While they are effective at producing high-quality purified water, they can generate a significant amount of wastewater in the process. Here's why RO water can be considered wasteful:

Wastewater Production: 

For every gallon of purified water produced by an RO system, there can be a substantial amount of wastewater generated. The exact ratio depends on the system's efficiency and design, but it's not uncommon to have a 1:3 or even 1:4 ratio, meaning for every gallon of clean water, 3 to 4 gallons may be wasted.

Resource Intensive: 

RO systems require energy to operate, and they often use more electricity than other water purification methods, such as simple filtration or disinfection. This contributes to energy consumption and environmental impact.

Limited Supply:

In regions with water scarcity or drought conditions, the wastefulness of RO systems can be particularly concerning, as they put additional strain on already limited water resources.

Maintenance and Costs:

RO systems can be costly to install and maintain. The expense of replacing filters and membranes regularly, combined with the energy costs, adds to the overall environmental footprint.

A reverse osmosis system is 25% efficient. A washing machine and dishwasher uses electricity and hot water (which takes energy to heat) and WASTES EVERY GALLON OF WATER THEY USE. A reverse osmosis system is not nearly that wasteful – no electricity and no wasted energy with heated water.

Where does RO waste water go?

In reverse osmosis, there is cross-flow filtration through the membrane. The permeate stream (product water) goes to the storage tank, and the waste stream with all the contaminants and dissolved inorganics goes to drain (also called concentrate stream or RO reject water

How much water does RO filter waste?

An average RO purifier wastes approximately 3 litres of water for every 1 litre of purified water. That means only 25% of water is purified and 75% of water comes out as waste.


Your reverse osmosis system will use 1% of your annual household water usage annually. The average family RO will move roughly 12 litres to the drain every day. If you compare this with a shower which is the biggest consumer of water in your home with the average shower using 40-60 litres per shower. Or every time you flush your toilet up to 10 litres can be used. As RO water is only used for consumption the amount of waste is minimal.

Sign in to leave a comment