Why Do Reverse Osmosis Systems Waste Water?

Why Do Reverse Osmosis Systems Waste Water?

A reverse osmosis (RO) system is installed for the sole purpose of providing clean water by removing all impurities. The impure water containing the contaminants is called “wastewater,” and the pure and filtered water is sent to your tap. If you want to know why a Reverse Osmosis system wastes water and how you can reduce wastewater, you are at the right place.

A Reverse Osmosis system removes waste water because it is hazardous to health. Its job is to separate contaminants from water by flushing out the wastewater. This wastewater is unsafe as it contains all the harmful chemicals and substances removed by the RO system to purify the water. The amount of water wasted will depend on the design and fitting of the RO system.

The general workings of an RO system compel them to waste water. The average amount of wastewater an RO system produces is 4:1. This means that between 3-25 gallons of water are wasted to produce 1 gallon of clean RO water. Let’s look at how you can save some of this precious water and find out some of the reasons behind why RO systems waste water.

Read my comprehensive article about reverse osmosis.

Two Main Reasons Why RO Systems Reject Waste Water

Whatever version of an RO system you will use, there will always be leftover water that is flushed away and is not safe for drinking. Let’s take a closer look at why RO systems flush out wastewater:

1.   The system design

The RO system has a semi-permeable membrane. This membrane is designed to separate the harmful contaminants from the water and send the clean and purified water through your tap. The membrane concentrates the water that is high in contaminants that cannot pass through it, on one side, while the other side holds the clean and contaminant-free water.

The concentrated water, containing the contaminants, is then flushed out and is called wastewater. As a comparison, you could argue, this is similar to washing your hands underneath an open tap and some water has to be “wasted” and flushed down the sink.

 2. Protecting the membrane

RO systems have filters with a 2–3-year lifespan but are a bit more expensive than normal filters. They can become inefficient, over time, due to the buildup of minerals like calcium and magnesium. When this happens, the overall process of purifying water can slow down.

RO systems are designed to flush out the filters to maintain and protect them from time to time. This flushing out of salt also contributes to wastewater.

This video explains why reverse osmosis filters waste so much water.


How Can You Reduce Waste Water from Your RO System

Your RO system will produce waste water due to the way it is designed. However, you can take some steps to ensure there is no extra wastage and use this water elsewhere:

1.   Regular maintenance

While an RO system doesn’t need a lot of maintenance, you can’t really install and forget about them either. You need to maintain them and also keep a check on them from time to time.

You need to know how the RO system works and what kind you have installed. The best RO systems out there pass water through five stages to purify it. This means that there are five filters that are designed to clean out different kinds of contaminants.

The RO membrane is also a vital part of the system, and it can last up to three years. However, the other filters can wear out within a year and need to be cleaned out and replaced properly.

You should also clean out the filter with a hydrogen peroxide solution once in a while to ensure the housing gets a nice clean. This will ensure your system stays in shape and lasts longer.

Read my article about reverse osmosis system maintenance.

2.   Appropriate water pressure

Low water pressure can lead to more water being discharged from your RO system. The ideal water pressure range for RO water to work in optimal conditions is 35-40 PSI.

You can check the pressure in your home by looking at the reducing valve. If the pressure is low, you can increase it to maintain the good efficiency of the RO system and to reduce water wastage.

What Are Zero Waste RO Systems, and Do They Work?

Reverse Osmosis water purification systems waste gallons of water to produce a small amount of pure water, leading to the invention of “zero waste” RO systems. Zero waste systems push the concentrated water or wastewater back into the hot water plumbing, so nothing is wasted.

It does this with an additional electrical pump that pushes the wastewater back into the plumbing, and the system is installed to prevent this wastewater from going back into the RO membrane and damaging it.

The zero waste RO systems may be good at reducing or eliminating wastewater. However, the contaminated water can make its way to your kitchen sink, and you can end up washing hands, dishes, and vegetables with it.

This water is filtered through carbon filters and doesn’t have harmful contaminants. However, it still has a high concentration of salts such as calcium which can damage your skin, appliances, and dishes.

Read my article about the sustainability of reverse osmosis.

Frequently Asked Questions

Can reverse osmosis ruin water quality?

Reverse Osmosis systems purify water through a membrane with very low permeability that does not allow most contaminants to pass through. The resulting water is pure and contaminant free. Reverse Osmosis systems may need help from other filtration systems to fully purify water of all possible contaminants.

Is boiling water better than reverse osmosis?

Boiling water can remove impurities like magnesium and iron. However, only Reverse Osmosis paired with other filtration processes can remove all contaminants in water, such as bacteria and sediments.

Learn more about boiling reverse osmosis treated water.

How long can you store RO water for?

You can store RO water for up to 2 years, provided you keep it in an airtight container and in a cold dark place. When the water is exposed to air or light, it should be drunk between the next 2-3 days.

Read my article about storing reverse osmosis treated water.

Final Thoughts

RO systems produce wastewater because they are designed to separate the contaminants from the water. The contaminant-rich water is simply flushed away because it is harmful to health. There are ways in which this waste can be reduced, and we hope our article helps you take those steps to stop the extra waste of water.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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