Reverse Osmosis Water Waste: How to Reduce, Recycle and Reuse RO Waste Water

There is no tint of doubt about RO system’s ability in purifying water. But, it’s biggest drawback i.e RO reject water is a headache to every household using the system.

An average RO water purifier wastes around 80% of its input water supply!

You need to look closer!

Water is one of the most important natural resources. We are going through a phase where scarcity of water is suffocating common folks. Does that mean you shouldn’t buy an RO purifier?

Or is there a way around?

Of course, there is. We have written this ultimate guide on RO waste water, to tackle this issue. If you pay attention, you will learn the following:

  • How to reduce waste water in the RO system
  • 7 Ways to reuse and recycle RO waste water

Why RO Waste Water is created?

The majority of Indian citizens are concerned about the quality of water supplied through municipal and borewell systems. These concerns are related to the increasing levels of pollutants and microorganisms in borewell systems and the diseases that they cause.

Due to these reasons, more and more people are switching to water purifiers for a cleaner supply. One of the most commonly used methods, for this reason, is Reverse Osmosis (RO).

But here is something that you probably didn’t know:

  • The RO membrane technology filters impurities by using additional water.
  • The additional water cleans the filter and is then discharged, causing water wastage.
  • A few research studies found that RO purifiers discharge three times more water than what is purified. This means the purifier is wasting approximately 80% of the water coming to the machine.

What’s the Danger of using RO Reject Water?

According to water experts, the discharge water rejected by RO filters is a no-go zone. This wastewater contains high contents of total dissolved solids (TDS) which makes the water undrinkable. And, in some cases, this water also becomes unsuitable for daily chores.

Moreover, the amount of inorganic salt and organic matter in this discharge is very high. That only adds up to why the filtered wastewater is unusable.

Water with a high TDS level often contains a foul odor and taste, making it unpleasant for the drinker. Moreover, it has also been linked with some serious illnesses like stunted growth, reproduction failure, and more.

Using wastewater for daily chores may cause stains or leave salt residues.

7 Easy and Tested Ways to Reuse RO Waste Water

If you have installed an RO system at home, office, or elsewhere, we recommend storing the discharge in a bucket. You can then re-use it in some simple ways to reduce the amount of wastage. After all, every little droplet counts!

1. Mopping

One of the easiest way to recycle RO waste water is to use it for mopping

You can use the RO Reject Water for your daily chores like mopping and scrubbing the floors. However, make sure to mix the wastewater with some fresh and clean water. High TDS and salt content can leave stains behind after drying.

This sticky or greasy residue may become unpleasant. However, you can counter this problem by diluting the wastewater.

2. Car Wash

Reuse RO water waste for washing your car

Did you know washing your car takes up approximately 14 liters of water? A great way to save up on freshwater is by substituting it with the filter discharge. All you need is a bucket or reject tank, and your car will have its much-needed wash!

3. Water your Garden

The most convenient and effective utilization of the expelled RO water is using it for gardening. Vertical gardening is a newer concept and a popular trend these days. You can use your balcony or terrace wall to grow plants.

The high nutrients and minerals in the water can help your plants bloom and grow. Although, this is preferable for urban areas only where the municipal water TDS levels are typically lower.

Use a watering can or bucket to store the expelled water. Use this discharge on plants stored indoors and outdoors. However, we recommend doing a trial at first to make sure there are no adverse effects.

It is an essential measure considering how each plant reacts differently. Here are some more tips to keep in mind:

  • Get a TDS measure of the expelled water. The permissible irrigation and farming TDS levels are 2100 PPM.
  • Moreover, the sodium percentage should also be measured to prevent long-term harm.
  • High sodium can affect the texture and structure of the soil, impacting the plant yield in the process.

4. Dish Washing

Since most individuals install the RO filters in the kitchen, what better place to utilize the wastewater in than at the sink?

The average faucet runs at 2 gallons/minute which often keeps running during dishwashing. You can do the math and find out the amount of wastage in the process!

RO wastewater can work as the perfect alternative to reduce this amount. You can wash your utensils or pre-soak them after every meal. Soaking will help to remove crumbs and food stuck on the plates. Moreover, it will also help to eliminate the grease.

You can then clean the dishes with soap and regular tap water. We do recommend a freshwater soak in the end to prevent salt deposition. After all, we don’t want you to ruin your precious china!

5. Toilet Flushing

Use RO reject water for flushing your toiletsWhile it is a complete no-no for bathing, you can use the filter waste for toilet flushing and cleaning. Flushing takes up 6 to 7 liters of water which directly goes down the drain. It is a massive amount considering the number of times we flush daily.

You can limit this normal tap water wastage by using the TDS water for flushing. Pour it down the cistern of the toilet seat to utilize it efficiently.

Additionally, you can also dilute it with regular freshwater to clean porcelain tiles and the toilet seat.

However, as mentioned above, salt deposits and discoloration are common consequences. For this reason, it is crucial you closely monitor for any signs. To avoid damage, we recommend using this method for periodical clean-ups only.

6. Bathing Pets

To an extent, water coming out of RO can be used for bathing petsGot pets at home that you regularly bathe? Did you know you could utilize RO wastewater instead of discarding it?

Few pets are often sensitive to hard water. For this reason, we suggest diluting it with ordinary tap water. Also, make sure to towel dry the pets afterward gently.

7. Pre-Rinsing Laundry

Laundry washing typically uses a large quantity of water that goes to waste. An alternative to it can be using RO discharge for pre-rinsing.

Dissolved salts in this water can help to remove stubborn stains. However, bear in mind, delicate fabrics may not react well with high TDS water. For that reason, you can try diluting it 1 part discharge in 2 parts fresh water.

You can also use it to wash carpets, rugs, and curtains that aren’t too delicate.

How to reduce Waste Water in RO Purifier?

As a developing country, with limited resources of clean and pure drinking water, we are forced to opt for healthier options. In such a case, filters and purifiers become a necessity, with RO being the top choice.

Considering the rapidly vanishing sources of water, it becomes a moral responsibility to save water. Each droplet counts! Countries like India and Brazil are most susceptible to climate change and are experiencing prolonged droughts.

The foremost step is to install an additional tank that accumulates the discarded water. With the help of a pipe, you can connect the TDS water output to any appliance that can make use of it. Alternately, you can use it for your household chores.

We have already discussed many innovate daily hacks to recycle this water. But, here are some new and added ways to reduce the wastage.

  • Feed the discarded or wastewater into a 2nd RO unit. This method directly saves 20% of the waste, leaving you with remaining expelled water.
  • However, due to the high salt and organic matter content, the RO unit may experience scaling.
  • Another method is to use electro-dialysis, which uses low energy and is a cost-effective method to purifying water.
  • You can also install a permeate pump. The pump increases the efficiency of the Reverse Osmosis (RO) system, reducing the wastage by 70%. Make sure to purchase a system that allows for an additional pump to be attached.
  • An auto-shutoff mode or feature can help stop the drainage when the tank is full.

Can RO Waste Water be used for Bathing?

Due to the high level of impurities, we do not recommend the filtered wastewater for bathing. The high TDS level (above 200mg/liter) is a mark of the hardness of the water. RO filters remove this hardness by “rejecting” the water, giving you pure and drinkable water.

can ro waste water be used for bathing

Using this hard water for bathing can cause a number of issues:

  • High TDS in water can irritate the skin
  • The increased salt contents can lead to hair fall
  • Hard water when interacting with soap does not cause lather
  • The porcelain, shower head, and tiles will experience staining from the hard water.

However, bathing with such water is an individual choice. Research provides mixed evidence, with some doctors encouraging TDS water for bathing. According to them, your skin can absorb the salts and minerals, citing them beneficial.

They claim it to be as effective as using bath salts!

Hence, bathing with RO waste is a choice. However, in any case, make sure to dilute the water to prevent skin irritation and hair fall.


Can I divert RO reject water to 2nd treatment unit?

No, you can’t divert the reject water from RO to its inlet or to another RO system. Why?

The RO waste water already contains a high concentration of impurities and minerals. There is no use in feeding this high TDS concentrated water to the RO purifier once again.

Can I use RO wastewater for bathing?

It is not recommended to use RO water waste for bathing.

Will RO wastewater harm my plants and flowers?

Watering your plants and flowers using RO reject water is a good idea. But make sure that the water is not highly saline.

How much waste water does RO produce?

An RO system is notorious when it comes to producing waste water. For every 10 liters, it will produce approximately 7-8 liters of water waste. That means you will get only 2-3 litres of pure water from 10 litres of water from an RO system.


Many urban homes have started making the switch to RO filters for their daily consumption. It is a much-needed shift considering the increasing concerns regarding contamination and pollution. While RO purifiers contribute to water wastage, there exist numerous ways to cut back on it.

Recycle, re-use, or restrict – these three methods can limit water wastage to a great extent. By conserving the expelled waste, your eco-friendly move may help to save water for up to 4 lives.

Brands are continually working on bringing innovative technologies to control the problem of water wastage. In the meantime, we can follow these useful ways on how to re-use RO wastewater. The easiest solution always exists at home and even a small step that you take can have a huge impact.

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