How To Use Ro Waste Water

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Although the RO system helps in purifying water, it happens to waste a lot of water during this process. For purifying one litre of water, the RO wastes about three litres of water. That is too much water. Isn’t it!

Are you looking out for ways to re-use that water? Do not worry! We are here to help you out in this matter.

In this write-up, we shall discuss the different ways to use the rejected water. We shall also learn about the effective ways to store the RO waste water.

Let us get started with the discussion. Before that, we will learn why you should re-use the RO waste water.

Why Should You Re-Use RO Waste Water?

We all know that the RO waste water is unfit for drinking. RO water purifiers purify the water and remove all the impurities and pollutants in it. As a result, the water is clean, free from life-threatening microorganisms that cause diseases, safe and tasty.

However, the only drawback with this process is the excess water wastage. This percentage of waste water may vary for every RO purifier model.

On average, an RO purifier wastes about three litres of water for purifying one litreThat means it purifies only 25% of water, whereas 75% gets wasted.

The RO purifier uses a membrane technology that demands additional water to filter all impurities. Consequently, it discharges the waste water outside after cleaning.

As mentioned earlier, this rejected water contains high-level dissolved solids and impurities. Hence, it is unfit for drinking and bathing. However, you can re-use this water for other activities without worrying about wastage.

Let us learn about the various ways to use the rejected water. But before that, there are certain things you need to keep in mind. Below are the essential points that one needs to be mindful of:

What Are The Things to Consider Before Using the RO Waste Water?

The primary point for consideration is the TDS factor. Even before you decide to use the RO waste water, it is essential to determine its TDS level. If the TDS level of the rejected water is too high, it is not suitable for re-using it for other purposes.

If the TDS level of the RO waste water lies between 1500-2000, you can comfortably use it for various applications, as mentioned below. Do not use it for drinking!

What Are The Easy Ways to Reuse RO Reject Water?

You can effectively use the rejected water for various applications. Below are some of the ways you can try at home:

Application 1: Wash Your Car

Do you want to make the best use of the RO waste water? Try this, and you will love it for sure. You can wash your car using this water. Yes, you heard that right! Let us try to do some simple calculations.

For a single car wash, you may need about 14 litres of water when using a bucket. It would jump to about 75 litres when using a hosepipe.

But, if you use the RO waste water to wash your car, how much quantity of water would you be saving! Doesn’t that sound wonderful! All you have to do is store the rejected water in a water tank or bucket and use it every time for your car wash.

You may say, what about the TDS level? Well, here is the answer for you.

If the TDS level of the water falls in the range of 1200 – 1500 PPM, it is absolutely safe to use it for washing your car. If the TDS level is a little higher, you can still use it, provided you dilute it with normal water. This will ultimately reduce the TDS level in the waste water.

After you finish washing the car with the rejected water, immediately you can use a bucket of clean water to wash it. It is advisable if you want to get rid of any salt deposits on the vehicle.

Application 2: Utilize for Watering Your Plants or Home Garden

We all have plants at home. Don’t we! So can utilize the RO waste water to water your plants. I know you are a little surprised, but that is true. Whether you have a garden at home or small pots of plants, you can happily use this water for them.

Let us come to the TDS level of the water.

The required TDS level for gardening or irrigation use should be up to 2100 PPM. This level is permissible. However, you should also for the Sodium percentage in the waste water. It is mandatory that it should be less than 60%. The presence of sodium content in higher quantities will decrease the soil porosity. Eventually, the soil will no longer be fertile for irrigation.

There is always a plan to get started on such things. You may try watering a few plants with the rejected water and monitor for about 15-20 days. If you notice that there are no negative effects on the growth of the plants, then you can continue doing it for the rest of the plants. This experiment keeps you on the safer side. 

Remember that the plants may respond differently to this change. Observe the responsiveness of each plant to the RO waste water.

Application 3: Dish Washing

What if I told you that you could use the rejected water for dishwashing? Oh yeah, you heard that right, and I am not kidding on this. Using RO waste water for washing your dishes is yet another effective way to reduce wastage. All you have to do is store this water in a water tank or bucket and use it every time for washing the utensils.

You can collect the RO waste water by placing a bucket near the RO purifier. This tip will help you in saving water. Use this collected water to soak the dishes for a while. This will remove any food particles stuck to the dishes and prevents them from drying. Now, you can use fresh water to clean your utensils. It is a thumb rule to use only clean water for washing.

Application 4: Floor Mopping

Floor mopping is another crucial household chore that requires dozens of gallons of water. If you want to save on this, you can make use of the RO waste water. This way, you can use the saved clean water for more important purposes.

Let us talk about the water savings. If you are living in a big house, you would probably need several litres. That is quite enormous. Instead, use the rejected water for mopping the floor and save big on the clean water.

The TDS level of waste water for floor mopping should be up to 2000 ppm). If it more than the mentioned range, this is what you can do:

Dilute the reverse osmosis waste water with the same quantity of tap water. Using plain RO rejected water may leave stains and salt deposits on the floor, eventually damaging it.

Here is another thing you can do to minimize the chances of stains or salt deposits. Use the RO waste water to mop the floor on alternate days.

Application 5: Pre-Rinsing Laundry

Washing your laundry load with the RO waste water would be a better idea. No matter how efficient a washing machine might be, it still uses a large quantity of water. To prevent water wastage, you can use the RO discharge to pre-rinse the laundry load. This amazing tip works best for washing machine models like the semi-automatic and the twin tub.

But how to do it? You can collect the RO waste water into an overhead tank and use it directly in your washer.

Note that some delicate fabrics may be susceptible to damage because of the high TDS level in the water. To prevent this, dilute one part of waste water with two parts of fresh water.

You can also wash other not so delicate items like carpets, rugs, etc.

Application 6: Toilet Flushing And Cleaning

This application is the best way to make use of the RO discharge. Flushing and cleaning your washrooms consume a lot of water. Did you know that every time you flush the toilets, you are using about seven litres of water? Imagine how many litres you would be wasting for the multiple flushes in a day! You can cut this water consumption by making use of the waste water. The procedure is very simple. Pour this water into the toilet cistern for utilizing. Whenever you flushing, the rejected water gets down into the drain.

Let us talk about using the rejected water for cleaning the bathrooms. Again, dilute it with fresh water to clean the bathroom tiles, faucets, toilet seats, etc. Diluting the water is necessary to avoid discolouration of the items or deposition of salts on them. However, we advise you to follow this cleaning method periodically to avoid any damage.

Application 7: Sewage Pipe Cleaning

Another efficient way of using the RO waste water is cleaning the sewage pipes. These pipes in the kitchen or home may get greasy because of prolonged usage. The saline nature of the discharge water can help you to effectively get rid of all that.

For this task, dilute the RO waste water with a little amount of acid and use the mixture for cleaning. Additionally, you can use the rejected water to unclog the hard residual water in other appliances.

Can You Use RO Waste Water For Bathing? Is It Safe?

This is one of the most frequently asked questions by many. Also, many people often get into a debate on the same. Some argue that you can use RO waste water for bathing by diluting it with clean and plain water. Doing so reduces the salinity in the water. However, some do not agree with this idea saying that hard water should not touch human skin.

Their point is also valid because the RO waste water contains high hardness and it can be harmful to the skin. The possible consequences of using may include skin problems, skin redness, itching, irritation in the eyes, etc. Apart from that, it also causes hair fall.

To put a check to this debate, scientists even conducted some studies and got mixed responses or results from it. Some doctors suggest taking bath using some bath salts, as it is good for the skin. They claim that even humans absorb some salts and minerals through the skin, just like plants do.

If you ask us about our take on the same, this is what we would say. It is the personal choice of an individual when it comes to using RO waste water for bathing. If the person has no problem using the hard water, he can use it without any doubt. However, he or she needs to dilute it first before using them. This will help him to cut down on the need for bath salts. And if he observes any adverse effects on the skin, then the person should shun it and never try it.

How to Store the RO Waste Water?

Storing the RO waste water is an easy task. This is what it all requires you to do. Just drop the water ejecting pipe directly in a bucket to collect the water. However, you need to have a bucket of the appropriate size to store this water. Let us say the daily water consumption of your family is about 20 litres. The water wastage would be about 60 litres.

If your bucket is having a capacity of about 16 litres, then you would need to empty and re-fill it four times a day. The challenge would be checking on the bucket every time. If you fail to have an eye on it, the water may overflow, creating a mess in the kitchen. This may not be practically possible for many users.

Do not worry if you are one among them, because we have another solution for you.

Do you have a big tank outside your kitchen? If yes, extend the water pipe to this tank. This way, you can collect the water directly in the tank and store them for later use. Follow the below steps to know how:

  • Make use of a small submersible pump to draw water from this tank. We will tell you how to do. Just drop this pump into the tank and connect it to a power source.
  • Now, connect this pump to a water pipe to draw water from the tank. You do not require any bucket for this.
  • Moreover, there is no need to worry about the overflow. Since it is a big tank, you can stay stress-free.
  • Whether you are using a bucket, container, or tank, make sure it has a wide opening. Since you will have to clean it regularly, having a wide opening would make the job easier.


I hope this article sheds some light on the effective ways to use RO waste water. Now that you are aware of the various applications, you can save the waste water from actually getting wasted. Follow any of the methods, cited above to make the most of the rejected water.

Let us know in the comments section below if you tried these ways. Tell us your experiences by posting them in the comments. Write to us if you find this article insightful. Please feel free to share your inputs with us. If you have any points to add, do let us know them as well.

We would love to hear from you.

Stay healthy and stay safe!!!

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