RO water purifiers have become increasingly common these days. If you have owned an RO purifier, then you would know that it comes with a waste-water reject outlet. Many households store this water and use it for household chores. In this article, we will discuss best ways to use RO reject water.
Why You Should Re-Use RO Reject Water?
RO water purifier wastes 65 – 80% water. It means that, for producing 1 litre of pure water, RO water purifier will waste 4 litres of water. This RO reject water is full of inorganic salts and other impurities. This makes the water unfit for consumption because such water can cause damage to human body. This is a big drawback of RO purification system. Therefore, it our responsibility to re-use this water whenever we can.
10 Best Ways to Re-Use RO Reject Water
RO reject water is high in TDS levels, which means it is high in inorganic salt content. Due to this, it can damage some metals, floors and other surface if used directly. Therefore, as a general recommendation, diluting this water by adding at least equal amount of regular water should always be considered.
1. Car Washing
Using waste water for car wash is one of the best ways to reuse RO waste water. This is because single car wash with bucket can use anywhere between 15 and 30 litres of treated water when bucket is used. Its higher when a hose-pipe is used. All you need to do it collect waste water in a bucket and you can clean your car with this water.
Since RO water’s TDS can be around 2000 ppm, which is not good for your vehicle, you can dilute this water in 1:1 ratio with regular water to wash your car. If you are not able to dilute, then you should wash it with waste-water but use clean water for final rinse.
Water Saved = 15 – 30 litres
2. Washing Utensils
Since RO water purifiers are mostly placed in kitchen, washing utensils can be a smart and easy way to reuse expelled water. In fact, this high TDS reject water can be quite good for washing utensils. It is sometimes recommended to do the final rinse with clean water as well.
3. Mopping Floor
Mopping floors take a lot of water. If you can use RO reject water for this purpose, then you can save at least 30 litres of water. However, this water can leave visible salt particles on floor if used directly. Therefore it is always recommended to dilute this water with regular water in equal parts before using it. Also, you may want avoid using it on a daily basis if you want to be extra cautious.
4. Watering Plants
If you have a garden in your home or if you are planning to grow plants in your balcony or terrace, then you should consider using reject RO water to grow for watering these plants.
You can store the rejected water in a bucket or plant watering can for the plants.
Since this expelled water contains high level of TDS, you should use this method with care. High TDS and high level of sodium is not good for plants and because you can’t check the levels yourself, it’s always recommended to do a trial on each type of plant for few days to see if it not effecting them adversely. This is necessary because each type of plant will reacts differently to different type of water. There are many types of plants that grow well in such saline water.
5. Washing Clothes
High TDS of RO water can harm delicate clothes, therefore you should use this water for washing clothes that are not very delicate such as carpets, blankets, curtains. If you are not sure if your cloth fabric is right or not, then you can pre-rinse clothes with this water. In short, you can pre-rinse all types of clothes.
Also, you can dilute this water by adding more than 50% of fresh water in it to avoid damage to regular clothes.
6. Cleaning and Flushing Toilets
One single flush can take 3 to 6 litres of water. It means that a family of four can use around 36 litres of water in a single day, only for flushing. In fact, because so much water is wasted in this process that some developed countries have started using sea water for this purpose.
To use it for flushing, you can this water in a bucket or a big tank and connect the pipe from this tank to the toilet flush system.
It’s best practice to check your toilet seats for any discoloration on the surface after a few days. Many users use this method periodically to avoid any damage.
7. Bathing Pets
You can use RO waste-water for bathing your pets as their skin and hair are tougher than humans. However, few pets are sensitive to hard water, therefore you should monitor your pet for few days to continue bathing them with this water.
8. Add Back to Water Tank
10th grade science teaches us ‘dilution is the best method of purification’. One of the best ways to recycle RO waste water is to put this water into the water tank. When RO waste water mixes with tank water, it gets diluted and the overall TDS of the tank water increases only marginally. If you want to put water directly into water tank is on top of your house then you can buy a booster pump for pushing water into the overhead tank else you can add it to the tank below the ground as per your convenience and preference.
9. Boiling Eggs
Using waste-water for boiling eggs is an innovative way to reuse it. This is not harmful because the edible portion of the egg will be covered with hard curst and will not come in direct contact of waste-water.
10. Air Coolers
You can use this water to fill your air coolers during summer season. This is a perfectly safe and easy way to use this water. In fact, you can use this water for heating any food item with hard cover on top. If you want to know a good way to reuse waste-water in winter, then you should read our next tip.
11. Hot Water Bottle
Many Indian households use hot water bottle to keep themselves warm during winter season. You can use this waste-water for filling up these bottles without any guilt.
How to Reduce Waste Water in RO Purifier?
If you want to reduce water wastage from RO purifier, then you first thing that you can do is to install an additional water tank that collects the expelled water. This is give you a convenient storage mechanism and you can use this water in different ways discussed in this article. This is not as difficult as it sounds and households are using this method to reuse waste water.
Some water purifier brands have come up with their water saving technologies. For example, Kent’s ‘Zero Water Wastage’ technology helps reduce water wastage to some extent. It is a technique in which waste water is pumped back onto the overhead tank so that it gets mixed and diluted with the tank water. This technique reduces the water wastage and only 50% of the water gets rejected. This means that it saves at least twice more water as compared to regular water purifiers.
Again, many water purifiers come with auto shut-off feature that shuts off the water purifier once the tank is full. This reduces unnecessary wastage of water.
Another way to reduce wastage is by feeding the reject-water into another RO system. This will save 20 – 30% water because second RO system will purify it and give 20 – 30 litres of water for every 100 litres of discarded water. But this method also comes with a drawback. High TDS level of reject water can cause scaling in the second RO system, therefore pre-treatment is necessary for second RO system. Many large organizations are using this method to reuse reject water by this technique commercialised as Tubular Membrane Filter (TMF).
Can I Use RO Waste Water for Bathing?
RO waste water is hard water and may irritate your skin and damage your hair. It is usually not recommended to use this water for bathing. If you still want to use it for bathing, then you should keep things in mind.
- Bathing accessories such as shower heads can experience staining from this hard water.
- Very high TDS water can irritate the skin and may lead to hair fall. So, if you want to use it, you can bath for few days and see if it suits your skin. Alternatively, you can dilute this water before bathing as well.
- Hard water may not produce enough foam. Again, best way is to try once and see if you are comfortable with this level of foam.
- Some research suggest health benefits of additional salts and minerals present in this water.
In our experience, dilution is the best way to bath with RO reject water. Try to dilute it by adding at least equal amount of regular water.
Frequently Asked Questions (FAQs)
What is the TDS of RO waste water?
TDS of RO waste water depends on input TDS and your water purifier. Still, a TDS of 1800 or above is quite usual for waste water.
Is there an RO water purifier with zero water wastage?
RO purification is a water intensive process. RO purification without water wastage is not possible with current technology. However, there are purifiers such as Kent Grand Plus that come with wastage reduction technology.
Can RO waste water harm garden plants?
Different plant types react differently to hard water. It’s recommended to monitor them for few days before regularly watering them with this water.
Can I bath with RO waste water?
It is usually not recommended to use this water directly for bathing.
How much water does an RO purifier waste?
RO purification wastes 65 – 80% water.