Can Wastewater from RO be Used? Four Tips for Sustainable Use Vyair LTD.




Reverse Osmosis (RO) is a highly effective method of removing contaminants from tap water, producing TDS water for home brewing, making beverages among other uses. Among the contaminants removed are organic and inorganic salts, amongst metallic and non-metallic compounds.

In the process of filtration, the RO recovery rate can be up to 75% on most modern RO units. Manufacturers accept this is an issue and are working towards no waste or wastewater models. In the meantime, there are ways you can use the rejected water around the house, in the bathroom, and outside.


Washing Cars.

Using RO wastewater to wash your car is a great way to make the best out of it. An average carwash with a bucket can consume 15 litres or 6 buckets of water. If you wash your car frequently, that’s a huge amount of water being wasted. This is especially true if using a hose – studies suggest that a pipe uses up to 75 litres to wash one car. It’s all the more wasteful when you consider only half of the water coming from the pipe is used to wash the car, and the rest runs off totally wasted. Going to the car wash is no more sustainable. A wash can use up to 120 gallons of water per vehicle, which can add up to millions of gallons a year per car wash.

Save the water in your taps and use your RO wastewater when cleaning your car. It’s a good use of the reject water and has great results!


Watering Your Plants.

You can use your RO reject water whilst gardening, although it is recommended that you do some research on your local water supply firsts. There are high amounts of nutrients and minerals in the water that your plants will love, and they can grow fast and strong if you do use RO wastewater. However, this is only advisable in areas where levels of TDS (total dissolved solids) in the water supply are low. This technique is recommended especially in urban areas, where you are more likely to find low TDS municipal water.

Store the wastewater in a bucket or a can ready for use on your plants, just make sure you do some tests first. Along with testing TDS levels, it's worth measuring the level of sodium in your tap water too, high sodium levels can have adverse effects. We would recommend mixing the RO wastewater with some tap water for the best results, as the undiluted water could act as a poison for your plants.


Use it Around the House.

There’s no getting away from doing the cleaning every day. Mopping the floor, washing utensils, and doing your laundry all require excess water, and what better to use than RO wastewater that is bound for disposal. A tap runs at 2 gallons per minute and so saving your runoff water is an efficient way of doing household task whilst saving water. You can mop your floors with RO water without worrying about treating or mixing it with fresh water. Prewash your dishes with reject water, however, we recommend rinsing with fresh tap water to prevent salt build-up and keep your dishes from ruining.

RO wastewater can also be used with your laundry, as the salts rendered in the can help to remove stains. Some fabrics could have an adverse reaction to the RO water, so we would recommend mixing 1:2 with fresh water.


Use it in Your Bathroom.

Even though bathing in rejected water is not advisable, there’s still a use for the rejected RO water in your bathrooms. Flushing the toilet takes up to 7 litres each time, and daily up to 40 litres of water. Using RO rejected water to flush your toilet is simple, just throw the water down the cistern. Manual flushing is becoming more commonplace worldwide as a way to save water, and this technique kills two birds with one stone!

As well as manually flushing, you can use your RO reject water to clean your bathroom. The saline nature of the water is good to clean pipes, and when diluted with equal measures of freshwater it can be used to clean the porcelain and the surfaces. Just make sure to test the water and monitor results. Discolouration and salt deposits can occur, so this method for cleaning is only recommended for periodical deep cleans.


Reverse osmosis systems continue to be an effective means of filtration. As technology improves, the efficiency of the systems will increase, and the amount of wastewater will naturally decrease. These techniques will see that the wastewater is used until then. Our RO units are as efficient as you can get on the market, and highly effective, running from 50 to 900 Gallons per day. Take a look at our bestselling compact 4-stage unit below or check out our website or Amazon/eBay listings for the full range.  If you need advice about what to do with your reject RO water or anything else, our team will be happy to help!



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