Can RO Waste Water Be Used for Cooking?

Reverse osmosis happens to be one of the most efficient and convenient methods of treating water. It removes between 96-99.99% of contaminants found in the water.

RO water is healthier than tap or bottled water with any potentially harmful minerals, heavy metals, salts, and bacteria removed.

But it’s not without drawbacks.

One of the major downsides of reverse osmosis technology is waste water. The reject water is conventionally undrinkable.

Reverse osmosis waste water is rich in total dissolved solids and hence unsuitable for drinking, cooking, and bathing. It also contains organic matter in various quantities and inorganic salts that add to its unusable quality.

Why You Should Not Use RO Waste Water for Cooking

Reverse osmosis systems take tap water or well water and produce pure and waste water. The reject water is highly concentrated and has a majority of contaminants in it.

You don’t want to use water full of contaminants for cooking your meals, right?

Cooking with waste water can change the taste, smell, or color of the food you are preparing. For instance, minerals in the waste water can prevent proteins in your bread from absorbing all water when baking bread.

The minerals can also slow down the fermentation process.

Noodles, rice, and beans don’t have a lot of flavor on their own; if you use waste water (which could be smelly or with a foul taste), your food will be smelly or taste just like the waste water.

How Can You Use RO Waste Water?

Reverse osmosis waste water can be used in a number of ways to prevent the overall wastage of water in your home.

They include:

  • Watering the Garden
Can RO Waste Water Be Used for Cooking

You can use the waste water to keep your flower garden blooming. But always remember that this water is usually high in TDS and can reduce the fertility of the soil if used for a long time.

It’s therefore advisable to dilute the waste water with tap water before using it in the garden.

You also need to check the effect of the water on your plants. Try using it on different varieties and check its effect after a few days.

Doing so will give you a better understanding of the plants that respond well to the reject water.

  • Washing the Car
How Can You Use RO Waste Water

Washing your car can take several buckets of water. In fact, a car can consume anywhere between 14 and 75 liters of water. Quite a lot, right?

Using so much water on a car seems unreasonable. Imagine wasting all that water every day!

If using an RO system, store the waste water and reuse it to wash your car. If the water has a TDS level of more than 1500 PPM, you should dilute it with tap water before using it to wash your car.

  • Cleaning the Dishes

You can use the waste water to clean your utensils. You only need to store it in a bucket or container and place it near your kitchen sink. This way, you’ll be able to clean your dishes with ease.

  • Mopping the Floor

Using reverse osmosis waste water for mopping the floor saves tens of liters of potable water every day. Imagine persons with big houses and how much water they can save by recycling it.

If the TDS level of the water is too high, dilute the water with an equal quantity of tap water since you don’t want it to stain your tiles.

You can also use the RO water on alternate days to reduce the chances of stains or salt deposits on your floor.

  • Bathing Pets

You can also use the waste water for bathing your pet. But before using it, dilute with an equal amount of tap water since you don’t want it to irritate your pet’s skin.

Also, ensure that you dry the pet after bathing.

  • Flushing the Toilet

Although you can’t use waste water for bathing, you can, without a doubt, use it to flush your toilet. You, however, need to ensure that the water isn’t too concentrated to cause discoloration on your toilet seat.

  • Pre-Rinsing Laundry

Washing laundry wastes a lot of water which makes using RO waste water an excellent idea. You can use the water to pre-rinse your laundry.

Dissolved salts in the waste water can help to eliminate stubborn stains. However, it’s important to note that it might be unsuitable for delicate fabrics if the TDS level is too high.

If that’s the case, dilute the water.

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


Even if your RO system produces a lot of waste water, avoid the temptation of using it for cooking meals as much as possible. The waste water can interfere with the taste and smell of your food and, in worse situations, the color too!

The good news is that you don’t have to let the waste water go down the drain. You can use it to do household chores like mopping the floor and cleaning dishes.


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