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Reverse Osmosis Waste Water for Watering Plants: Pros & Cons

Reverse Osmosis Waste Water for Watering Plants: Pros & Cons

Reverse osmosis water is essentially free from minerals or chemicals, making it a desirable method of water purification. However, this process also results in a notable amount of wastewater.

This water is usually high in minerals and chemicals from the filtering process; however, it can still be useful for other applications. 

Is RO waste water safe for plants? RO wastewater is safe for plants but can be harsh if in an extreme concentration. Always check the TDS to ensure it is below 800 ppm so no harm will come to your plants. In some cases, the RO wastewater is high in fluoride, chlorine, and other additives that can negatively affect your plants.

While we prefer to drink RO water, you can use RO wastewater to water your plants and do other household chores.

Read on to understand what RO wastewater is, why it can be a good (and bad) choice to water your plants with, and also how you can use it to reduce water waste and still be productive in your home!

RO Wastewater for Plants – What To Know

Using RO wastewater is a great way to reduce the amount of water that goes down the drain. While it can be high in TDS (Total Dissolved Solids), urban water is usually lower in TDS because it is treated. 

What Is RO Waste Water?

RO wastewater is a byproduct of Reverse Osmosis filtration. Common tap water is usually treated with countless chemicals to kill bacteria and viruses and also may have been contaminated by old piping or poor water treatment. 

When the RO water filtration takes in water, it uses pressure to filter it through fine membrane filters, expelling water with a high concentration of these impurities.

Unfortunately, it is common for ¾ of the water that runs through an RO filtration system to be wasted while only ¼ comes out as filtered usable water. 

Impurities and Contaminants in Reverse Osmosis Waste Water

Common tap water is treated with chlorine and fluoride by water companies to remove viruses and bacteria. Unfortunately, these are used in high quantities and don’t always kill what they are meant to.

Other contaminants like heavy metals can make their way into the water from old piping while impurities like sodium and other minerals can be found in high concentrations not safe for humans.

Is RO Waste Water Good for Plants?

Some plants will find RO wastewater just as hydrating as water from your tap, but some will be picky when it comes to water and not handle wastewater well.

It can be good for some plants because it delivers a high amount of trace minerals that can be great, and the plant is able to filter out any chemicals it doesn’t prefer. 

Benefits of Using RO Waste Water for Plants

While RO wastewater is high in impurities and chemicals, it is also high in minerals that plants need to survive.

It is a good way to save water and reduce your water consumption since it is just a byproduct of the water you are already filtering. 

Considerations Before Using RO Waste Water for Plants

It is always important to check the TDS (this meter is accurate and very affordable) that your wastewater has before using it on your plants.

Always checking the TDS level in your wastewater will help determine if it is viable to use for watering.

Plants can tolerate TDS concentrations of less than 700-800 ppm but may show signs of stress in this range or with a ppm higher than that. 

How To Use RO Waste Water for Plants

It is easy to use wastewater for your plants! Simply collect your wastewater, and then water your plants as you would regularly water them.

Follow the list of steps below to ensure you use it without adversely affecting your plants’ health. 

If you notice that the leaves begin to yellow or signs of their health declining, stop using wastewater and switch back to regular water. 

  1. Check the TDS level of your RO wastewater to ensure it is in a usable range and won’t harm your plants. 
  2. Retrieve wastewater from the RO filtration system by locating the wastewater line and filling your watering can or pitcher. 
  3. Water your plants by only watering the soil. Avoid putting water directly on the leaves of your plant as the chemicals may burn the leaves if highly concentrated. 
  4. Monitor your plants to ensure the use of wastewater doesn’t affect their health. Signs of poor water quality will include yellowing leaves or a lack of vigor.

How To Collect RO Waste Water

Check your RO water filtration system to find out from where the wastewater is expelled. Many times, there is a separate tube that will deposit wastewater into a drain.

Once you locate the drain line, place a bucket or pitcher under it, and open the valve to fill your container with wastewater.

You can also use a large tank to continuously collect wastewater to always have it on hand in a greater supply. 

RO Waste Water Uses

The best uses for RO wastewater are ones that don’t include things that may be affected by high levels of impurities.

Using RO waste water for regular chores like washing your car or toilets or mopping is a great way to utilize this water. If the TDS levels are acceptable, watering your plants is also a great way to utilize the water. 

Related Questions:

Can RO Waste Water Be Used for Cooking?

It is not recommended to cook with RO wastewater since it has high levels of sodium and chemicals that may cause health issues if consumed.

It is better to use filtered RO water for cooking and leave the wastewater for tasks that don’t involve human consumption. 

Can RO Waste Water Be Used for Bathing?

RO wastewater is most likely too harsh to bathe with since it has such concentrated impurities. The high levels of contaminants will affect your skin and hair health if you use it to bathe. 


RO water is great for drinking and creating a good baseline for use in aquariums and other TDS-sensitive applications.

However, it is never fun to waste water, and RO filtration creates a lot of wastewater!

Use it for alternative ways to water your plants or for basic chores around the house. You’ll save water and still get everything done on your to-do list!