Is RO Waste Water Safe to Drink? Find Out Here!
Written by: Alexandra Uta // Last Updated: Aug 18, 2023
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Reverse osmosis is a water treatment method that provides exceptional results.
But, unfortunately, it’s designed to produce waste water, which many people are uncomfortable with.
If you own a reverse osmosis system, you might be wondering if the waste water is safe to drink. This article has the answer.
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Key Takeaways
- RO waste water is not safe to drink. It contains all the contaminants filtered out by the reverse osmosis system in even higher concentrations.
Is RO Waste Water Safe to Drink?
So, is RO waste water safe to drink?
No, RO waste water is NOT safe to drink. It’s called waste water for a reason. RO waste water contains all the filtered-out contaminants.
The exact concentration of contaminants in waste water depends on how much water the RO system wastes. As a rule, the more water a system wastes, the less concentrated the waste water is.
For example, if system A produces 5 gallons of waste water for every filtered gallon and system B only produces 0.25 gallons of waste water per filtered gallon, system B’s waste water will be a lot more concentrated (5 times more than A).
Anyway, drinking RO waste water is like drinking a cocktail of contaminants. It’s unhealthy and completely unrecommended. Plus, it defeats purifying your water in the first place.
How Can You Use Reverse Osmosis Waste Water?
Although reverse osmosis waste water is unsafe for drinking, there are other ways to use it safely. They include:
1. Cleaning Chores
RO waste water can be used to handle cleaning chores at home. Since you don’t need purified water for tasks like mopping floors, scrubbing walls, cleaning windows, and washing utensils, RO waste water can be used with no issues. All you need to do is add a bit of soap to the waste water, and you’re ready to start cleaning!
2. Watering Plants
RO waste water can also be used to water plants. However, waste water containing very high levels of total dissolved solids (TDS) can be harmful to plants.
So, before watering your plants with waste water, check the TDS levels to be sure it’s okay. You can do this with a simple TDS meter. A TDS concentration of less than 700-800 ppm is usually ideal for watering plants. But if your TDS levels read 1000 ppm and above, you might want to keep the waste water away from your plants.
Another thing to consider is the type of plants you’re growing. If you’re growing highly sensitive plants, you’ll need to be more cautious. If you’re not sure how your plants may react to the waste water, test it on a few plants for about 15-20 days. If you notice any adverse effects like yellowing of leaves, it means your plants can’t handle the wastewater.
3. Washing Your Car
Washing a car could take anywhere from 4 gallons (if you use a bucket) to 20 gallons (if you use a hosepipe) of water. With RO waste water readily available, it’ll be a shame to waste gallons of tap water on your car. Using your waste water instead can help you save your tap water for more important things, like drinking and cooking.
4. Laundry Pre-Rinsing
Another way to put your reverse osmosis waste water to use is by using it for laundry pre-rinse.
Note: Waste water with a high TDS level can damage soft or delicate clothing. Test your water with a TDS meter before using it for laundry.
5. Flushing Toilets
Every time you flush, you send around 1-2 gallons of good water down the drain. There’s no need to do this when you have RO waste water available.
Note: Flushing your toilet with RO waste water can lead to discoloration on the surface. If you notice any discoloration, dilute the brine water with tap water before the next flush, or clean the toilet with any common toilet cleaner.
6. Cleaning Sewage Pipes
RO waste water is perfect for cleaning sewage pipes! And it doesn’t matter if your waste water has high TDS levels. Any level of TDS is fine.
Why Does Reverse Osmosis Waste Water and How Much?
Knowing how the reverse osmosis process works is the first step to understanding why it wastes so much water.
A reverse osmosis system uses a semipermeable membrane with tiny pores that block contaminants and stop them from mixing with purified water. The system sends the pure water to the storage tank, where it’s drawn up when needed, and it flushes the contaminants of the membrane and down the drain. The stream of flushed-out contaminants is referred to as waste water.
In other words, waste water helps an RO system work effectively by clearing out contaminants from the RO membrane; otherwise, the contaminants could pile up causing clogging.
The average RO system without a booster pump wastes 3-5 gallons of water for every gallon of filtered water.
Further Reading:
How to Improve the Waste Water Ratio of Your Reverse Osmosis Filter System
RO waste water is inevitable, but you can control how much water your filter system wastes. We’ve listed four tips to help you below!
Check Incoming Water Pressure
If your incoming water pressure is high, more water can pass through the membrane, and less water is taken down the drain as waste water. With low incoming water pressure, the reverse is the case.
If your water pressure is too low, increasing it can help you lower your waste water production.
You can increase pressure by:
- Including a booster pump in your RO setup – a booster pump can increase the incoming pressure and reduce waste water by 90+% in the process.
- Adding more pressure to your home’s plumbing
- Increasing the pressure valve’s water pressure (if your RO system has one)
Remember that your RO system should have pressure of 60 psi ideally. That’s the safe pressure level for most systems.
Recirculate Reject Water
Another way to improve waste water ratios is to recirculate and repurify the reject water.
Maintain Your RO System Properly
Maintaining your reverse osmosis system ensures that it doesn’t waste more water than it should. A badly maintained system is more likely to waste more water.
To keep your system in shape, replace your filters and membranes when due (most filters need to be replaced every 6-12 months and membranes need to be changed every 2-5 years).
Remember to keep an eye on other filter elements and replace them if you notice any damage.
Use a Modern Water Filter
A modern filter will often waste less water than an older model since they have a much better recovery rate.
Modern filters also have inbuilt booster pumps that reduce the amount of water the system wastes. For instance, the AquaTru RO system only wastes 20% of the feed water which is exceptional.
If you have any thoughts about the question, is RO waste water safe to drink, please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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