6 Simple Ways for How to Re-Use RO Waste Water

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Are you tired of watching gallons of water go down the drain every time you use your reverse osmosis system? We get it.

Many people wonder what to do with their reverse osmosis waste water.

Thankfully, there are many ways to reuse RO brine water so that it doesn’t go to waste. This article shares some simple, safe, and practical ways.

Key Takeaways

Here are some practical things for what to do with reverse osmosis waste water:

  • Clean your home
  • Water your garden
  • Wash your car
  • Pre-rinse your laundry
  • Flush and clean toilets
  • Clean sewage pipes

What to Do with Reverse Osmosis Waste Water?

So, what to do with RO waste water?

Instead of letting your reverse osmosis reject water go to waste, collect it carefully and store it for later use. We’ll discuss some safe ways to reuse reverse osmosis waste water below.

6 RO Waste Water Uses

RO waste water is unsuitable for drinking, bathing, or cooking, but there are other ways to use it. Let’s see some of them!

1. Cleaning Your Home

Reverse osmosis waste water can be used for general cleaning around the home. For example, you can use it for mopping floors, cleaning windows, and washing utensils. Add mild liquid soap to the waste water, and you’re good to go!

Cleaning Sponge with Foam Heart

2. Gardening

RO waste water can also be used to water plants, but there are things to consider before gardening with RO waste water.

For instance, does your RO waste water contain very high levels (over 1000 ppm) of total dissolved solids (TDS)? Do you grow plants that are highly sensitive to common water contaminants like sodium and chlorine?

If you answer yes to both questions, using RO waste water for gardening will not be a good idea. The contaminants in the waste water could damage your plants, causing leaf yellowing and other side effects.

Tip: If you’re unsure about how your plants will respond to RO waste water, you can perform a small experiment: Water a few plants for about 15 days and observe them for any negative changes.

3. Washing the Car

Washing your car with RO waste water makes a lot more sense than using unfiltered or even precious purified water.

Car washing usually takes a lot of water, so you can save your (purified) water for other important things like cooking and drinking.

4. Laundry Pre-Rinse

Another excellent idea is to do your laundry pre-rinse with your RO waste water. Waste water contains salts that help remove stubborn stains and dirt in clothes.

Using RO waste water for laundry pre-rinse is safe unless you’re washing delicate clothing and the water contains very high TDS levels. Waste water with high TDS levels can damage soft clothes. To stay safe, test your water TDS level to know where your waste water stands, and remove fine or delicate fabrics before pre-rinsing with waste water.

5. Flushing and Cleaning Toilets

A ridiculous amount of water goes to flushing and cleaning toilets daily. There’s no need to flush and clean toilets with freshwater, though, when you can reuse the waste water from your RO system.

Note: Your toilet’s surface may get discolored if the waste water has very high TDS levels. If you notice any discoloration after flushing or cleaning, mix the waste water with purified water (to dilute it) before using it for the next flush.

6. Sewage Pipe Cleaning

The water for cleaning sewage pipes does not have to be contaminant-free, so why not? Even if your RO waste water contains a lot of TDS, you can clean your sewage pipes with it without diluting.

How to Store Reverse Osmosis Waste Water?

Before reusing your RO waste water, you must collect and store it. Here are two ways to store reverse osmosis waste water:

  1. Drop your RO drain line in a bucket or container: This is a simple method, but you’ll have to keep an eye on the bucket so it doesn’t overflow (replace it once it’s full). Regularly replacing buckets may not be convenient, considering the large amounts of waste water an RO system generates.
  2. Connect your RO drain line to a large tank outdoors: You can install a submersible pump in the tank and create a pipe outlet to receive waste water. This method is more convenient in the long run.

Why Should You Reuse RO Waste Water?

Many reverse osmosis systems waste a lot of water, far more than they purify.

By reusing the waste water, you can reduce the amount of water that goes directly into your local sewer system, which means you reduce your water and utility bills. Plus, it’s more environmentally-friendly.

Can I Use Reverse Osmosis Waste Water Without Danger?

You can use your RO waste water without any issues, depending on what you’re using it for and how contaminated the waste water is.

Things to Keep in Mind

Remember that if your feed water contains many contaminants, the RO waste water will have even higher levels of each pollutant. And the better an RO system’s recovery rate is – recovery rate can also be described as the pure-to-wastewater ratio – the higher the salt concentrations in the wastewater will be.

For example, the AquaTru RO system wastes as little as 0.25 gallons per gallon of purified water. As such, the TDS level in the reject water will be about five times higher than in the feed water.

So if you have high levels of, let’s say, sodium in your feed water, the waste water will have higher levels of sodium and be unsafe for gardening (sodium overload can wreck plants). If you have lots of dirt and sediments in your feed water, the waste water will be extremely contaminated and unsuitable for laundry pre-rinse.

Basically, whether you can use your RO waste water without danger depends on the level of contaminants in your water and your use case.

Why Does Reverse Osmosis Waste Water and How Much?

Understanding how reverse osmosis works will help you understand why it wastes water so much.

Reverse osmosis uses a semi-permeable membrane to reject contaminants in water. The system releases clean, contaminant-free water at one end, and there will be a second water stream which flushes out all the impurities. This second stream leaves the RO membrane housing via the drain line releasing “reverse osmosis waste water”.

blue reverse osmosis membrane

A large amount of waste water helps the RO system to purify water effectively; it’s just how it works. A standard under sink RO system wastes four to five gallons of water per gallon of purified water.

How to Improve the Waste Water Ratio of Your System

Having some waste water from a reverse osmosis system is inevitable, but you can reduce the amount significantly. Here are four tips to help!

1. Increase Feed Water Pressure

When feed water pressure is high, the force pushing the water through the RO membrane is also high. That means more water passes through the membrane, and less water is discarded as RO waste water. So if you want your system to produce less waste water, increase the water pressure in the system.

You can do so by

  • adding a booster pump to your RO system. A pump can significantly reduce waste water by up to 90% and more.
  • increasing water pressure at the pressure valve, if the system has one.
  • adding more pressure to your home’s plumbing.

Remember that the ideal water pressure for reverse osmosis systems is 60 psi. The absolute minimum is 40 psi. So make sure you keep your water pressure within this range.

2. Recirculate Reject Water and Purify Again

You can repurify your reject water to minimize the quantity of water that ends up as wasted.

However, this is usually only a thing with some whole house reverse osmosis systems.

3. Keep Your Reverse Osmosis System in Tip-Top Shape

A healthy reverse osmosis system will produce less waste water than an old, clogged one. You should keep your RO system in good condition by replacing the filters and membranes when due (every 6-12 months and 2-5 years, respectively). Also, examine the filter elements and replace any damaged parts immediately. That way, you can ensure your RO system does not produce more waste water than it should.

4. Use an Up-to-Date Filter System

Modern filter systems often have a higher water recovery rate. They come with inbuilt booster or permeate pumps that help to reduce the amount of water that goes down the drain. For example, the AquaTru RO system wastes only 20% of the feed water. Using such an up-to-date model is the most effective way to minimize waste water.

If you have any questions about what to do with RO waste water please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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