How to Collect and Store RO Waste Water | Guide

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There are a few ways you can collect and store your reverse osmosis waste water in order to be reused or repurposed, and some methods are definitely easier than others!

Before we delve into it, though, an important thing to note is to be aware of what contaminants may be lurking in your waste water. If certain pollutants are in concentrated amounts, they may not be suitable for specific purposes (for example, too much sodium won’t be ideal for watering plants).

Now that that’s out of the way, let’s look at how you can collect and store your RO waste water!

Key Takeaways

  • Using a reject water tank is often the simplest way to collect and store your reverse osmosis water. Run your RO waste water line directly into it rather than connecting it to the drain saddle under your sink.

Collection: How to Store RO Waste Water

There are several ways you could collect and store your reverse osmosis waste water for alternate uses (depending on what’s in it, of course!) But the easiest way is to use a reject water tank…

Use a Reject Water Tank

The simplest way to collect your RO waste water is to reroute the waste water line from the drain pipe to a reject water tank. Ideally, this tank should be large enough that you aren’t running to empty it five times a day, but any tank or bucket that won’t overflow would do.

Remember that your RO system may produce a lot of waste water, depending on the model you have and various other factors. For under sink units, it could be 3 to 5 gallons for every gallon of water you use. If you only have a gallon bucket, then it will end up full way too quickly to be convenient.

Connect Drain Tube to Washer

If you have some DIY experience or someone willing to help, it is possible to run the waste water drain line directly to your washer and utilize the RO waste water for washing clothing. This is only recommended if you do not have any discoloration in the waste water that could stain your clothing, though.

Washing machine

Connect Drain Tube to Toilet Cistern

It is possible to connect your RO waste water drain tube to your toilet cistern so that you are using waste water when you flush your toilet rather than your regular household water. This would likely require the assistance of a plumber to run the lines to the bathroom.

Create a Waste Water Outlet for Your Garden

You could also run your RO waste water line directly outside to your garden or planter boxes, provided that the plants you have there are okay with the level and type of dissolved solids in the water. You would also need to make sure the plants were not the kind to easily succumb to overwatering.

Simply Allow the Waste water to Flow to the Sewerage

Eventually, the RO waste water will end up at a water treatment plant, where it will be filtered and recycled.

Other Ways to Reuse RO Waste Water

You can use your RO waste water around the home in several different ways.

  1. As a cleaning agent: Tasks such as mopping floors, cleaning windows, and washing utensils can all be performed with RO waste water as long as it’s not overly dirty.
  2. Water your indoor plants: Provided your RO waste water is not too high in sodium and similar impurities that can be harmful to plants, you can use the waste water to water your indoor and outdoor plants.
  3. Clean your car: RO waste water can be used to wash your car rather than tap water from the hose. The contaminants in the waste water should do no damage to the outside of your vehicle.
  4. Soak your laundry: You can add pre-rinse ingredients to RO waste water for your laundry to soak in before putting it through the wash cycle.
  5. Flush your toilets: If you don’t want to run the waste water line to your toilet cistern, you can still flush your toilets with RO water simply by pouring it into the toilet bowl.

How Much Water Does a Reverse Osmosis System Waste, and Why?

The amount of water a reverse osmosis filter system will likely waste depends on numerous factors. The main one is the model you have, as some models are simply more efficient than others.

It is possible for your RO system to waste 5 gallons of water for every 1 gallon filtered, all the way to only a quarter gallon of water for every gallon filtered. Check with the manufacturer before purchasing to see what the estimated waste water ratio of your machine might be. This may be described as the system’s ‘recovery rate’, which means the percentage of purified water produced.

So, why do RO systems waste water at all? Simply put, it needs to in order to function effectively. If it did not, filtration would be incredibly slow and contaminants would build up on the reverse osmosis membrane and clog it. RO membranes are flushed with water as they filter to dislodge any stuck contaminants and ensure they are sent down the waste water drain.

How to Increase the Recovery Rate of Your RO System

There are easy ways to reduce the waste water output of your reverse osmosis system and thus increase its recovery rate:

Under Sink Reverse Osmosis System

  • Water pressure is the first thing to look at. The higher the water pressure moving through the reverse osmosis system, the less waste water will be produced. Check the water pressure of your home. A reverse osmosis system needs a minimum of 40 psi to function properly – 60 psi is much better and produces far less waste – and if your home’s output does not reach this, you may need to install a booster pump.
  • The next thing you can do is install a permeate pump. These can reduce waste water by up to 80%, but they don’t work with every RO model. By the way, permeate pumps are different from regular booster or pressure pumps as they don’t require any electricity. How is this even possible? Permeate pumps use the waste water pressure to counter backpressure from the RO storage tank which increases membrane efficiency.
  • A dirty, clogged RO membrane will also cause more waste water, as that reduces the pressure of the water too. The same goes for old pre-filters. Ensuring system maintenance is performed at the scheduled time is vital to prevent this.
  • In theory, you could recirculate all or some of the waste water and have it go through one more round of purification. This is usually only a thing with whole house reverse osmosis systems, though.

If you have any questions about RO waste water collection 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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