How to Reduce Waste Water in an RO System | Guide
Written by: Gene Fitzgerald // Last Updated: Apr 17, 2023
This page may contain affiliate links. If you buy a product or service through such a link we earn a commission at no extra cost to you. Learn more.
Concern about waste water when investing in a reverse osmosis system is one of the most common.
Reverse osmosis needs a certain level of waste water to properly function and flush away contaminants, much like how water runs down the drain when you shower or wash your hands; it’s just part of the cleaning process.
However, if RO waste water is a big concern of yours, there are several things you can do to reduce the level of it, plus several creative ways you may be able to utilize your waste water for other things…
Contents
show
Key Takeaways
Here is how to reduce waste water in an RO system:
- Use an up-to-date reverse osmosis system – some older models waste much more water than the newer ones.
- Increase your home water pressure – feed water should have a minimum psi of 40.
- Install a pressure pump – to directly increase the water pressure flowing through your RO system.
- Install a permeate pump – this can reduce waste water by up to 85%.
- Recirculate the rejected water – you can send waste water through secondary filtration.
- Stick to the maintenance schedule – under-functioning system components can increase waste water.
- Reuse the waste water – collect the waste water to use for gardening, cleaning, etc.
How to Reduce Waste Water in an RO System
So, how to reduce waste water in an RO system?
Use an Up-to-Date Reverse Osmosis System
Reducing the waste water of your RO system starts at the purchase point. Some systems will simply be more efficient than others. Newer systems are often built with waste water in mind, and they tend to have better waste water ratios right off the bat, even without adding any extra pumps.
To check, when purchasing your system, make sure to ask the manufacturer about the waste water ratio.
Increase Home Water Pressure
Your home water pressure directly impacts the amount of water your reverse osmosis system wastes. A reverse osmosis system relies on pressure to push water through its membrane, and if the pressure is too low, then there won’t be enough force to do that fast enough, causing more water to be wasted.
Use a pressure gauge to check the pressure of your home water supply. Reverse osmosis requires a bare minimum pressure of 40 psi; if it is too low, you may need a booster pump.
Install a Pressure Pump
A pressure pump may be connected directly to your RO system to increase the pressure of the water flowing through it. This will ensure that the speed of the water passing through the RO membrane is enough to reduce the amount of waste water produced.
Install a Permeate Pump
A permeate pump is capable of reducing waste water by 75 to 85%. These pumps work by making the reverse osmosis system more efficient. The only issue is that not all models are designed to be able to use one, so check with the manufacturer if yours is designed with the ability to add a permeate pump. The pumps also do not run on electricity, making them even more efficient!
Recirculate Reject Water
Recirculating the waste water produced from your RO unit through a second RO membrane (or the same one) is possible. This will allow you to purify the water multiple times, considerably reducing waste production. The downside of this method is that it requires extra components which can be expensive and that reject water recirculation is usually only a thing with whole house reverse osmosis systems.
Stick to the Maintenance Schedule
If you notice changes in the level of waste water your RO system produces or in the output of your clean water, it may mean that filters or the RO membrane need replacing. Clogged membranes increase backpressure, which increases waste water. The same goes for worn-out pre-filters.
Reverse osmosis membranes need to be changed every two to five years on average, and pre-filters changed every 6 to 12 months, depending on the condition of your feed water.
Reuse the Waste Water
Collecting the waste water your RO system produces is possible by connecting your system’s drain pipe to a separate storage tank or bucket. You can then use that water for other purposes.
Why Does Reverse Osmosis Waste Water?
Reverse osmosis wastes water due to how it filters water. During reverse osmosis filtration, water flows through a semipermeable membrane with tiny pores that keeps contaminants on one side and only allows pure water molecules diffuse through to the other.
These pores are SO incredibly tiny that the system relies on water pressure to physically push the water through the pores. Unfortunately, the water pressure will not be high enough to push ALL of the water through the pores and leave only the contaminants. Plus, the system does have some backpressure that wouldn’t allow this anyway.
Besides, without the waste water, contaminants would stick to the reverse osmosis membrane and clog or damage it prematurely. So, it does help to think of wastewater as necessary for keeping your RO membrane clean.
How Much Water Gets Wasted?
Traditionally, the RO waste water ratio was 1:4, so one gallon of drinking water produced and 4 gallons of water wasted. Nowadays, it is possible to find systems with wastewater ratios as low as 4:1, meaning 4 gallons of drinking water produced for every 1 gallon wasted.
Smart Ways RO Waste Water Can Be Reused
Before using your waste water for other things, knowing what is in it is essential. Let’s say your system filters out lots of iron; then you won’t want to use the waste water, which now has concentrated iron, for washing white sheets as it may stain them. If your feed water is high in calcium and magnesium, then your waste water will have concentrated calcium and magnesium, which could affect the growth of certain plants.
If you have established that your waste water can be used for other things, here are some ideas!
Car Washing
Washing your car uses a lot of water, and more if you use a hose instead of a bucket. Using RO waste water to wash your car is perfectly safe and should not cause any harm to your vehicle.
Garden & Plants
Depending on the type of plant and the type of TDS in your waste water, it can be used for gardening. Often the waste water from reverse osmosis is hard water, and its contaminants can be harsh on certain sensitive plants, though.
Household Cleaning
Reverse osmosis water can usually be used safely to mop floors and clean utensils and silverware. Keeping some waste water in a bucket to use with detergents and disinfectants to clean is an easy way to utilize it.
Laundry Pre-Rinse
RO waste water can also be used to soak clothing or handwash items, providing the water is not discolored, and your more delicate items are not hard water sensitive.
Toilet Flushing
Waste water can be used to flush toilets rather than using the toilet flush button each time, and it can also be used to clean faucets and bathroom fixtures. Check to ensure that the TDS in your waste water won’t discolor porcelain, though.
Further Reading:
How to Store RO Waste Water?
A reverse osmosis drain line can be placed into a large tank, or you can use a bucket or container for smaller amounts that are regularly emptied.
Storing the water would require monitoring, depending on the level of waste water your system produces and how much you use it. For example, if you use 4 gallons of filtered water a day, and your waste water ratio is 4 gallons for every 1 gallon of pure water, then you will have 16 gallons of waste water daily, and you would need to check the storage container frequently to prevent overflow.
If you have any questions about how to reduce waste water from reverse osmosis please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.