Your RO System Is Wasting Too Much Water? Here Is What to Do!
Written by: Alexandra Uta // Last Updated: May 3, 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.
In a sense, reverse osmosis systems are designed to waste water. That’s why, if you have an RO system at home, you should know how much water it wastes.
But what happens when it starts to waste more water than usual? Is there something you can do about it?
In this article, we’ll explain why your RO system might be wasting too much water and suggest ways to prevent it. We’ll also talk about why reverse osmosis systems waste water in the first place and how you can reuse your waste water to cut down waste.
Contents
show
Key Takeaways
Here’s what to do if your RO system is wasting too much water:
- Increase feed water pressure.
- Install a permeate pump.
- Replace the filter stages.
- Change a bad flow restrictor.
- Repressurize the storage tank if need be.
- Replace a broken ASO or check valve.
Your RO System Is Wasting Too Much Water? Here Is What to Do!
If your RO is wasting too much water, there are some simple fixes you can consider. You can:
Increase Feed Water Pressure!
Your feed water pressure affects how much waste water your RO system produces. If feed water pressure is too low, your system will produce more waste water.
Reverse osmosis systems work best with input pressure around 60 psi, so check yours to see if it makes the cut (you can do this with a simple pressure gauge).
If your feed water pressure isn’t high enough, you can increase it by:
- Using a booster pump. Booster pumps can reduce waste water production by about 90%. They operate with a motor and an electrical hookup.
- Increasing water pressure at the pressure valves (if your RO system has one).
- Adding more pressure to your home’s plumbing.
Install a Permeate Pump!
Permeate pumps can be used as an alternative to booster pumps. However, they work pretty differently. Permeate pumps use some of the RO’s reject water to power a piston which pushes the filtered water into the storage tank. This prevents the pressure in the tank from pushing against the RO membrane and improves the system’s effectiveness.
Permeate pumps also don’t require a power source or motor, so they’re energy efficient. The downside is that not all RO systems are designed to work with permeate pumps. So before purchasing one, ensure it’s compatible with your RO system.
Replace Filter Elements!
Proper maintenance will keep your RO system in good shape and prevent it from wasting more water than usual. The filter elements (like the pre-filters and RO membrane) need to be replaced on time because, over time, they clog and foul from the build-up of contaminants.
Most pre-filters need to be replaced every 6-12 months, while the RO membrane should be replaced every 2-5 years (the time frame for replacement varies across brands, so check your manufacturer’s instructions to know when you should replace your filters).
Replacing filters at the right time ensures that water flows freely through the system, improving overall efficiency.
Replace the Flow Restrictor!
Your flow restrictor might be another reason your RO system wastes too much water. A malfunctioning flow restrictor cannot push against the waste water stream to reduce the amount of water that goes down the drain. The effect of this is that your system wastes excess water.
You can’t repair a broken flow restrictor; The only solution is to replace it.
How to Fix an RO System That Constantly Drains
If your RO system constantly drains reject water, it may be one out of many problems, such as low pressure or a broken valve. Luckily there’s always a solution. Here are a few things you can try to get it fixed:
Repressurize RO Tank
Low storage tank pressure may be why your RO system is constantly draining. However, you can’t be sure your storage tank pressure is low until you’ve checked.
- To check the pressure in your RO tank, turn on your faucet and let it run.
- When the water flow stops, use a bicycle pump to slowly pump air into the storage tank. Any remaining water should now come out.
- Once the storage tank is empty, measure its pressure using a gauge.
An empty reverse osmosis water storage tank should read between 6 and 8 psi. If it reads lower than that, you’ll have to repressurize the tank. You can do that with the bicycle pump or even an air compressor.
Replace Broken ASO Valve
The automatic shut-off (ASO) valve usually prevents more water from entering your RO system after the storage tank is full. If it’s malfunctioning, it may be why your RO system keeps draining water.
To check if it’s broken, follow these steps:
- Allow the storage tank to fill – you’ll know it’s full when you lift it.
- Take 2-3 glasses of water from the RO faucet to reduce the pressure in the tank. Your system will then start processing water again to refill.
- Close the storage tank’s valve (to mimic a full tank).
- Wait for five minutes.
- See if the water stops flowing down the drain after you close the storage tank valve. You can do this by pulling the drain line out of the drain saddle. If the water has stopped, then both the ASO valve and the check valve are working fine. But if water is still running, one of the two is broken, So continue with the next step.
- Refill the tank one more time.
- Keep the storage tank valve open and shut off the feed water valve.
- Check to see if water is flowing down the drain. If it isn’t, the ASO valve is broken and needs replacement.
Replace Broken Check Valve
The check valve is what protects the RO membrane from backpressure. It allows RO reject water to flow down the drain line but prevents it from flowing back towards the membrane. If it stops functioning, the RO system will not stop running even when the tank is full, so water will keep flowing down the drain.
In order to check if your check valve is broken, follow the same steps for checking the ASO valve. However, in the last step, there’s a difference after you shut the feed water valve and leave the storage tank valve open. A broken check valve will cause water to drain from the storage tank even when no new water enters the system.
Low Feed Pressure
If your feed water pressure is too low, it could cause your reverse osmosis system to drain constantly. Increase pressure!
Clogged Membrane
A Clogged membrane will slow your RO system down, so it takes much longer to fill the storage tank. It will also cause the system to produce more waste water, possibly leading to constant draining.
Bad Flow Restrictor
A bad flow restrictor could allow lots of water to flow down the drain line and produce much noise. Replacing the faulty flow restrictor is the only remedy in this situation.
How Much Water Does Your RO System Waste?
Although many external factors contribute to the amount of water a reverse osmosis system wastes, one crucial factor remains the system’s design.
Usually, the manufacturer will state the amount of water a system is designed to waste in the manual. It could be written as “pure water to waste water ratio” (for example 1:1 or 1:4), or “recovery rate”, which is a percentage. A system with a waste water ratio of 1:4 has a 20% recovery rate, which means it only recovers 20% of the water sent into the system.
Most standard RO systems have a wastewater ratio of about 1:4 (4 parts waste water are produced for every one part of filtered water).In other words, it’s quite normal for RO to waste a lot of water and there might be nothing wrong with your setup.
Further Reading:
Why RO Wastes Water
An RO system wasting water happens due to the nature of the filtration process. RO systems pressurize water causing it to diffuse through their reverse osmosis membrane in order to purify the water.
But not all the water can make it to the other side. Some is left together with all the contaminants. These contaminants get flushed out in a waste water stream which prevents them from building up on the membrane surface.
Hence wastewater is produced as a consequence of the membrane’s working principle. This principle is important because if contaminants are allowed to build up, they would damage the membrane and foul it prematurely, rendering it ineffective.
How to Reuse RO Waste Water
RO wastewater doesn’t have to go to waste. There are so many ways to recycle and reuse it, including:
- Household cleaning: RO waste water can be great for household cleaning. You can use it to clean floors, bathrooms, or outside furniture.
- Laundry pre-rinse: Although RO waste water might not be a good idea for main laundry water because of potentially high TDS levels, you can use it to pre-rinse your laundry.
- Gardening: You don’t need pure water to water your plants. So gardening is an excellent way to recycle RO waste water. Just make sure there isn’t too much sodium.
- Washing your car: RO waste water is pretty safe for washing your car. You can still get that shiny look as long as the water is not too packed with suspended solids.
If you have any questions about RO wasting too much water please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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.