If you want to invest in reverse osmosis (RO) water filter for your home, you will probably like everything about this system, except from the fact that water is wasted through this filtration system. Unfortunately, there is no direct way to avoid wasting water in reverse osmosis. Although many RO systems are much more efficient than conventional systems, this filtration method does not entirely eliminate water wastage.
So at this point, various questions arise. Some of them are:
- Why does a reverse osmosis system waste water?
- How much water does a reverse osmosis process waste?
- How to minimize waste water through reverse osmosis?
You need to read this guide to get your answers in detail.
Why Does a Reverse Osmosis System Waste Water?
To understand why a reverse osmosis filter wastes water, you need to understand how does a RO system actually work?
A typical non-reverse osmosis water filtration system contains multiple filter cartridges. Water flows through these cartridges, and impurities are trapped in the pores of the filters. RO systems work in a complex way. Many reverse osmosis systems use multiple filter cartridges, but the star is a semi-permeable membrane.
This membrane has tiny pores, much smaller than standard cartridge filters, typically around 0.0005 microns. Water is forced through this semi-permeable membrane. The composition of small water particles allows them to pass through the membrane, while impurities in water are too large and are rejected by the membrane.
Without wasting water, these contaminants accumulate in the RO chamber as water flows through the system. With nowhere to go, contaminants keep hitting the membrane. Over time, an excessive number of contaminants trapped within the chamber will damage the RO membrane.
Water is used to wash these membranes by the RO system. Where does reverse osmosis waste water fit in the equation? Well, something has to wash all these contaminants away. Water is beneficial for cleaning these membranes from the trapped contaminants until you change your damaged filter membrane.
How Much Water Does a Reverse Osmosis Process Waste?
Reverse osmosis wastes 4 gallons of water for every gallon of pure water produced. The amount of water discharged is described in more detail below. The waste of RO water is not that big. After installing a reverse osmosis system, your water bill may be a little higher than normal, but water wastage is minimal if you use this system for potable water only. Suppose you are a family of four, each drinking 0.5 gallons of water a day (recommended), a total of 2 gallons of pure water is your need. In other words, a traditional RO system wastes 8 gallons of drinking water per day to provide 2 gallons of purified drinking water.
Water Waste Ratio for Reverse Osmosis
For every gallon of purified water a reverse osmosis system produces, you probably use about 4 gallons of water. The conventional water wastage ratio for reverse osmosis systems is approximately 1:4. For every gallon of water produced, 4 gallons are wasted.
How to Minimize Waste Water through Reverse Osmosis?
Although you cannot directly eliminate the waste water by reverse osmosis, here are a few useful tips to minimize it.
1. Waste water Recycling
There are different ways to “recycle” waste water. Some filters circulate the waste water and use it continuously in the filtration process. However, this is not always the best option as it can increase filter wear and tear.
Another way to recycle waste water is to pipe it through a hot water tap or other fixture that doesn’t require pure water. If you choose this second option, be aware that reverse osmosis waste water contains high concentrations of impurities. Shortly, it is helpful for limited purposes.
2. Use Modern Systems
First, avoid inefficient reverse osmosis systems and look for systems that don’t waste water unnecessarily. Modern reverse osmosis systems must have much more efficient water waste rates. Some systems achieve this by simply reducing the amount of water exiting the RO chamber during filtration. In contrast, others are even more efficient, re-circulating the waste water through the system twice to minimize the amount of water reaching the drain.
3. Check Water Pressure
Lower water pressure can result in higher levels of reverse osmosis drainage. Check your pressure-reducing valve if you own a well below the ideal 35-40 PSI range. If all is well, contact your local water authority to see if your facility has pressure issues. You can use a booster pump to deal with low water pressure issues. You can adjust water pressure through this pump according to your needs.
4. Regular Maintenance of Reverse Osmosis Filters
A reverse osmosis filter is not a “set and forgets” product. Also, high-level maintenance is not required; check from time to time. First, familiarize yourself with the system. Most efficient reverse osmosis filters use up to 5 stages. Each stage has different filters designed to trap different types of particles.
Reverse osmosis membranes can last up to two years, but most other filters (including sediment, carbon, and abrasive) should be replaced yearly. When replacing these filters, you should thoroughly clean the entire system. Remove all filters (leaving the housings in place) and pour 1 cup of hydrogen peroxide into the filters. Then pass through at least 2 cycles. Taking good care of your reverse osmosis filter will not only reduce water waste, but it will also last longer. It’s not uncommon for a well-maintained filter to last up to 15 years.
Reverse osmosis filters are designed to purify the contaminated water. These filters use specific membranes that trap the contaminants. On average, a RO system uses 8 gallons of water to give 2 gallons of purified water. You can use this wasted water for many other activities like house cleaning, gardening, planting, etc.
Frequently Asked Questions
1. Why does a reverse osmosis filter produce waste water?
Water itself is not “waste.” Rather, it generates the high pressure required for the reverse osmosis process. It’s not completely accurate to call the reverse osmosis process a “water waste,” just as you wouldn’t call a bath a “water waste.”
2. Does countertop reverse osmosis waste water?
Yes, even the best reverse osmosis systems still waste water. In this case, the waste water is collected in the waste water compartment. The system warns you when this compartment is full. The compartment must be removed and emptied of water before continuing with the RO process. Countertop RO systems do not waste more or less water than under-counter units.
3. Can RO waste water be used for cooking?
Due to the higher than average concentration of contaminants in reverse osmosis waste water, it is generally not recommended for cooking.