America’s public drinking water supply is among the cleanest in the world. Disinfected at the source, it’s free of disease-causing bacteria. But what if treatment facilities are offline? What if you get a boil order because of a water main break or have a private well that’s not treated with chlorine? Bacteria remain an ever-present health threat, so we’ll show you how to protect yourself with reverse osmosis technology.
Why Should You Worry About Bacteria in Drinking Water?
Millions die worldwide from waterborne bacterial illnesses, such as cholera and dysentery. As a country, we owe our bacteria-free water supply to disinfectants, like chlorine. Aggressive treatment usually makes water safe before it reaches your tap, but as always, there are exceptions.
The CDC estimates waterborne pathogens, including bacteria are responsible for 7,000 deaths and tens of thousands of hospitalizations in the US annually. And studies show that up to 40-percent of private wells are potentially contaminated with bacteria. Annual testing is recommended, but few homeowners follow through.
Our water safety is fragile. It depends on advanced technology and sound infrastructure to work, and when it doesn’t, you need a backup water purification method. What’s the solution? For many people, it’s a reverse osmosis system.
How Do Reverse Osmosis Filters Work?
Osmosis is the tendency of solvents, like water, to move across a semi-permeable membrane from areas of high concentration to areas of low concentration, thereby equalizing the number of molecules on each side.
Reverse osmosis changes the dynamic, using incoming water pressure to force water through a porous membrane that separates water from contaminants. Clean water is collected in a storage tank under your sink while contaminants from lead to bacteria go down the drain. It’s proven technology.
Water is dispensed from a special air-gap faucet that prevents the accidental backflow of contaminated water into the storage tank. As the stored water is used, more is produced, providing a consistent reservoir of 3-5 gallons at all times.
RO systems require an incoming water pressure of 60 PSI or greater to work without a booster pump. If you have a low-flow well or below-average city water pressure, you’ll need a model with an electric or non-electric permeate pump to enhance performance.
How Does Reverse Osmosis Remove Bacteria?
Reverse osmosis systems consist of prefilters plus an RO membrane laced with microscopic pores. Pore size averages 0.001-0.0001 microns — millionths of an inch. Bacteria range from 0.2-10 microns, so they can’t pass through.
What Other Contaminants Do Reverse Osmosis Systems Remove?
An RO membrane alone removes up to 99.9 percent of contaminants large than water molecules, including bacteria, parasites, and most viruses plus minerals, aqueous salts, like fluoride, and heavy metals like lead.
But because reverse osmosis membranes are sensitive to chlorine, sediment and high levels of some metal ions, most reverse osmosis filters are multi-stage systems that include a sediment and carbon filter. Not only are they protective, but they also expand the type of common contaminants an RO filter can remove.
The typical reverse osmosis system reduces:
- Industrial chemicals
- Pharmaceutical residue
- Bacteria, parasites and more
Depending on the pore size of the membrane, a better reverse osmosis filter can even eliminate most viruses.
Pros and Cons of Reverse Osmosis Systems
Like all water treatment systems, a reverse osmosis filter has advantages and disadvantages. Is it right for you? We will start with the pros.
#1 Contaminant Reduction
Reverse osmosis membranes struggle to remove hydrogen sulfide and chemicals, including pesticides and VOCs. But what they lack in capability, sediment and carbon prefilters make up for.
As water passes through multiple stages of filtration, more substances are removed. Few filters can compete with an RO system’s ability to remove contaminants that are serious health concerns.
Whole-house filtration systems require 12 square feet or more of space to install. Tall, they rarely fit in crawlspaces, so they take up valuable storage space in the basement or garage.
But most RO systems are point-of-use filters that only purify water from one tap for drinking and cooking. They fit beneath the kitchen sink where they’re out of the way and won’t ruin the room’s aesthetics.
#3 Ease of Installation
Whole-home filters are plumbed into your main water line — an RO system connects to the cold water line under your sink with an adapter. Not only is an RO system simple and economical to install — there’s no plumber required— but they’re also apartment-friendly and can go with you if you move.
An RO system costs more than a carbon-only filter, but there’s no better contaminant reduction for the money. You can purchase a well-equipped system for as little as $200. Compared to the price of bottled water, it’s a financial and ecological bargain.
See our Top list of Reverse Osmosis Systems.
The Cons of Owning a RO System:
An RO storage tank holds 3-5 gallons of water — plenty for drinking and cooking for most families. But a large group could run dry under heavy demand. As water is used, the system replenishes it. But the RO process is slow. Removing contaminants smaller than water molecules takes time, so most systems can purify a maximum of 20-125 gallons daily depending on the model.
#2 Water Pressure
The pressure in the RO storage tank is typically not as high as your normal incoming water pressure. One pet peeve among RO users is the slow trickle of water they get when water in the storage tank gets low. Expect better but not perfect performance from systems equipped with booster pumps.
Reverse osmosis filters remove most minerals from water, including calcium, magnesium and potassium. While we get all the minerals we need from eating food, water can taste flat without them. Taste is on the tongue of the beholder, however, and some people think it tastes better. Still, it may take some getting used to.
Reverse osmosis systems produce 1-3 gallons of wastewater for every gallon of pure water they make. If you drink city water, that not only adds to your water and sewer bill, but it’s also a problem for wells in drought-prone areas. With effort, the wastewater can be captured and repurposed for irrigation or other outdoor use, but it’s essentially a concentrated solution of contaminants that should be used cautiously.
Is an RO System Foolproof?
A reverse osmosis membrane that’s well-maintained and filtering properly can remove bacteria almost as effectively as a water treatment plant. While a few can slip through, the scientific consensus is that the amount won’t likely be enough to cause serious illness.
Some experts disagree, however, saying that home water filters are rarely maintained as well as public filtration systems. And they may be right. It’s important to note that many RO system manufacturers won’t guarantee that their products will remove bacteria and viruses because the expected reduction rate under normal conditions is less than 100-percent.
RO membranes are vulnerable to a wide range of contaminants, such as iron and chlorine, too much of which can damage a filter membrane irreparably. Forgetting to change the prefilters on time could compromise its performance.
If you’re using a reverse osmosis system to remove bacteria, maintenance is critical and having a secondary purification method is preferable. For complete protection, consider adding a UV light filter. It doesn’t remove bacteria, but it neutralizes it so that it can’t reproduce and cause disease. Combined with an ultraviolet light, a reverse osmosis system is virtually foolproof protection against bacteria and viruses.
Testing Water for Bacteria
Public water treatment authorities are quick to issue boil orders if they suspect there are bacteria in the water. But it doesn’t always happen in time. If you live in an area where these issues are common, you should be prepared to check your tap water for bacteria at home whenever your water quality changes.
For this purpose, inexpensive test strips or color-reagent test kits like pool owners use to check for chlorine offer peace of mind. If you install a reverse osmosis system, they’re also a good way to monitor its performance. Why be left wondering?
Wells, however, should be tested for bacteria by a certified laboratory at least annually. We recommend SimpleLab’s Tap Score test kit because it’s affordable, accurate and easy to use. They work with the best labs nationwide. Doing a comprehensive water test can also identify substances that can damage your RO system so that you can take precautions.
Does reverse osmosis remove bacteria? The short answer is that is does, but with conditions. A thoughtfully purchased, carefully maintained, and regularly monitored reverse osmosis system should keep your water bacteria-free.