Everything you need to know about reverse osmosis water filter systems

If you’ve been considering an upgrade to your tap water—or you’re looking for a long-lasting, lower-waste option for purified water without plastic bottles—then reverse osmosis filtration systems should be on your radar.

Reverse osmosis filtration systems, or RO systems, are popular options for people looking to make their water clearer and tastier, and to filter it so that it is free of harmful chemicals, excessive minerals, and viruses and bacteria. There are several options, with models ranging from countertop standalone units to whole-house systems.

However, there are advantages and disadvantages you need to take into account. If you’re reading to upgrade from your standard water filter pitcher, here’s what you need to know.

What is reverse osmosis anyway?

Reverse osmosis filters work by creating pressure that forces incoming water through a semi-permeable membrane that removes contaminants from the treated water while creating a stream of waste water called brine or concentrate that contains everything that was removed.

The reverse osmosis process can catch smaller particles and molecules than a physical filter can alone, including things like dissolved chemicals and even bacteria and viruses, making it an excellent choice for treating water in the home.

What role does a reverse osmosis filter have in the home?

Installing a reverse osmosis filter can make a measurable difference in your water quality by ensuring a continuous supply of clean, purified water without relying on plastic bottles. Users concerned about harmful chemicals or contaminants in their water—or who don’t like the taste or clarity of the water in their home—can rest assured that foreign particles and solids, as well as chemicals like chlorides and fluoride, are efficiently removed.

Step by step: Here’s how RO filters purify water

Most RO filtration systems have three, four, or five filters. Almost all systems include:

• A sediment prefilter that removes particles and sediment
• An activated carbon prefilter that removes chemicals, including chlorine and fluoride
• A reverse osmosis membrane that takes out dissolved solids, including lead

They can also include: - Additional carbon filters that come before or after the reverse osmosis membranes - UV filters to kill any remaining bacteria or viruses - A remineralizing cartridge that adds back a calibrated mix of helpful minerals to rebalance the water for optimal mineral content for health benefits and crisper taste

What are the benefits of using an RO water filter system in the home?

Considering adding filtration? There are several reasons a reverse osmosis water filtration system might be a great addition to your home.

Health advantages

If you live in an area with poor water quality, you may already be using other water filters like activated carbon filters, UV filters and/or ceramic filters in filter pitchers, or on-faucet filters. However, if your local water is known for poor quality, you need to ask whether water filters remove contaminants. Chemicals like lead, arsenic, and chlorine can be harmful in elevated levels, and even water that comes from a treatment plant has to run through pipes that can introduce chemicals, viruses, or bacteria. RO filter systems ensure your water is being filtered directly before your use.

Taste improvement

Water’s taste is created by many things: The minerals in the water, additives from the water processing source that inhibit the growth of bacteria and mold, and any residue from the pipes the water is carried through. If any of these factors create a taste you don’t like, a reverse osmosis system may be the answer, as it filters out things like excessive calcium or magnesium, dissolved salts, chlorine, or any other elements that may contribute to an unpleasant taste.

Some users find that reverse-osmosis-purified water tastes flat after all minerals are removed (although some prefer this purer taste)—in this case, looking for an RO system that includes a remineralization step can create the water taste they prefer.

Price and cost savings

The cost of a reverse osmosis system varies significantly depending on the type of system you choose.

Countertop models are standalone units that sit in your kitchen or bathroom and filter the water you add to their tanks. Prices range from $150 to $500.

Under-sink systems or point-of-use systems are designed to filter the water for a single sink. These systems generally run from $100 to $500, with prices varying depending on whether you buy a three-step or five-step filter process or a system with or without a tank.

Whole-house reverse osmosis systems or point-of-entry systems vary in price, as well, with some options starting under $1,000 but going as high as $20,000 or more, with many options in the $2,000 to $3,000 range.

Whether you opt for an under-sink model or a whole-house model, there are additional costs to consider. While some systems can be installed by the buyer directly, others will require professional installation, which can cost $200 or more (sometimes much more) depending on your region and the complexity of the system.

No matter what system you use, you’ll need to purchase replacement filters and membranes according to your system's suggested schedule. Filters vary in price, from as little as $20 for a single replacement to more than $200.

The final additional cost to consider is a potential increase in your water bill, as RO systems create wastewater with every gallon of purified water they make. Depending on the price of water in your area, this extra water could be a small or a significant expense to consider.

Things to know about installing a home reverse osmosis system

While some reverse osmosis systems will need the services of a professional to install (whole home systems generally need to be left to the pros), there are a few that don’t.

Countertop models need no installation and can be set up and used like any other small appliance in the kitchen. Many under-sink models can be installed by anyone comfortable with basic plumbing–the filter system will need to be attached to the cold water supply with tools like a drill and a screwdriver. Check your model’s instruction manual for additional details.

Maintenance and care

Reverse osmosis water filter systems need regular care and maintenance to continue to operate efficiently and effectively—and to prolong the life of your investment.

In general, most systems recommend four types of regular maintenance: changing the filters (often every six months to a year); changing the membrane (every few years); sanitizing the system (when you change the filters or every year); and draining the storage tank (when you change the filters).

While these are general guidelines, specific systems will have their own maintenance best practices. Refer to the owner's manual for your model for more specific instructions on how to care for your filter system.

Are there any environmental impacts to using an RO system

Reverse Osmosis systems have both positive and negative impacts on the environment—but in our opinion, there are more upsides than downsides.

In the negative column, RO systems create waste water in the process of purification that contains the impurities that have been filtered out of the clean water. Some systems say they create approximately one gallon of waste water for each purified gallon created; many systems average between three and five gallons for each purified gallon. The most inefficient systems create as many as 10 gallons of waste water per purified gallon, which is often sent down the drain.

The wastewater produced by RO filtration isn’t greywater, like the waste water created in sinks, showers, and washing machines—because of the reverse osmosis filtration process, it contains a much higher concentration of minerals, bacteria, and particulate than normal tap water. (It contains, in fact, all of the things removed from the purified water.)

However, if you set up a tank to hold the waste water created by your system—and, crucially, test it to make sure its level of total dissolved solids (TDS) doesn’t make it unfit for any use—RO filter waste water can be used to water non-edible plants, flush toilets, and mop floors to mitigate the impact.

The upside of RO filtration systems is how much waste they can help users avoid. The average American drinks approximately 26 gallons of bottled water a year—the equivalent of 208 single-serving 16.9-ounce water bottles each. When you consider that one plastic water bottle uses 9.25 grams of plastic, the impact of replacing bottled water with filtered water is significant.

In addition, using a reverse osmosis system can help cut down on the amount of microplastics in your life and the environment. Given that a liter of bottled water (two average-sized water bottles) contains 240,000 pieces of microplastic, using water that bypasses plastic bottle storage entirely can make a measurable difference in microplastic exposure.

Our Experts

I’m Jennifer Ernst Beaudry, a reporter who’s covered consumer goods, including all things home and garden, for more than 15 years.

Resources

• Culligan Water of Denver
• National Institutes of Health, Plastic particles in bottled water
• International Bottled Water Association, Bottled water packaging has the lowest environmental footprint of all packaged drinks.
• Centers for Disease Control, How water treatment works
• Waterdrop, Is the Wastewater Produced by the RO System Really Wasteful?