If you want the cleanest, best-tasting drinking water possible in your home, reverse osmosis is the answer. It is the same technology used to produce pharmaceutical-grade water, hospital dialysis water, and the bottled water you buy at the grocery store. And at residential scale, it is one of the most cost-effective upgrades a Twin Cities homeowner can make.
This guide breaks down exactly how reverse osmosis works, what it removes from your water, when it makes the most sense, and what East Metro homeowners specifically need to know before installing a system.
What Reverse Osmosis Actually Is
Reverse osmosis is a water filtration technology that uses a semi-permeable membrane to physically separate dissolved contaminants from water. It is the most thorough form of residential water purification available.
The system works by forcing water through a membrane with microscopic pores roughly 0.0001 microns in diameter. To put that in perspective:
- A human hair is about 70 microns wide
- A bacterium is about 1 micron wide
- A virus is about 0.1 micron wide
- An RO membrane pore is 1,000 times smaller than a virus
At that scale, almost nothing gets through except water molecules. Dissolved minerals, heavy metals, chlorine byproducts, pesticides, PFAS, sodium, and most organic contaminants are physically rejected by the membrane and flushed to the drain.
The result is water that is roughly 95 to 99 percent free of dissolved contaminants, depending on the system and the source water.
How a Residential RO System Is Built
A standard under-counter residential RO system consists of four to six stages working in sequence:
- Sediment pre-filter to remove sand, rust, and particles
- Carbon pre-filter to remove chlorine, which would damage the membrane
- Second carbon pre-filter for additional protection and taste improvement
- RO membrane for the actual purification stage
- Carbon post-filter for final polish
- Optional mineralization stage to add back trace minerals for taste
Treated water is held in a small pressurized tank under the sink, typically holding two to four gallons. When you turn on the dedicated RO faucet at the sink, treated water flows out at usable kitchen pressure.
Most systems also include connections for your refrigerator water and ice maker, which means every glass of water, every ice cube, and every coffee pot starts with the cleanest possible water.
What an RO System Removes
Reverse osmosis is the broadest-spectrum residential water filtration available. Verified contaminants removed by a properly maintained RO system include:
- Lead, arsenic, and other heavy metals
- PFAS chemicals when paired with NSF/ANSI 58 certification
- Chlorine and chloramine
- Fluoride
- Nitrates and nitrites from agricultural runoff
- Sulfate
- Sodium, including the trace sodium added by a water softener
- Total dissolved solids by 95 to 99 percent
- Pharmaceutical residue
- Pesticide and herbicide residue
- Most volatile organic compounds
- Bacteria and viruses (dedicated UV recommended for well systems)
This is dramatically more thorough than any pitcher filter, refrigerator filter, or basic carbon filter on the market.
Why RO Makes Sense for Twin Cities Homes
Several characteristics of Twin Cities water make reverse osmosis particularly valuable in this market.
Centrally softened cities
Cities like Saint Paul, Bloomington, Eden Prairie, Richfield, Robbinsdale, and most cities served by the Joint Water Commission deliver centrally softened municipal water. Central softening adds sodium and leaves chlorine, chloramine, and dissolved solids in the water. An RO system at the kitchen tap removes all of these and produces clean drinking water.
Hard water cities with home softeners
If your home has a water softener, the softening process trades calcium and magnesium for sodium. Most healthy adults can drink softened water without issue, but the trace sodium can be a concern for low-sodium diets, infant formula, and certain medical conditions. An RO system removes that sodium and gives you flexibility.
East Metro PFAS zone
For homes in the documented PFAS contamination zone, an NSF/ANSI 58 certified RO system is the most reliable point-of-use protection against PFAS contamination. This includes cities like Bayport, Lake Elmo, Lakeland, Cottage Grove, Woodbury, and surrounding communities. See our PFAS filtration page for more detail on the East Metro contamination zone.
Private well users
Homes on private wells in the East Metro, Anoka County, Dakota County, and the St. Croix Valley often deal with multiple contaminant issues at once. RO addresses dissolved contaminants comprehensively in one system.
Chlorinated city water
Saint Paul Regional Water Services and most municipal systems use chlorine or chloramine for disinfection. RO removes these along with their byproducts, producing water with a noticeably cleaner taste.
The Cost vs Value Equation
A quality residential RO system installed in the Twin Cities typically costs between 600 and 1,800 dollars, depending on the system, the brand, and installation complexity.
Most homeowners who run the numbers find that RO pays for itself within 1 to 3 years compared to bottled water consumption. A family that buys two cases of bottled water per week spends roughly 1,000 dollars per year on bottled water. An RO system replaces that completely with on-demand water from your own tap.
Annual maintenance costs for an RO system are typically 75 to 150 dollars for replacement pre-filters and post-filters, with the RO membrane itself replaced every 2 to 5 years at around 75 to 150 dollars depending on the brand.
Common Misconceptions About RO
Does RO remove all the minerals I need from drinking water?
RO removes most dissolved minerals from water. This is the right outcome, since the calcium and magnesium in tap water are not significant nutritional sources. Mineralization stages can be added to RO systems if you prefer the taste of mineralized water, but the human body gets its essential minerals from food, not water.
Is the wastewater from RO bad for the environment?
Older RO systems sent two to four gallons of wastewater to the drain for every gallon of treated water. Modern systems have dramatically improved this ratio, with many systems now operating at 1:1 or better.
Does RO water taste flat or strange?
This is purely a matter of acclimation. Most people who try genuinely clean RO water find that tap water suddenly tastes off by comparison. If you prefer a slight mineral character, a remineralization filter can be added as the final stage.
Do I need RO if I already have a water softener?
A softener and an RO system address different problems and work together. The softener handles whole-home hardness. The RO handles drinking water quality, dissolved contaminants, and PFAS protection. The combination is the gold standard for residential water treatment.
Will RO remove fluoride?
Yes. RO is one of the few residential filtration technologies that effectively removes fluoride.
Sizing and Capacity
Residential RO systems are measured in gallons per day of treated water production. Common sizes include:
- 50 GPD systems: Good for households of 2 to 4 people with normal drinking water use
- 75 GPD systems: Good for households of 4 to 6 people, or homes with heavy ice maker and coffee maker use
- 100 GPD systems: Good for larger households or households with multiple refrigerator connections
Installation Considerations
A standard residential RO installation involves mounting the multi-stage filter housing under the kitchen sink, installing the storage tank, drilling a hole for the dedicated RO faucet, connecting to the cold water supply, tapping into the drain line, and optionally running a line to the refrigerator water and ice maker. Most installations take 1 to 3 hours for a professional installer.
How to Choose the Right System
The features that actually matter when comparing systems:
- NSF certifications: Look for NSF/ANSI 58 at minimum. For PFAS protection, NSF/ANSI 53 for PFOA and PFOS is required.
- Filter accessibility: Quick-change filter cartridges are dramatically easier to maintain than older wrench-style housings.
- Replacement filter cost and availability: Open-standard systems use industry-common cartridges that are easier and cheaper to source.
- Local service availability: Buying from a local water treatment company means you have someone to call when service is needed.
Frequently Asked Questions
How long does an RO system last?
A properly maintained residential RO system typically lasts 10 to 15 years. The membrane is replaced every 2 to 5 years. Pre and post filters are replaced annually.
Can I install an RO system myself?
Some homeowners do, but professional installation is recommended. Proper installation ensures the system is sealed correctly, the drain saddle is positioned to prevent backflow contamination, and the pressure regulator settings match your home's water pressure.
Will RO improve my coffee and tea?
Significantly. Coffee and tea flavor depends heavily on water quality. RO water produces noticeably cleaner, brighter flavor in both. Many specialty coffee shops use RO water specifically for this reason.
Is RO water safe for babies?
Yes. RO water is safe for infants and is actually recommended by many pediatricians for mixing formula due to its low contamination levels.
Can I connect RO to my refrigerator?
Yes, and this is one of the highest-value uses of an RO system. Most installations include a connection line to the refrigerator water dispenser and ice maker, which means every glass and every ice cube starts with purified water.
The Bottom Line
Reverse osmosis is the most effective residential water purification technology available today. For Twin Cities homeowners, it solves multiple problems at once: chlorine and chloramine taste, dissolved solids, sodium from softened water, PFAS protection in affected areas, and overall water quality at the kitchen tap.
For most homes, the right setup is a salt-based water softener for the whole house combined with a reverse osmosis system at the kitchen sink. This combination handles every common water quality issue in the Twin Cities and produces water that is measurably superior to anything you can buy in a bottle.
Use our Water Quality lookup tool to check the hardness and water profile for your specific city. See our full service area to confirm we cover your neighborhood.
Ready for the Cleanest Water in Your Home?
AJ Alberts installs NSF-certified reverse osmosis systems across the Twin Cities. Free in-home water test, no obligation.