Reverse osmosis (RO) is widely considered the gold standard for residential drinking water purification. But how does it actually work, and is it the right choice for your home? This guide covers everything you need to know.
In simple terms, reverse osmosis forces water through a semi-permeable membrane with pores so small that virtually nothing except water molecules can pass through. The contaminants are flushed away, and clean water is stored in a tank for use.
A typical RO system has 4 to 7 stages of filtration:
Reverse osmosis is effective at removing:
The most common residential option. Water is filtered and stored in a pressurized tank (typically 3-4 gallons), ready for use. When you open the faucet, water flows from the tank.
Pros: Reliable, affordable, widely available Cons: Tank takes up space under the sink, water can taste stale if not used regularly
A newer design that filters water on demand without a storage tank. Higher flow rates and fresher water, but requires more powerful pumps.
Pros: Compact, fresh water on demand, continuous supply Cons: Higher upfront cost, requires electricity, slightly louder during use
Portable units that sit on your counter and connect to the faucet. Good for renters or those who cannot modify plumbing.
Pros: No installation, portable, affordable Cons: Lower capacity, takes up counter space, slower filtration
The system installs under your kitchen sink and includes a dedicated faucet mounted on the countertop. Installation typically takes 1-2 hours for a professional.
What is included:
Many homeowners connect their RO system to the refrigerator for filtered water and ice. This requires an additional line from the RO system to the fridge.
RO systems require regular filter changes to maintain performance:
An RO system produces water for approximately $0.02-$0.05 per gallon, compared to $1-$2 per gallon for bottled water.
Traditional RO systems produce 3-4 gallons of wastewater for every gallon of purified water. Modern high-efficiency systems have improved this to a 1:1 or even 2:1 ratio. The wastewater can be diverted to garden irrigation.
Yes, RO removes dissolved minerals including calcium and magnesium. However, the amounts in drinking water are nutritionally insignificant compared to what you get from food. If you prefer mineralized water, a remineralization stage adds them back.
Pure RO water has a slightly acidic pH (around 6.5) because it absorbs carbon dioxide from the air. An alkaline post-filter can raise the pH if desired. In practice, this slight acidity has no health impact.
Reverse osmosis is ideal if you:
Contact us to learn about our RO system options, or schedule a free water test to find out exactly what contaminants an RO system would remove from your water.
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