Reverse osmosis
Reverse osmosis pushes water through a very fine membrane, giving you a dedicated tap for drinking and cooking. It’s a popular upgrade for better-tasting water and clearer ice and coffee.
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How it works
An under-sink system runs water through a sediment prefilter, a carbon filter, the membrane and usually a final polishing filter. Treated water collects in a small tank or, on tankless models, flows straight to a separate faucet. Some water goes down the drain during the process.
Under-sink or whole-house?
Most homes need under-sink reverse osmosis. Whole-house systems are much larger, cost far more and are usually reserved for unusual water. If you want every tap treated for taste and smell, whole-house filtration is generally a better starting point.
Before you install
- Check for space under the sink, plus a drain connection
- Hard or iron-heavy water can shorten membrane life, so pre-treatment may help
- Look at replacement filter prices and how often they’re due
- Ask for the system’s performance certifications, such as NSF/ANSI 58, and what they cover
Frequently asked questions
How much does reverse osmosis cost?
Under-sink systems usually cost $300–$1,500 installed. Whole-house systems run about $1,000–$8,000, based on national cost guides.
How often do filters need changing?
Prefilters are typically replaced every 6 to 12 months and membranes every few years, depending on your water and usage.
Does reverse osmosis waste water?
Some water goes to the drain to carry away what the membrane rejects. Newer systems use less, so ask for the system’s rated efficiency.
Can it connect to my fridge?
Often, yes. The line can usually be extended to a refrigerator for water and ice, depending on layout and pressure.