If you’re handy, an under-sink unit can be installed in an afternoon with a drill and a YouTube video, saving you about $100 to $300 in labor. But plumbers are wizards, and wizards charge accordingly: expect $150 to $500 for professional installation, especially if you need a new faucet hole or a drain line.
Pro tip: Before you buy, check your water pressure. Most RO systems need at least 40 psi to work efficiently. If your pressure is low, you might need a booster pump—that’s another $200 to $400, but it’s like upgrading from a bicycle to an e-bike for your plumbing.
How Much Does a Reverse Osmosis System Cost? (2026)
The Water Waste: The Unseen Cost
Here’s a sobering stat that might make you rethink your morning pour: traditional reverse osmosis systems waste about 3 to 4 gallons of water for every gallon they produce. That’s not just a water bill spike (roughly $10 to $30 more per month in cities with high rates)—it’s a karmic footprint.
Newer high-efficiency models cut that waste to a 1:1 ratio, but they cost 20% to 40% more upfront. It’s a classic case of spending money to save water, like buying a Prius to feel better about your commute.
Fun fact: That wasted water—called “reject water”—is completely clean enough to water your houseplants or flush your toilet. You can rig a system to capture it, and suddenly you’re the eco-chic neighbor with the thriving ferns.
