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Why trust this? A licensed plumber’s breakdown — real install costs, not equipment-only sticker prices.
Quick answer
A typical under-sink reverse osmosis install lands around $200–$1,000 all-in, with most jobs near $300–$600. The number breaks into two parts — the equipment and the install:
- Equipment: ~$150–$600 for a quality under-sink unit (budget tank systems start low; premium tankless run higher).
- Plumber labor: ~$100–$300 for a clean swap on an existing faucet hole · ~$300–$600+ if a new hole must be drilled in stone or a new drain line run.
- DIY: a confident homeowner can fit a kit for the equipment cost plus ~$20–$40 in fittings.
A whole-house RO system is a different, far pricier job (~$1,000–$4,800). Figures per HomeGuide, This Old House, Modernize & Angi (2026), anchored to Plumbing Picks’ Cost Index.
⭐ A PLUMBER’S TOP PICK
Ready to buy the unit itself? An under-sink RO system is the everyday pick for most homes: Best Under-Sink RO Systems →
What you’re actually paying for
Reverse osmosis pricing trips people up because the box price online is only half the story. There are really three line items: the equipment, the install, and the ongoing filters nobody mentions at the register. Here’s how each one shakes out in 2026.
1) Equipment (by system type)
- Standard under-sink RO (with tank) — ~$150–$400. The most common setup: a 3–5 stage unit and a small pressurized tank that lives under the sink. Best value for most homes.
- Tankless under-sink RO — ~$350–$600+. Higher flow, no bulky tank, often a higher-efficiency membrane — you pay a premium for the space savings and faster fill.
- Whole-house (point-of-entry) RO — ~$1,000–$6,000 for equipment alone, and a $1,000–$4,800 installed job. This is a major system most homes don’t need — if that’s what you’re weighing, see our cost to install a whole-house water filter guide.
2) Installation (labor)
- DIY — $0 labor plus ~$20–$40 in fittings. An under-sink kit ships with the membrane, filters, tank, faucet and tubing; you tap the cold supply with the included valve and clamp a drain saddle to the tailpiece. Two to four hours for a confident homeowner.
- Plumber, simple — ~$100–$300 when there’s an existing faucet hole (or a sprayer hole to repurpose) and an accessible cold-water line.
- Plumber, complex — ~$300–$600+ if a new hole has to be drilled through a granite or quartz countertop, a new drain connection or air-gap faucet is added, or access under the sink is tight.
2026 labor figures per HomeGuide (~$200–$500 typical), This Old House (point-of-use installs from ~$150, with DIY on a small unit saving roughly $100–$300 in labor), and Modernize (~$100–$500). The spread is almost entirely about the countertop hole and the drain.
3) The ongoing cost people forget
RO is the rare filter with a real running cost. Budget ~$50–$100 a year for the sediment and carbon pre/post filters (most homes swap them every 6–12 months), plus an RO membrane every 2–4 years at ~$50–$100. It’s not much, but it’s the true price of the water — factor it in before you buy.
Cost by system type (2026)
| System | Equipment | Install (plumber) | Typical all-in |
|---|---|---|---|
| Under-sink RO (tank) | ~$150–$400 | ~$100–$300 | ~$250–$700 |
| Under-sink RO (tankless) | ~$350–$600+ | ~$150–$350 | ~$500–$1,000 |
| With new countertop hole drilled | (as above) | +$150–$300 | add to the above |
| Whole-house (point-of-entry) RO | ~$1,000–$6,000 | built into job | ~$1,000–$4,800 |
DIY or hire a plumber? (the honest line)
- DIY makes sense for a standard under-sink kit where you already have a faucet/sprayer hole and an accessible cold-water shutoff. The connections are clamp-on and push-fit by design — this is one of the more DIY-friendly water jobs there is.
- Hire a plumber when a new hole has to go through a stone countertop (a cracked granite top dwarfs the service call), when the drain or supply tie-in isn’t straightforward, or when you want an air-gap faucet to code. The rule I give homeowners: if a slip damages the countertop or means water inside the cabinet base, pay for the install.
What drives the price up or down
| Factor | Cheaper | More expensive |
|---|---|---|
| System type | Standard tank unit | Tankless / high-capacity |
| Faucet hole | Existing hole reused | New hole drilled in granite/quartz |
| Drain & supply | Accessible, simple tie-in | New drain saddle / air-gap faucet |
| Labor | DIY | Plumber + countertop drilling |
| Membrane / stages | 3–4 stage standard | 5+ stage, remineralization, UV add-on |
A plumber’s take
The under-sink RO unit itself is genuinely cheap and genuinely DIY-able — that part’s real. Where the budget moves is the countertop. If your sink has a spare hole or a sprayer you’re willing to give up, you’re in great shape and a $250 job stays a $250 job. The moment someone has to drill a fresh hole through granite or quartz, you’ve got a different cost and a different risk, and that’s the one place I tell homeowners to stop and call a pro. The other thing I’d plan for is the filters: RO water isn’t free water — it’s about $50–$100 a year to keep it tasting right. Buy the system knowing that, and you’ll be happy with it for a decade.
Bottom line
For most homes, an under-sink reverse osmosis system is a $250–$700 project — one of the best value-per-dollar upgrades in clean drinking water, and a reasonable DIY if the countertop cooperates. Decide on the unit first, then decide DIY versus pro based on whether a new countertop hole is involved. When you’re ready to choose a system, here are our tested picks → Best Under-Sink Reverse Osmosis Systems.
Still deciding whether RO is even the right tool? Compare it head-to-head: reverse osmosis vs. a water softener (they solve different problems — many homes run both) and water distiller vs. reverse osmosis. And if you’re weighing softener install costs too, see what a water softener costs to install.
Frequently asked questions
How much does it cost to install a reverse osmosis system?
A typical under-sink (point-of-use) reverse osmosis system runs about $200 to $1,000 all-in, with most jobs landing near $300 to $600. The equipment is roughly $150 to $600 (budget units start low; premium tankless units run higher) and a plumber’s labor is about $100 to $300 for a clean swap that uses the existing faucet hole, more if a new hole has to be drilled in stone or a new drain line run. 2026 figures per HomeGuide, This Old House, Modernize, and Angi. A whole-house (point-of-entry) RO system is a different, far pricier job at roughly $1,000 to $4,800 installed.
Can I install an under-sink RO system myself?
Yes, a confident DIYer can usually install an under-sink RO kit in two to four hours for just the equipment cost plus about $20 to $40 in fittings. The kit comes with everything but the connections, and most units tap the cold supply with a self-piercing or quarter-turn valve and clamp a drain saddle to the sink tailpiece. The one job worth a pro is drilling a new faucet hole through a granite or quartz countertop, where a cracked top costs far more than the service call.
How much does a plumber charge to install a reverse osmosis system?
Roughly $100 to $300 in labor for a straightforward under-sink install that reuses an existing faucet hole and an accessible cold-water connection, per HomeGuide, This Old House, and Modernize 2026 data. Plan on $300 to $600 or more if the plumber has to drill a new hole in a stone countertop, run a new drain connection, or add an air-gap faucet. For comparison, Plumbing Picks’ Cost Index lists a whole-house water-softener tie-in at $1,000 to $3,000 installed, so a point-of-use RO is one of the cheaper water-treatment installs.
What does an RO system cost to maintain each year?
Budget about $50 to $100 a year for the sediment and carbon pre/post filters, which most homes change every six to twelve months, plus an RO membrane every two to four years at roughly $50 to $100. That ongoing cost is the real price of RO water and is worth factoring in before you buy. Tankless units and higher-capacity membranes can stretch the replacement interval.
Related plumbing cost guides
Pricing another project? These plumber-written cost breakdowns use the same real-world, source-checked numbers — no national-average guesswork:
- Cost to install a whole-house water filter
- Cost to install a water softener
- Cost to install a sump pump
- Cost to install a faucet
- Cost to install a bidet
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