Under-Sink Water Filter Cost: Installed Price Breakdown

A typical under-sink reverse osmosis filter costs $300 to $900 installed. That total includes the equipment and a standard plumbing connection to a dedicated kitchen faucet. Ongoing ownership adds roughly $60 to $150 per year for cartridges and membrane replacement.

What an Under-Sink Filter Costs Installed

Installed cost splits into two line items: the equipment itself and the labor to connect it. For an under-sink reverse osmosis (RO) system, equipment runs $200 to $600. Installation adds $100 to $300 for most straightforward under-cabinet setups, bringing the installed total to $300 to $900.

Non-RO under-sink carbon systems exist at lower price points, but they do not provide the same rejection performance. If your water test shows nitrate near the 10 mg/L limit or elevated total dissolved solids, RO is usually the appropriate under-sink technology. A lab water test costs $40 to $150 and is the first step before selecting equipment.

Equipment vs. Installation Split

Here is how the installed price typically breaks down:

Installation assumes an accessible cabinet, existing cold-water supply line, and a drain connection for RO waste. If the installer must run a new line, cut a countertop hole for the faucet, or address cramped plumbing, labor moves toward the top of that range or beyond.

Ongoing Costs Per Year

The purchase price is not the full ownership cost. Under-sink RO systems use pre-filters, a carbon post-filter, and a membrane. Replacement cartridges and membrane together run $60 to $150 per year, depending on water quality and usage.

Example arithmetic for a mid-range system:

• Sediment and carbon pre-filters: changed every 6–12 months
• Carbon post-filter: changed every 12 months
• RO membrane: replaced every 2–3 years

If pre-filters cost $40 per set and are replaced twice yearly, that is $80. A post-filter at $30 adds another $30. A membrane at $80 spread across three years adds roughly $27 per year. Total: about $137 per year, which sits inside the $60 to $150 estimate.

RO systems also send water to the drain. A typical waste ratio is 3–4:1, meaning three to four gallons are discharged for every gallon of filtered water stored. On a household using 3 gallons of RO drinking water per day, that is 9 to 12 gallons of waste daily, or roughly 3,285 to 4,380 gallons per year. This does not change the equipment price, but it affects water and sewer bills if those are metered.

Cost Comparison by Filter Type

Not all under-sink filters are RO. Simple carbon block systems cost less upfront but do not reduce dissolved minerals or nitrate. The table below compares installed cost and annual upkeep for common under-sink configurations.

If you are weighing under-sink versus whole-house treatment, remember that whole-house RO starts around $3,000 to $8,000 installed and is sized for flow rates of 8–15 GPM. An under-sink unit treats one point of use only, which keeps the installed cost low but does not protect appliances, fixtures, or shower water.

How to Size and Choose

Follow this sequence before buying:

1. Test the water first. A lab test ($40–$150) identifies hardness, iron, nitrate, and TDS levels.
2. Match the technology to the result. Nitrate at or near 10 mg/L, or high TDS, points to RO. Hardness alone may point to a softener instead, which costs $1,200 to $4,500 installed for whole-house equipment.
3. Confirm under-sink fit. Measure cabinet height, depth, and clearance for the storage tank, which is typically 11–15 inches tall.
4. Check drain access. RO needs an air gap or standpipe connection to the sink drain.
5. Compare installed quotes, not just equipment prices. A $250 system can cost $700 installed after labor and fittings.

For homes with hard water throughout the house, a water softener may be the larger priority. Softener equipment runs $600 to $2,500, with installed costs of $1,200 to $4,500. Salt runs $120 to $400 per year, and resin rebeds cost $300 to $600 every 8–12 years. That is a separate decision from an under-sink drinking filter, but the two are sometimes paired.

Hidden Costs and Maintenance Traps

The lowest advertised price often excludes items that show up on the final invoice. Common add-ons include:

• Dedicated faucet: $30–$100 if not included
• New drain saddle or air gap: $20–$60
• Shut-off valve replacement on old plumbing: $50–$150
• Cabinet modification or countertop drilling: variable by contractor

Skipping cartridge changes is the most expensive mistake. A clogged pre-filter reduces flow and can force the membrane to work harder, shortening its 2–3 year life. Sticking to the replacement schedule keeps the annual cost near $60 to $150 rather than forcing an early membrane purchase.

Bottom Line

Expect to pay $300 to $900 installed for an under-sink RO system, with $60 to $150 in annual filter and membrane costs. Test your water first, confirm cabinet and drain fit, and compare installed quotes rather than equipment-only prices. If your water quality issues extend beyond the kitchen sink, whole-house options such as softeners, carbon filtration, or whole-house RO carry much higher installed costs and should be evaluated separately.

Next, compare how much does a water softener cost, water softener installation cost, whole house water filter cost before you commit.