How much does an under-sink reverse osmosis system cost?

$300 to $950 installed. The spread is mostly stage count and what your kitchen cabinet and counter require, not the brand on the housing.

Do I need reverse osmosis on Bellingham city water?

It is a preference rather than a necessity. Bellingham draws its drinking water from Lake Whatcom and treats it, so reverse osmosis here is typically about taste, chlorine by-products and dissolved solids rather than safety. On a private well the reasoning is different, and it starts with a water test rather than with equipment.

Is there a rebate for a water filtration system?

No. We are not aware of any PSE, Community Energy Challenge, Opportunity Council or state programme in Whatcom County that pays for drinking water treatment, and the federal credits that terminated at the end of 2025 never covered it either. We would rather say so than imply there is money on the table.

How much water does it waste?

Reverse osmosis sends some water to the drain to carry away what the membrane rejects, and the ratio depends on the unit and your pressure. A permeate pump improves it noticeably on low-pressure supplies. If wastewater is your main concern, a carbon filtration system with no reject stream may suit you better.

Should I get whole-house reverse osmosis instead?

Almost never, for drinking water. Whole-house reverse osmosis is published at $4,800 to $8,000 installed and treats every gallon you flush and shower with, which is a great deal of membrane for a small amount of drinking water. Filter the whole house for what the whole house needs, and use reverse osmosis at the tap you drink from.

How often do the filters need changing?

Pre-filters regularly and the membrane rarely, and the schedule depends on your water rather than on the calendar. We set the interval to the unit we install and to whether you are on treated city water or a well. We will also show you how to change them yourself if you would rather not pay for a visit.

Installed price · verified 2026-09-04

Reverse osmosis system cost

$300–$950 Under-sink reverse osmosis system, installed. The same source prices whole-house reverse osmosis at $4,800–$8,000, which is a different machine for a different problem and is covered on our whole-home water filtration page., before rebates. Here is what decides where in that range your house lands.

Call (360) 592-3824 Get a free estimate or text us

Reverse Osmosis System Cost — Under-Sink Drinking Water in Bellingham

Under-sink reverse osmosis system, installed. The same source prices whole-house reverse osmosis at $4,800–$8,000, which is a different machine for a different problem and is covered on our whole-home water filtration page.

Simple job: $300
Complex job: $950

Installed price before rebates — equipment, labour, materials, permit and startup. The federal §25C tax credit contributes $0 in 2026: it terminated for anything placed in service after December 31, 2025.

Range benchmarked 2026-09-04 against published local pricing. Your quote is fixed before work starts — no hourly surprises.

WA L&I #BELLIHC808NM Active registration — verify it with the state
$30,000 bonded Surety bond on file with L&I
$1,000,000 insured General liability coverage
Local since 2020 Owner-operated in Whatcom County
We pull the permit City of Bellingham or Whatcom County, and we meet the inspector

What moves your number

Most impactful first. These are the questions we ask on the phone, and they are the reason a range exists at all.

Stage count and membrane capacity: most of the spread between $300 and $950; A three-stage unit with a small membrane and a simple tank sits at the bottom of the range; a five-stage system with a remineralisation stage, a larger membrane and a permeate pump sits at the top. More stages mean more cartridges to change later, so there is a running cost attached to the up-front choice. We would rather fit a system you will actually maintain.
What is under the sink already: a cabinet with room and an accessible cold line keeps the install at the low end; Reverse osmosis needs a cold supply tap, a drain saddle, somewhere for the tank to sit upright and a hole in the deck or sink for the faucet. A mid-2000s kitchen with a deep cabinet and a spare deck hole is quick. A 1920s kitchen with a shallow cabinet, a cast-iron drain and a solid-surface counter needs a faucet hole drilled and the tank relocated, which is where the labour goes.
Faucet and drain details: a designer air-gap faucet or a drilled counter adds to the material and labour; The dedicated faucet is a visible fixture, and people care what it looks like, which is fair. Matching a finish and drilling a granite or quartz counter is more work than dropping a chrome faucet into an existing hole. The drain connection also has to be made correctly so the reject water cannot siphon back.
Water pressure at the tap: a permeate pump or booster is an added component where pressure is low; Reverse osmosis membranes need incoming pressure to work, and production falls off sharply when they do not get it. Houses at the top of a hill, on a long private line, or on a well with a marginal pressure tank sometimes need a booster or permeate pump. It is cheaper to identify that at the quote than to explain a trickling faucet afterwards.
Filter replacement over time: an ongoing annual cost rather than an install cost; Sediment and carbon pre-filters get changed regularly and the membrane much less often, and neglecting the pre-filters is what kills membranes early. Households on well water typically go through pre-filters faster than a Bellingham house on treated Lake Whatcom water. We will tell you the actual cartridge schedule for the unit we fit.

What appears on a real quote

Line by line, the way we scope it. If a quote you are holding is a single lump sum, this is the list to ask them to break out.

Reverse Osmosis System Cost — Under-Sink Drinking Water quote line items and typical ranges in Bellingham, WA
Line item	Typical range	What it is
Under-sink reverse osmosis system, installed	$300–$950	HomeGuide.
Dedicated drinking-water faucet	included; upgraded finishes are priced on request	—
Cold-line tap, drain saddle and tubing	included	—
Counter or sink-deck hole for the faucet, where one does not exist	added labour; stone counters are drilled with the right tooling or by a stone fabricator	—
Storage tank placement and support	included	—
Permeate or booster pump for low-pressure supply	an added component where pressure testing shows it is needed	—
Startup, flush and leak check	included	—
Replacement cartridge set	ongoing; scheduled to the unit we install	—

Line items are quoted against your house, not averaged. Your written quote is fixed before work starts.

Three worked examples

Same work, three different houses. The arithmetic runs from the installed price, through the programs that apply, to what you write a cheque for.

Three-stage under-sink system in a Bellingham kitchen with a spare deck hole and room in the cabinet

Installed price: $450
Rebates applied: No rebate or tax credit applies to drinking water treatment
You pay: $450

No incentive programme in Whatcom County pays for water treatment, and the federal energy credits never covered it even before they terminated.

Five-stage system with remineralisation and a matched faucet in a remodelled kitchen with a quartz counter

Installed price: $900
Rebates applied: None
You pay: $900

Near the top of the published range. The counter drilling and the faucet finish are most of the difference from the basic install.

Under-sink system for a north county farmhouse on well water, sediment pre-filtration added ahead of it

Installed price: $700 for the reverse osmosis system, plus whole-house pre-filtration quoted separately
Rebates applied: None
You pay: $700 plus the pre-filtration scope

On well water, protecting the membrane is the whole game. North county wells carry sediment and iron that will shorten a membrane’s life quickly, so the honest answer is often a whole-house pre-filter feeding a modest reverse osmosis unit at the sink.

No example includes a federal tax credit, because there is none to include for a 2026 install. The largest single line in most of these is Puget Sound Energy's $1,500 electric-resistance conversion rebate, which is contractor-gated — PSE requires the installer to be inside its network, so ask us to confirm status for your project before you count on it.

Run your own numbers

A range, not a quote — and the arithmetic is shown so you can check it. Every band below is a published installed price, linked at the bottom.

Sources, all checked 2026-09-04: ductless by zone, ducted in Bellingham, local aggregator range, panel upgrade, dedicated circuit, heat pump water heater. Electrical work is performed and permitted by a licensed electrical contractor — we hold a general contractor registration, not an electrical one.

The work itself

Reverse Osmosis Drinking Water

Drinking water that tastes like water, chosen on the basis of what is actually in your supply rather than what a catalogue says.

See how we do it — process, permits, equipment and timeline →

Talk it through — (360) 592-3824

Reverse Osmosis System Cost — Under-Sink Drinking Water — questions we get asked

How much does an under-sink reverse osmosis system cost?: $300 to $950 installed. The spread is mostly stage count and what your kitchen cabinet and counter require, not the brand on the housing.
Do I need reverse osmosis on Bellingham city water?: It is a preference rather than a necessity. Bellingham draws its drinking water from Lake Whatcom and treats it, so reverse osmosis here is typically about taste, chlorine by-products and dissolved solids rather than safety. On a private well the reasoning is different, and it starts with a water test rather than with equipment.
Is there a rebate for a water filtration system?: No. We are not aware of any PSE, Community Energy Challenge, Opportunity Council or state programme in Whatcom County that pays for drinking water treatment, and the federal credits that terminated at the end of 2025 never covered it either. We would rather say so than imply there is money on the table.
How much water does it waste?: Reverse osmosis sends some water to the drain to carry away what the membrane rejects, and the ratio depends on the unit and your pressure. A permeate pump improves it noticeably on low-pressure supplies. If wastewater is your main concern, a carbon filtration system with no reject stream may suit you better.
Should I get whole-house reverse osmosis instead?: Almost never, for drinking water. Whole-house reverse osmosis is published at $4,800 to $8,000 installed and treats every gallon you flush and shower with, which is a great deal of membrane for a small amount of drinking water. Filter the whole house for what the whole house needs, and use reverse osmosis at the tap you drink from.
How often do the filters need changing?: Pre-filters regularly and the membrane rarely, and the schedule depends on your water rather than on the calendar. We set the interval to the unit we install and to whether you are on treated city water or a well. We will also show you how to change them yourself if you would rather not pay for a visit.

Get the number for your house

A range tells you whether to keep reading. Tell us about the house and we will tell you which end of it you are at, what the rebates take off, and what the written quote will say.

Range benchmarked 2026-09-04 against published local pricing · All published cost ranges

Ready for a straight answer on your house?

Tell us what you have now and what you want it to do. We will tell you what fits, what it costs, and which rebates you actually qualify for — before anyone comes out.

Monday–Friday, 8:00 AM – 5:30 PM · Emergency calls answered 24/7

Call (360) 592-3824 Text us instead Book online →