Tank Reverse Osmosis System

Our tank reverse osmosis system is $800 installed in Eastern Iowa, and it is the drinking-water system we put on private wells. It stores treated water so the membrane never has to keep pace with the faucet, which is the whole reason it is the one we put on a well; it is also the pick for city homes that would rather pour from a stored supply. This page covers the unit itself. The general case for reverse osmosis at the kitchen tap, what it removes and how it tastes, is on our reverse osmosis drinking water page.

What goes into the cabinet

Three pieces: a filter assembly mounted on the cabinet wall, a storage tank on the cabinet floor beside it, and a dedicated faucet at the sink deck. Five stages are mounted in the wall assembly: two prefilters, the 100-gallon-per-day membrane, a polishing stage and the alkaline mineral filter, which comes standard on every unit we install and puts a small amount of mineral back into the finished water. What each stage does is on the reverse osmosis drinking water page above.

The tank is the part people ask about. It holds 4.8 gallons, and about 2.5 to 3 of those are usable. The tank carries an air charge that pushes the water out to the faucet, and as the tank empties the air expands and the last gallon or two stays behind at low pressure. The moment you draw a pitcher, the membrane starts refilling the tank, so the working supply is a rolling two and a half gallons rather than a fixed one. When the tank is full, an automatic shut-off valve stops production; open the faucet and it starts again.

Why a stored supply is the right build on a well

It is the only reverse osmosis we install on a well; why the tankless unit stays off wells is on that unit’s page. With a tank, the membrane refills in the background and the faucet pours from the reserve, so the membrane is never asked to make a glass of water at the speed you pour one. It can take its time on the heavier dissolved-solids load a well delivers, because the tank, not the membrane, is what answers the faucet. A well running high TDS, or a prefilter partway through its life, slows the refill; you notice it only if the tank runs dry before the membrane catches up, and in a household drinking a few gallons a day it rarely does.

That is the whole argument for storage on a well, and it is a mechanical one rather than a sales one. The reserve is what lets a membrane on well water behave the way a membrane on softened city water does at the tap.

27 gallons on the certificate, 100 on the membrane: both are true

Our tank unit is certified to NSF/ANSI 58 by IAPMO R&T, an accredited certifier that tests to the same standard NSF International does. The listing is file WC-14468, in the category “Systems with Storage Tank and Automatic Shut-off Valve,” and the claim on the certificate is TDS reduction. NSF/ANSI 58 will not certify a reverse osmosis system unless it reduces total dissolved solids by at least 75 percent, so a listing under that standard is a statement about what the unit was measured doing, not a sticker.

The listing records a certified daily production rate of 27.05 gallons per day under the standard’s test conditions; the membrane’s own rating is 100 gallons per day. The two numbers measure different things. The membrane rating is what the membrane element can produce under its maker’s conditions; the certified rate is what the whole assembled system, tank and shut-off valve included, produced when the certifier ran it under the conditions the standard sets. Neither is the number that matters in your kitchen. Most households drink and cook with two to five gallons a day, so either figure is many times what the family will draw, and the storage tank is sized to that daily use, not to the membrane.

Its place in a well build

Grit and iron are what shorten a membrane’s life, so on a well a sediment pre-filter, $500, goes in ahead of it, and the RO is the last piece of the build. How the layered build goes together, and in what order, is on our well water treatment page. Where a well also needs iron or sulfur equipment, we put a number on that after the free water test, not before, because the build depends on what the test shows.

Owning this unit on a well costs less inside the well build than on its own, and that math is in the table below: added to our well dual-tank system, the tank RO is $350 rather than $800.

If nitrate is why you are reading this page, here is what we can and cannot say. EPA lists reverse osmosis among the best available technologies for nitrate in its drinking water regulations, alongside ion exchange and electrodialysis, so a membrane at the kitchen tap is the technology class EPA points to. We do not publish a nitrate removal percentage for our unit, because its certificate is for TDS reduction and we will not claim what has not been tested. Get the county lab number first; our nitrate guide covers what it means.

What $800 buys, and what the well build adds

The first five rows are inside the price. The rest are extra, and each is a fixed number rather than a surprise.

Financing is available at 0% on approved credit through a third-party lender, and military members and first responders take $100 off. The before-and-after water test that backs every install is spelled out on our guarantee page.

Owning it: $199 a year

A tank RO home is $199 a year for our annual visit, which covers all the RO filters, a water test and a full system check. That water test is when the membrane gets checked, so a tank home pays $199 and knows each year where its membrane stands. What goes wrong with an RO and what each fix costs is on our reverse osmosis service page.

When a city kitchen picks the tank

The tank unit is not only a well product. On city water either of our systems works, and a city household picks the tank when it wants a stored supply: the unit runs on household water pressure and needs no powered outlet under the sink, it is the style we run a refrigerator or ice-maker line from where the layout allows, and it pours from the reserve rather than at the membrane’s pace, because the tank is doing the pouring. What it asks in return is cabinet floor space for the tank. The cabinet-space trade is on the tankless page.

Three things the tank asks for, on either supply:

• Cabinet floor space for a 4.8-gallon storage tank beside the filter assembly.
• A drain tie-in under the sink, which the licensed plumbing professional makes on install day.
• No outlet. The tank runs on the pressure already in your cold line.

Size it for your well, or your cabinet

The in-home water test is free and comes with no obligation; on a well, have your county lab results handy if you have them and we will size the build around both. Call or text 319-319-6566, email ryan@kindwaterco.com, or start with our instant quote, which takes about two minutes.