Home Water Treatment

Here’s the thing nobody tells you at the hardware aisle: water treatment isn’t one product. It’s three different jobs, and buying the wrong one wastes money. A softener won’t pull arsenic out of well water. A drinking-water system under the sink won’t protect the pipes in your whole house. Before anyone sells you a tank or a cartridge, the water needs testing — because municipal supply and private well water are completely different animals, and what’s actually in the water dictates the fix.

For broader project planning, explore WBC’s building materials resources.

Start there. A water test pinpoints the issues — staining on appliances, laundry that never comes clean, that off taste — and identifies what’s coming out of the tap. Whether the supply is municipal or well dictates the right fix. Guessing is how people end up with a system that solves a problem they don’t have.

The Three System Types and What Each One Actually Does

These get confused constantly. They are not interchangeable.

Reverse osmosis (under-sink, point-of-use). This is your drinking-water workhorse. A certified RO system reduces over 90 contaminants, including viruses, bacteria, mercury, arsenic, PFAS, lead, and microplastics. The way it works is staged: the core levels of filtration are the sediment/carbon pre-filter, the RO membrane, and a post-filter, which provides protection against a broad array of issues including total dissolved solids, heavy metals, chlorine, and lead. This treats the water you drink and cook with — not the whole house.

Whole-house filtration (point-of-entry). This treats every tap by filtering where water enters the home. The catch is you choose the filter for the specific problem. There are three advanced filter options — the Filtr-Cleer four-in-one filter addresses dirt, silt, and clay while conserving water pressure; the Cullar activated carbon filter solves chlorine taste and odor issues and discoloration; and the Cullneu acidic water neutralizer tackles low-pH water that can damage pipes and fixtures and stain appliances.

That low-pH neutralizer matters here. Acidic well water corrodes plumbing and fixtures over time — a real concern on private wells where the chemistry runs aggressive.

Water softeners. Different job entirely. Water softeners use an ion exchange process to remove hard minerals like calcium and magnesium. Softening is not filtering. An RO system filters impurities like chemicals and lead from drinking water, while a water softener removes hard minerals that cause scale buildup. Each system targets different water quality issues. Hard water is a nuisance problem — scale, dull laundry, scratchy skin. Contaminants are a safety problem. Don’t conflate them.

Sizes, Stages, and the Certifications That Actually Mean Something

This is where you compare specs instead of marketing.

For whole-house filtration, the tank comes in two sizes, and the carbon capacity scales with it:

Spec	9” Tank	10” Tank
Filter tank size	9 in x 48 in	10 in x 54 in
Overall height	54”	60”
Chlorine taste/odor capacity (Cullar)	up to 120,000 gallons	up to 180,000 gallons
Water pressure limits	20–120 psi	20–120 psi
Temperature limits	33°–120° F	33°–120° F

The Cullar filters are tested and certified by WQA against NSF/ANSI Standard 372, CSA B483.1, and NSF/ANSI Standard 42 for chlorine taste and odor reduction up to 120,000 gallons for the 9” filter and 180,000 gallons for the 10” filter.

That temperature floor of 33°F is worth flagging. In cold country, you don’t put a water system in an unheated space and hope. Protected indoor placement — basement, utility room, heated garage — keeps it inside its operating range and out of freeze risk.

For under-sink RO, the customization runs deep. You get up to seven stages of filtration and 14 filter options, certified to reduce over 90 contaminants. There’s a choice of one- or two-year filters.

On certifications — this is the part that separates a real system from a gadget. The Aquasential Smart RO is tested and certified by WQA to NSF/ANSI 58, NSF/ANSI 42, NSF/ANSI 53, NSF/ANSI 401, NSF/ANSI 372, CSA B483.1, and NSF Protocol P231. In plain terms: 58 covers RO performance, 42 covers chlorine taste and odor, 53 covers health-related contaminants, 401 covers emerging contaminants, 372 is lead-free certification, and P231 covers virus and bacteria reduction. If a product can’t show third-party testing to these standards, treat its contaminant claims as marketing.

Well Water Add-Ons and PFAS

Montana runs heavy on private wells, and wells bring their own list — arsenic, iron, sediment, bacteria. The base RO setup handles a lot, but specific well problems call for specific cartridges:

You can enhance the system with add-on options. The Total Defense Cartridge adds filtration for PFAS, pharmaceuticals, mercury, VOCs, and pesticides. The Advanced Post Tank Filter expands protection to address bacteria and viruses and is ideal for well water. The Arsenic Filter reduces arsenic where that issue is significant. And the Mineral Boost Cartridge adds natural calcium minerals back into the water for pH-balanced taste.

PFAS deserves a note. The EPA recently updated PFAS regulations — which is exactly why a PFAS-rated stage is worth asking about, especially if a test flags it.

On the parts side, replacement cartridges come in several configurations — sediment-style P5 cartridges, the RFCBBS and CWF filter cartridges, the SCWH-5 advanced filter cartridge, and the HF360A whole-house filter housing among them. If you’re testing for lead first, DIY lead surface test kits exist for a quick check before committing to a system.

Installation: Know This Before You Buy

The install requirements decide where the system can go — and getting it wrong can void the warranty.

For whole-house: you need access to the main water piping, a drain, and an electrical outlet. Models can be placed in basements, laundry rooms, garages, or outdoors. Outdoor installations must use specific outdoor-rated power supplies.

For under-sink RO: you need a cold water line and a drain. These systems can go under the sink, in the basement, garage, crawlspace, or other areas — anywhere in the home with access to a cold water line.

One hard rule worth respecting: improper installation by untrained persons voids the warranty and may cause damage. A water system tied into your supply line and a drain isn’t the place to wing it.

Frequently Asked Questions

What’s the difference between filtering water and softening it? Filtering water separates impurities like minerals, particulates, iron, hydrogen sulfide, or organic matter by passing water through a filter bed that traps impurities. Softening water uses an ion exchange process that removes dissolved solids like magnesium and calcium. Filtering targets contaminants and taste; softening targets hardness and scale.

Do I need a whole-house system or just an under-sink one? Depends on the problem. If the issue is drinking and cooking water quality, an under-sink RO handles it. If the problem impacts the entire home — sediment, acidity, or chlorine across every tap — that’s what whole-house filtration addresses. A water test tells you which.

How long do the filters last? For RO drinking systems, there’s a choice of one- or two-year filters. Whole-house carbon capacity is rated by volume — up to 120,000 gallons for the 9” filter and 180,000 gallons for the 10” filter for chlorine taste and odor reduction.

What contaminants does reverse osmosis actually remove? A certified RO system reduces over 90 contaminants, including viruses, bacteria, mercury, arsenic, PFAS, lead, and microplastics. The specific list depends on which of the staged filter options are configured.

Can I install one in an unheated garage or outdoors? Placement is flexible, but watch temperature. Whole-house filters operate between 33° and 120° F. Outdoor placement is possible but requires outdoor-rated power supplies. In cold climates, a heated indoor space is the safer call.

Why start with a water test instead of just buying a system? Because the right system depends on what’s actually in the water — and well water differs from municipal supply. A test of your tap water shows what you’re dealing with, so the system matches the real problem instead of a guess.