What Is the Best Whole House Water Filtration System?

Every brand, including ours, would like you to believe its system is the best whole house water filter. The honest answer is that "best" depends on three things: what is in your water, how much water your home uses at once, and how much upkeep you are willing to do. Get those three right and the choice narrows to one or two systems. Get them wrong and even an expensive system disappoints.

This guide walks through the decision in the order we use with customers on the phone. It names competing products and links to their published specifications, because a comparison that only mentions one brand is an advertisement.

Step 1: Find out what you are filtering

A whole house filter treats every drop entering the home, so it has to be matched to the water that actually arrives at your meter or well. Two sources will tell you most of what you need.

• City water: your utility publishes an annual water quality report, and the EWG Tap Water Database summarizes it by zip code. City water is disinfected, so chlorine or chloramine, their by-products, taste and odor are the usual concerns.
• Well water: nobody tests it for you. A laboratory water test is the first purchase, not the filter. Iron, hydrogen sulfide (the rotten-egg smell), hardness, sediment and bacteria each need different treatment, and a filter sized for the wrong problem will clog or simply pass the contaminant through.

If you cannot see, smell or taste a problem, that does not mean there is none. Lead, arsenic and most chemical contaminants are invisible. The contaminants library explains what each one is and what removes it.

Step 2: Choose the type of system

Whole house filters fall into four families. They are not interchangeable, and the right family is a bigger decision than the brand.

Single cartridge housing

A housing on the main line with one replaceable cartridge, usually for sediment. Culligan's WH-HD200-C is a typical example. Inexpensive and simple, and if your only problem is grit, it may be all you need. It does not address chlorine, metals or chemicals on its own.

Multi-stage cartridge system

Two or three housings in a row, typically sediment, KDF and carbon block. Express Water's WH300SCKS is the common reference. Broader treatment than a single housing, with cartridges that need replacing on a schedule the manufacturer publishes as up to 100,000 gallons or 6 to 12 months. Budget for those cartridges over the life of the system.

Carbon tank system

A large tank of carbon media with a sediment pre-filter and sometimes a post-filter. Aquasana's Rhino WH-1000 is the best-known. Long main-tank capacity (Aquasana publishes 1,000,000 gallons or 10 years) with smaller pre- and post-filters that still need changing. Carbon is excellent on chlorine, taste and odor; on its own it is not an iron, sulfide or hardness solution.

Backwashing multi-media tank

A tank holding several media layers with a control valve that periodically backwashes the bed to clean it. The AquaOx and Crystal Quest's SMART series are in this family. No cartridges to change; the trade-off is that the system needs a drain and power for the valve, and the media is eventually replaced rather than swapped monthly. This is the family to look at when you want one system to handle several concerns at once, or when you are on a well with a known problem.

Step 3: Compare on the five things that matter

Once you know the family, compare specific models on these points. Our comparison page lays them side by side for the models above, with each manufacturer's published figures and the date we checked them.

1. Documented contaminant reduction. A media ingredient or a "removes 300 contaminants" headline is not test data. Ask which exact model was tested, for which contaminant, at what concentrations and flow. Our performance page lists the questions to bring to any manufacturer, including us.
2. Rated flow, not peak flow. Peak flow is the most water a system can pass. Rated or service flow is the rate at which it still treats water properly. Size to the fixtures that run at the same time: two showers, a washer and a kitchen tap is a different demand than one shower. The flow and pressure guide shows how to count.
3. Capacity and upkeep. Cartridge systems cost less up front and more over time; tank systems reverse that. Build the estimate with the ownership cost tool or the cost guide.
4. Warranty terms. Read what is actually covered. Published warranties in this category run from 1 year (Express Water) to 10 years (Aquasana's limited warranty; AquaOx's tank and control valve coverage). Media and cartridges are consumables and are generally not covered by anyone.
5. Installation requirements. Space, drain access, power and pipe size. A backwashing tank needs a drain; a cartridge system needs room to open the housings. Check the installation requirements before you buy, not after.

Which AquaOx is right for you

If the multi-media family is the right fit, we make three systems, and we would rather sell you the right one than the biggest one.

• Carbon by AquaOx: city water, homes up to about 3 bathrooms, when chlorine, taste and odor are the concern. Carbon-only media, 5-year warranty.
• The AquaOx: our flagship multi-media bed. City or well water (with pretreatment matched to your test), homes up to about 4 bathrooms, 15 GPM peak flow, 10-year tank and control valve warranty.
• The AquaOx XL: the same media in a larger bed for homes with 5 or more bathrooms or high simultaneous demand, 37 GPM peak flow.

Current pricing and the full side-by-side are on the whole house water filters page, or take the two-minute system finder and we will narrow it for you.

When a whole house filter is the wrong answer

Some problems need a different product, and no filter in any of the four families above fixes them.

• Hard water (scale, spotted dishes, dry skin) is calcium and magnesium. That is a water softener job. A filter and a softener are often installed together, but one does not replace the other.
• Drinking water only. If you want the purest possible water at the kitchen tap and are not worried about showers and laundry, an under-sink reverse osmosis unit costs a fraction of a whole house system.
• Bacteria in a well. Filtration is not disinfection. Start with shock chlorination and a retest, then add UV or filtration for ongoing protection.

The worth-it guide goes deeper on when whole house filtration pays off and when it does not.

A checklist before you buy

• I know what is in my water, from a utility report or a lab test.
• I know which system family treats those contaminants.
• I have seen test data for the exact model, not just the media.
• The rated flow covers my peak simultaneous demand.
• I have a 10-year cost estimate that includes cartridges or media.
• I have read the warranty terms, including what is excluded.
• I have checked the installation requirements against my mechanical room.

If you can tick all seven, you have found the best whole house water filtration system for your home. If you are stuck on any of them, send us your water report and we will go through it with you.