Under-sink filters protect your drinking water. Whole house systems protect every tap, every shower, every appliance. The right answer depends on what's in your water and how your family uses it.
The question is not which system is better — it is which problem you are trying to solve.
An under-sink filter is a point-of-use system. It treats water at a single tap — typically your kitchen sink — and provides the highest possible purity for the water you drink and cook with. It does not treat the water in your showers, your laundry, your dishwasher, or any other fixture in your home.
A whole house filter is a point-of-entry system. It treats all water entering your home before it reaches any fixture, providing a baseline level of protection at every tap, every shower, every appliance. It typically cannot achieve the same depth of treatment as a dedicated under-sink RO system — but it protects exposure pathways that an under-sink filter simply cannot reach.
Under-Sink Filter
Highest purity for drinking water
Removes PFAS, heavy metals, fluoride, nitrates
RO achieves 95–99% TDS removal
Remineralization restores pH and taste
Compact — installs under one sink
Lower upfront cost
Does not treat shower water
Does not protect appliances
Does not address dermal/inhalation exposure
Whole House Filter
Protects every tap, shower, and appliance
Addresses dermal and inhalation exposure
Removes chlorine, chloramines, sediment
Protects water heater and pipes from scale
Single point of maintenance for whole home
Extends appliance lifespan
Cannot match RO purity for drinking water
Higher upfront cost and installation complexity
Requires adequate space (garage, utility room)
The distinction between whole house and under-sink is not just about coverage — it is about the chemistry each system is designed to address. AION engineers both systems around the specific contaminants each exposure pathway presents.
AION Whole House
AION CORE
Catalytic carbon foundation — destroys chloramines, chlorine, VOCs, THMs at the point of entry. Vortech distribution plate prevents media channeling.
AION PFAS
MOF/COF adsorption media — 6,000+ m²/g surface area, 5× standard carbon. Captures all 6 PFAS families including GenX.
AION REDOX
+950 mV ORP electrochemical stage — destroys bacteria, viruses, lead, glyphosate, chromium-6, and microplastics without chemicals.
AION SALT-FREE
Nucleation Assisted Crystallization — converts hardness to harmless micro-crystals. No salt, no sodium, 5–7 yr media life.
AION Under Sink — 7-Stage
Sediment Pre-Filter
5–10 micron polypropylene — captures sand, rust, and suspended solids before they reach the RO membrane.
Centaur® Catalytic Carbon
Destroys chloramines, VOCs, and PFAS precursors. Standard carbon cannot break the chloramine bond.
Nano-Ceramic Membrane
0.001–0.01 micron — removes bacteria, viruses, cysts. Backwashable, rated 5–10+ years. Extends RO life 2–5×.
RO + DI + UV + Remineralization
95–99% rejection of PFAS, heavy metals, fluoride, nitrates. DI polishes to <5 TDS. UV final microbial kill. Natural calcite restores pH 7–8.5.
Most people think about water quality exclusively in terms of what they drink. But your skin is your largest organ, and hot showers open pores and create steam — both of which increase the absorption and inhalation of whatever is in your water.
Chlorine and chloramines — the disinfectants used in virtually all municipal water supplies — are volatile compounds. When you take a hot shower, you are inhaling chlorine vapor and absorbing chloramines through your skin. Research has shown that for some individuals, this exposure pathway can be comparable to or exceed the exposure from drinking water. An under-sink filter does not address this. A whole house system does.
Unfiltered water carries sediment, scale-forming minerals, and chlorine that degrade appliances over time. Water heaters, dishwashers, washing machines, and ice makers all experience accelerated wear when operating on hard, chlorinated, or sediment-laden water. A whole house system installed at the point of entry removes sediment and conditions water before it reaches any appliance — extending service life and reducing maintenance costs.
Scenario
Your primary concern is drinking water quality — PFAS, lead, fluoride, nitrates
An under-sink multi-stage RO system provides the highest purity for drinking and cooking water at a lower cost than a whole house system.
Scenario
You have chloramine in your municipal water and are concerned about shower exposure
Catalytic carbon at the point of entry removes chloramines from all water entering the home, addressing both drinking and shower exposure.
Scenario
You have well water with unknown contaminants
Well water can contain a wide range of contaminants. A certified laboratory test is essential before selecting a system. Most well water scenarios benefit from both whole-house treatment and a dedicated under-sink system for drinking water.
Scenario
You want comprehensive protection across all exposure pathways
A whole house system provides baseline protection at every point of use. An under-sink RO system provides the highest purity for drinking water. Together, they address every meaningful exposure pathway.
AION Water — Both Systems
The AION Whole House system starts with AION CORE (catalytic carbon) and adds precision treatment stages — AION PFAS (MOF/COF, 6,000+ m²/g), AION REDOX (+950 mV electrochemical), and AION SALT-FREE (NAC scale prevention) — in dedicated Vortech pressure vessels engineered for the contact time each chemistry requires.
The AION Under Sink 7-Stage system adds Centaur® catalytic carbon, nano-ceramic membrane, high-rejection RO, mixed-bed DI, NSF/ANSI 55 UV, and natural calcite remineralization at your kitchen tap — providing laboratory-grade purity for drinking and cooking water.
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