How to Choose an Under-Sink Water Filter Brand for Your Home

A home on city water whose main complaint is chlorine taste or odor is well served by an under-sink carbon filter such as the Viomi Under-Sink Carbon Filter, which adds a separate drinking faucet and needs no power or drain. A home that also wants dissolved solids reduced, and has an outlet and a drain line under the sink, is shopping for reverse osmosis (RO), and the Viomi V6 PRO fits that kitchen: it is a 600 GPD tankless system whose LCD smart faucet shows purified-water TDS and filter life.

The brand question gets easier once those two facts about your home are settled. Viomi makes both kinds of under-sink system, from carbon filters to tankless RO with remineralization, and specific models from Aquasana, Waterdrop, iSpring and APEC come up in the same comparisons, each with its own connection or cartridge format.

Your Water Report Decides Carbon or RO

Your utility's annual water quality report, or a lab test if you're on a well, tells you which technology the job calls for.

• Taste and odor, mostly chlorine. Activated carbon is the tool, and an under-sink carbon filter is all the hardware needed.
• Dissolved solids, or a salty or mineral taste. EPA notes that reverse osmosis is effective for removing chloride, total dissolved solids and other inorganic substances, which is the work carbon alone isn't designed for.
• One specific substance named in the report. Compare models on evidence that names that substance for that exact model, whether it's a certification listing or a published lab test.

A useful habit while reading the report: note the disinfectant line (chlorine or chloramine) and any total dissolved solids figure, since those two lines speak directly to the carbon-or-RO choice. Our guide to TDS explains how to read that number.

Measuring the Cabinet, Plus Room for Cartridge Changes

The footprint printed on the box is only part of the space a system takes. Cartridges have to come out, hoses need slack, and connectors need clearance above or behind the unit. For the Viomi M1, Viomi V6 PRO, Viomi V8 PRO and Viomi B6W, plan an under-sink space of 20.0" × 12.0" × 20.0", and the figures below show what each unit occupies and what extra room to leave.

Measure width, depth and height at the narrowest point, which is usually where the drain trap or a garbage disposal sits, and plan around that recommended space. Within that space, the slim 5-inch body of the Viomi V6 PRO and Viomi V8 PRO leaves more room beside a disposal than a wider unit would. Tank-style RO systems such as the iSpring RCC7 and APEC ROES-50 also need room for the storage tank (3.2 gallons on the iSpring RCC7), so include the tank in your measurements if you compare them.

How an Under-Sink Filter Connects to Your Sink

Through the faucet you already have. A direct-connect carbon filter sits on the cold-water line and sends filtered water out of the existing kitchen faucet. The Viomi Under-Sink Water Filtration System (VM-IUO1PCW-L-US) works this way, with 3/8" direct-connect hoses and a 3/8" to 1/2" adapter included. The Aquasana Claryum Direct Connect (AQ-MF-1) and Waterdrop 15UA take the same approach. Nothing is drilled in the counter, and the Viomi and Waterdrop models run without electricity.

Through a separate drinking faucet. The Viomi Under-Sink Carbon Filter comes with its own faucet and connects to the cold supply with an included three-way ball valve. It needs one faucet hole in the counter or sink deck, but no electricity and no drain connection, and the main faucet stays unfiltered for washing up.

Through an RO faucet with a drain line. An RO system sends a share of water to the drain, so it needs a drain connection as well as a faucet hole. For the Viomi M1, Viomi V6 PRO, Viomi V8 PRO and Viomi B6W that means a 1" to 1.5" hole for the faucet and a 1/4" hole in the drain pipe, plus a standard outlet that stays powered. If the sink has a garbage disposal on a wall switch, give the RO its own always-on outlet, on a GFCI-protected circuit. The faucet, fittings and tubing for installing the system come in the box, and each model has a step-by-step installation video. These Viomi RO systems are designed for municipal tap water.

On inlet pressure, the Viomi V6 PRO, Viomi V8 PRO, Viomi B6W and Viomi M1 all work from as low as 14.5 psi.

Viomi Under-Sink Lineup Matched to Household Needs

Every RO model in the table can also run a separate line to a compatible refrigerator or ice maker through standard tubing, which matters if you want filtered ice without a second system. The Viomi M1 sets this up through "Multi-device Mode" in its app. For lead-free materials, Intertek has authorized the NSF/ANSI/CAN 372 mark for the Viomi V6 PRO, Viomi V8 PRO, Viomi B6W and both under-sink carbon models, and the Viomi M1 was tested by SGS for lead reduction above 99.87%.

Upkeep and Getting Replacement Cartridges

For under-sink systems, the practical upkeep questions are how often a cartridge change comes around and where the cartridge comes from. Viomi offers dedicated replacement cartridges, such as the PCB filter for the Viomi V6 PRO and Viomi V8 PRO, made to fit those two systems.

On the RO models, the systems themselves flag when a change is coming. The Viomi V6 PRO and Viomi V8 PRO show filter life on the faucet and light the control panel orange 10 to 15 days before a change is due. The Viomi M1 shows the PCB and RO balance as a percentage on its faucet screen, and its app shows filter usage and days left. The Viomi B6W lights its PPC and RO indicators on the unit.

Aquasana takes a similar approach: its SmartFlow RO uses twist-out replacement cartridges specific to that system, and the Aquasana Claryum Direct Connect runs 784 gallons or up to six months per cartridge. Using the cartridge made for your exact model, such as Viomi's dedicated replacements, keeps the system working as designed.

Example Picks for Different Household Setups

These example households show how the choices above come together in different kitchens.

A city apartment where only the chlorine taste bothers anyone. The kitchen has a pull-down faucet and no spare countertop hole. The Viomi Under-Sink Water Filtration System (VM-IUO1PCW-L-US) connects to the cold line and filters the water coming out of that same faucet, and one cartridge lasts up to 12 months.

A family of four that wants RO water and filtered ice. They cook with filtered water every day and want the refrigerator line on the same system. The Viomi V8 PRO's 800 GPD rating and spare PCB in the box suit heavier daily use, and a standard tubing run reaches the fridge.

A crowded cabinet with a garbage disposal and a dishwasher supply line. Width is the constraint. When the measured width, depth and height leave room for the unit, its connections and cartridge access, the 5-inch-wide Viomi V6 PRO, or the 5.91-inch-wide Viomi B6W if they'd like to use a compatible faucet of their own, can sit beside the disposal, with a separate always-on outlet added for the RO.

FAQ

Which lines in my water report decide carbon versus RO?

Look at the two lines in your water report that speak to this choice: the disinfectant and total dissolved solids. If chlorine taste is the complaint and dissolved solids don't concern you, carbon is enough. If you want dissolved solids reduced too, or the report shows a substance that a specific RO model has evidence for, choose RO.

Does every under-sink filter need a new faucet hole?

No. Direct-connect carbon filters such as the Viomi Under-Sink Water Filtration System (VM-IUO1PCW-L-US) feed your existing faucet. Carbon filters with a dedicated tap need one faucet hole, and RO systems need a faucet hole plus a drain connection; for the Viomi RO models that's a 1" to 1.5" faucet hole and a 1/4" drain hole. Many sinks have a spare knockout or sprayer hole that can take the faucet.

How much space should I leave for changing cartridges?

For the wall-mounted Viomi carbon filters, keep at least 60 mm (about 2.4 inches) under the housing. For Viomi RO systems, plan a 20.0" × 12.0" × 20.0" space, and keep the 2.0 to 3.9 inches behind the Viomi M1, or the 1 to 1.5 inches above the Viomi B6W, free for tubing and connectors.

Can the filter share the cabinet with a garbage disposal or dishwasher line?

Usually, yes, as long as the measurements work. The practical points are power and access: a powered RO system such as the Viomi models needs an always-on outlet rather than the disposal's switched one, and the cartridges should stay reachable without unhooking the dishwasher supply.

Measuring List for Your Sink Cabinet

1. Measure the cabinet's inside width, depth and height at the narrowest point, around the drain trap or disposal.
2. Photograph the cold-water valve and the faucet supply hose so you know whether you're working with 3/8" or 1/2" connections.
3. Check whether the outlet under the sink is controlled by a wall switch, and note whether a second, always-on outlet is nearby.
4. Look at the sink deck and counter for a spare hole or knockout that a drinking faucet could use.
5. Find the drain tailpiece below the sink and make sure there's room above the trap to attach a drain line.