Viomi V8 PRO vs Waterdrop G3P800: Matching 800 GPD Ratings, Different Cartridges and Extras

The rating and the ratio are where the Viomi V8 PRO and the Waterdrop G3P800 match, since each is a tankless under-sink RO system rated at 800 GPD with a 3:1 pure-to-drain ratio. For a household that wants a compact main unit, two cartridges to keep up with and filter reminders on a phone, the Viomi V8 PRO is the better fit.

The G3P800 brings extras of its own. Its base kit packs a UV sterilizer between the system and the faucet, it runs on three cartridges, and its main unit carries a front-panel screen.

The Two Configurations Being Compared

Out of the box, the Viomi V8 PRO is ready with its RO800 membrane and one PCB composite cartridge already in place, and a second PCB waits in the box for the first scheduled change. The smart faucet and the installation parts come with it, so the system arrives ready to go under a kitchen sink.

Waterdrop sells the G3P800 in more than one kit. The base model compared here, WD-G3P800-W-FC, arrives with three cartridges (CF, CB and RO, each sold by Waterdrop as its own replacement part: WD-G3-N1CF, WD-G3-N3CB and WD-G3P800-N2RO), a smart digital RO faucet and a preinstalled UV sterilizer. For households that want minerals added to the RO water, Waterdrop also lists the same system with an external MNR35 remineralization filter (WD-G3P800-W-MZ) or an ALK35 alkaline filter (WD-G3P800-W-ALK). The MNR35 is an independent filter with 1/4 inch quick-connect fittings, rated for 12 months, and Waterdrop rates the ALK35 for 6 months and describes it as raising pH to 7.5 to 9.5.

Matching Specs and the Ones That Differ

The specs the two systems share:

And the specs that differ:

The first table is a match line for line. The 800 GPD figure is a membrane rating on the Viomi V8 PRO, and Waterdrop's manual gives its 800 GPD as a maximum daily production rate measured at 30 psi of dynamic feed pressure and 77°F. With a nominal 3:1 ratio on each, both are rated to send one part of water to the drain for every three parts of purified water, and each is a tankless design with a built-in pump.

Where they part ways is in stage counts of 9 and 10, in the cartridge layout and in the size of the box under the sink, and the last two shape what ownership looks like day to day.

The UV Sterilizer in the G3P800 Box

The feature that sets the G3P800 apart is the UV sterilizer that ships with its base kit. Waterdrop preinstalls it in the purified-water line between the system's outlet and the faucet, and the main unit powers it. Its manual explains that the UV stage only switches on when the faucet is opened and water flows past it. Because it sits in the line to the faucet, it acts on the water the household draws there for drinking and cooking. Waterdrop says the unit reduces up to 99.9% of bacteria and that its LED part has a long lifespan with little to no maintenance.

For a household that wants a UV step after reverse osmosis and prefers to have it arrive with the system, the G3P800 includes that component in its standard kit.

Cartridges and the Spare PCB Over a Two-Year Cycle

The Viomi V8 PRO's two cartridges set a simple rhythm. The PCB composite cartridge is rated for 12 months and the RO800 membrane for 24 months, and the faucet and the app follow the remaining life of each. When a change approaches, the control-panel lights turn orange 10 to 15 days ahead and the app adds a replacement reminder of its own. The first PCB replacement is already in the box, so under normal household use the box contents cover up to two years without buying another pre-filter. Each cartridge is a tool-free twist and pull, and between changes the Viomi V8 PRO flushes itself every 12 hours, opening the inlet valve for 70 seconds without running the pump.

The G3P800 splits the work across three cartridges. Waterdrop describes the first as a pre-sediment and carbon block filter (CF), the second as the RO membrane, and the third as a coconut carbon block post-filter (CB) that the water passes through after the membrane, and it rates the CF for up to 6 months, the RO for up to 24 months and the CB for up to 12 months. Both RO membranes carry the same 24-month rating.

Measured against those rated lives, the Viomi V8 PRO's two-cartridge layout works out to three replacement cartridges over two years, counting the changes due at month 24, one of them the spare in the box, while the G3P800's three-cartridge layout works out to seven. Our filter life replacement planner shows how cartridge ratings translate into a household plan.

Faucet Screens, the Front Panel and the Viomi App

Both faucets show the same two things, a TDS reading and filter life, so the daily glance at the counter works alike on either system. TDS gives an overall picture of dissolved solids, which makes the faucet number a handy everyday reference. On the Viomi V8 PRO, the faucet is wired to the main unit through a signal cable, so the numbers on the counter come straight from the system below. The difference is where else that information goes.

The G3P800 repeats it on a screen on the front of the main unit, which shows the TDS reading along with CF, CB and RO filter indicators and puts the same information in front of anyone working in the cabinet, such as during a cartridge change. Waterdrop's manual also describes the faucet screen marking the three cartridges by color. Waterdrop also describes a quantitative water intake function on its smart faucet, so a set amount can be dispensed without standing at the tap.

The Viomi V8 PRO extends the same readings to the Viomi app, which shows TDS before and after filtration, keeps a water usage report, tracks filter life and pushes a replacement reminder. That keeps whoever orders cartridges informed through the app.

Cabinet Footprint and Hookups

With the main unit under the sink and only the faucet on the counter, the cabinet itself is the main thing to plan around for either system. The Viomi V8 PRO's main unit measures 16.3 inches long, 5 inches wide and 12.8 inches high. The G3P800 measures about 18.1 by 5.7 by 17.7 inches. At 5 inches wide, the Viomi V8 PRO's main unit suits cabinets where it shares space with cleaning supplies. On those figures the Viomi V8 PRO is shorter, narrower and lower, with the height gap the largest at roughly five inches, which is worth setting against any shelf or drain trap in the cabinet. Our roundup of compact reverse osmosis systems covers more units sized for tight cabinets.

Both follow the familiar under-sink RO layout, with the main unit in the cabinet, a connection to the standard cold-water supply and drain, and the display faucet on the counter; for the G3P800, Waterdrop notes that an existing soap-dispenser hole can hold the faucet. Installation parts are in the Viomi box, and a step-by-step installation video walks through the setup.

The Viomi V8 PRO can also feed a compatible refrigerator or ice maker using standard tubing and the tee fitting supplied with the system. Our guide to connecting an RO system to a refrigerator goes through that hookup.

How the Two 800 GPD Systems Sort Out

With the same rated output and nominal ratio, the choice follows the extras each household cares about. A UV stage that arrives in the base kit is the clearest reason to pick the Waterdrop G3P800. Readings on the main unit as well as the faucet, and a faucet that dispenses a set amount, add to its appeal, provided the cabinet has room for its taller box.

Minerals are a separate question, and each brand answers it with a different product. Waterdrop covers it with its MNR35 and ALK35 kits, and within Viomi's range the Viomi M1 builds remineralization into a single unit.

Tight under-sink space points to the Viomi V8 PRO, along with an easy upkeep plan: two cartridges, a spare already in the box, and tracking on the faucet, the panel and the app. Its refrigerator and ice maker connection adds one more use for the purified water.

FAQ

What does the extra PCB filter in the Viomi V8 PRO box mean?

The box holds one RO800 cartridge and two PCB composite cartridges, with one PCB installed and the other packed as a spare. The spare is the same PCB composite cartridge as the one already fitted, ready to go straight in when the faucet and the orange panel lights signal that the first change is near. Under normal household use, that means up to two years of ownership without buying another pre-filter.

What does the UV stage on the G3P800 add?

It adds a final treatment step after the RO membrane, at the point where water leaves the system on its way to the faucet. On the G3P800 it comes in the base kit, draws its power from the main unit and switches on only while water flows.

Which of the two takes less room under the sink?

The Viomi V8 PRO's main unit measures 16.3 × 5 × 12.8 inches, smaller in all three directions than the G3P800 at about 18.1 × 5.7 × 17.7 inches. The largest gap is in height, at roughly five inches.

What faucet comes with each system?

Each system ships with a smart faucet that carries its readings. The Viomi V8 PRO's faucet connects to the main unit through a signal cable and displays TDS and filter life, right where the water is poured. The G3P800 arrives with Waterdrop's smart digital RO faucet, a non-air-gap design that shows TDS and filter life on its own screen.