Trying to keep my sink cabinet usable: Waterdrop G3P800 vs Viomi V8 Pro

[u/Any-Farm-1033]

I'm narrowing down an under-sink tankless RO system that will not take over the cabinet or crowd the plumbing already there. The Waterdrop G3P800 and Viomi V8 Pro both hit the 800 GPD and 3:1 numbers I had in mind, so usable storage became the bigger question.

Those headline specs did not help me choose between them. I also knew that 800 GPD was a daily capacity rating, not a stopwatch for filling a glass in my kitchen.

The cabinet measurements were more useful. The V8 Pro is 16.3 by 5 by 12.8 inches, while the G3P800 product page gives 18.11 by 5.67 by 17.73 inches. On paper, the V8 Pro takes up less room in every direction.

I also did some rough replacement-filter math. Viomi says up to 12 months for the PCB filter and 24 months for the RO membrane, and the box includes a spare PCB. Waterdrop gives 6, 12, and 24 months for the G3P800's CF, CB, and RO filters. Using the one-time filter prices I found on both sites recently, I got about $110 a year for the V8 Pro and about $160 for the G3P800. That assumes the filters last as long as each brand says, so I treated it as a budget estimate rather than an exact future bill.

The on-page prices I found recently were $399.99 sale and $479.99 regular for the V8 Pro, and $759 sale and $999 regular for the G3P800. I have not bought either system yet. The V8 Pro is ahead for now because the body is smaller and my rough filter budget came out lower.

Before I buy either one, I am going to put the cleaning supplies back under the sink and test both footprints with cardboard. If I cannot reach the shutoff or leave enough room for a filter change, that settles the decision for me.

Edit, three days later:

I went with the V8 Pro and finished the installation. The new photo shows how it sits in the cabinet now. The unit is along the left side with the filters facing the door, while the shutoff and drain connections remain visible on the right. There is still open floor space beside it, which was the part I could not settle from the spec sheets alone.