Best Under-Sink Reverse Osmosis Filter 2026 — Tankless vs Tank Comparison

Published 2026-04-25 · Updated 2026-04-25 · 6 min read · By Zomg The Handyman

800 GPD Tankless Reverse Osmosis System - Waterdrop G3P800 · Waterdrop

TL;DR

Tankless RO eliminates the cabinet-eating storage tank and tastes better. Top pick plus install pricing.

Affiliate disclosure: As an Amazon Associate, Zomg The Handyman earns from qualifying purchases. Picks based on what we install on the job — commission does not change your price.

Old reverse osmosis systems had a 4-gallon storage tank under the sink that ate cabinet space and made water taste flat. Tankless RO flows on demand, takes 1/3 the cabinet space, and tastes way better.

Quick Comparison

Pick	Best For	Approx Price
#1 Pick	Waterdrop G3 P800 Tankless Reverse Osmosis	$500-$700

Our Picks

#1 Pick

Recommended on Amazon

Waterdrop G3 P800 Tankless Reverse Osmosis

800 GPD tankless RO. No storage tank wasted under-sink space. Smart faucet.

$500-$700 View on Amazon → Buy direct from Waterdrop →

Partner pick: Waterdrop

Tankless reverse osmosis systems, under-sink filters and softeners direct from the maker.

Deal: Rotating discounts on RO systems and filters on the Waterdrop deals page. Shop the deal →

Buy direct from Waterdrop → All partner deals →

Zomg The Handyman is a partner of Waterdrop through impact.com and may earn a commission on purchases made through these links. It does not change your price.

Why Tankless Beats Tank

Tank RO: water sits 6-12 hours, picks up plastic taste. Tankless: water flows on demand, fresh-tasting every time.

Pure-to-Drain Ratio

Old RO: 1 gallon clean per 4 gallons wasted (1:4). {inline(P['waterdrop_g3'], 'Waterdrop G3 P800')}: 3 clean per 1 wasted (3:1). Saves water bill.

Installation

Under-sink RO install: $129-$249. Most takes 90-120 minutes. We drill faucet hole if your sink doesn't have one.

Need help installing what you bought? Book installation directly or request a free quote. Same-day available across California.

Frequently Asked Questions

Tank or tankless RO?

Tankless. Better taste, less cabinet space, better water efficiency.

How much for installation?

$129-$249 depending on whether your sink needs a faucet hole drilled.

Filter replacement?

Annual change — about $80-$120 in filters. We offer service calls at $49-$79.

Need a Pro in California?

Insured, background-checked handymen. 4.9☆ rated. Same-day available.

Book Online Now →

Outside California?

Zomg only works in California. Duurs, our nationwide sister marketplace, books the same kind of background-checked pros for plumbing anywhere in the US: upfront prices, same-day slots, and a rating you can check first.

Book plumbing on Duurs → See every service →