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Our under-sink reverse osmosis pick

Waterdrop G3P600

G3P600 Black Faucet / WD-G3P600-Black

$539US price, checked Oct 13, 2026

Fast tankless RO with a TDS faucet, but its certification claims are unconfirmed

Check price at Waterdrop Full review →

Under sink reverse osmosis

APEC ROES-50

ROES-50 Essence 5-stage, 50 GPD

$230.99US price, checked Oct 13, 2026

Cheap tank RO with low filter costs and output that depends on your water pressure

Check price at APEC Full review →

Criterion	Waterdrop G3P600	APEC ROES-50
US price	$539Checked Oct 13, 2026 · Price details in the review	$230.99Checked Oct 13, 2026 · Price details in the review
Three-year ownership estimate	$973.91 Incomplete known subtotal. Not included: installation, energy use.	$395.90 Incomplete known subtotal. Not included: installation.
Choose if	A kitchen on city water with a drain and an outlet under the sink, if you want fast RO water without a tank.	You want RO water at one kitchen sink for little money, and your water pressure is near 60 psi.
Main trade-off	No certifier listing was found for the contaminant claims, the warranty is one year, and the power draw isn't published.	Output falls to 30 GPD at 50 psi, and APEC's contaminant claims aren't backed by a confirmed certifier listing.
Key specifications	Rated output: 600 GPD, and Waterdrop says it fills an 8 oz cup in 8 seconds Pure-to-drain ratio: 2:1 Filters: 8-stage. Three replacement filters: G3-N1CF (6 months or 550 gal), G3-N3CB (12 months or 1,100 gal), G3P600-RO (24 months or 2,200 gal) Certification: Waterdrop lists NSF/ANSI 42, 58 and 372. NSF has no G3P600 listing, and IAPMO's directory couldn't be checked Power: Needs an outlet. Power adapter included, wattage not published Water limits: Municipal water, 14.5 to 87 psi, 41°F to 100°F, pH 6.5 to 8.5, TDS under 750 ppm, hardness under 7 gpg (from the extended-warranty terms) Size and weight: 18.11 × 5.67 × 17.73 in, 32.4 lb	Rated output: 50 GPD at 60 psi and 77°F (about 1.8 gal an hour); 30 GPD at 50 psi Drain water: Not published for the ROES-50; APEC's FAQ gives about 3:1 for under-sink systems in general Tank: 4 gal total volume (bladder and air space); about 3.2 gal bladder capacity at 80 to 90 psi; refills in 1.7 to 3 hours (FAQ) or 2 to 3 hours (manual) Filter life: Pre-filters every 6 to 12 months; membrane and stage 5 every 2 to 4 years (the manual says 2 to 3) Feed water limits: 40 to 85 psi; 40 to 100°F; up to 2,000 ppm TDS; pH 2 to 11 Certification: APEC claims WQA certification for TDS reduction; no NSF listing; WQA listing not confirmed Power: None; the manual describes a non-pumped system
Exact variant	G3P600 Black Faucet / WD-G3P600-Black	ROES-50 Essence 5-stage, 50 GPD
Dimensions	18.11 × 5.67 × 17.73 in and 32.4 lb, per the product page's spec table. Waterdrop doesn't say which figure is width, depth or height, or how much clearance you need to swap filters.	System 15.5 in L × 5.25 in W × 17 in H. Tank 11 × 11 × 15 in. Package weight 26 lb. The manual says to allow about 17 × 6 × 18 in for the system and 11 in across and 18 in tall for the tank.
Installation	It goes under the sink and needs a cold-water supply, a drain and an outlet. The kit includes the faucet, a 3/8 in to 1/2 in feed water adapter, a 1/4 in drain saddle, 3/8 in and 1/4 in tubing, lock clips, Teflon tape and a power adapter. Waterdrop says installation takes about 30 minutes and doesn't need a plumber. The product page doesn't give the faucet-hole size or any water limits. Waterdrop's extended-warranty terms do. They call for municipal tap water at 14.5 to 87 psi. Inlet water should be 41°F to 100°F, with a pH of 6.5 to 8.5. TDS must be under 750 ppm and hardness under 7 grains per gallon. Well water needs pre-filtration. It's for indoor use only.	APEC sells it as a do-it-yourself install and links a general RO installation video. It connects to the cold-water line only, using the included 1/2 in feed adapter and valve. You drill a 1/2 in hole for the standard faucet (1-1/4 in for an air-gap faucet) and a 1/4 in hole in the drain pipe for the drain saddle. Tubing is color-coded with quick-connect fittings. Feed water must be 40 to 85 psi, 40 to 100°F, under 2,000 ppm TDS and pH 2 to 11. The warranty doesn't cover damage from installation.
Materials	Tankless RO system with 8 stages, including a 0.0001 µm RO membrane. Waterdrop lists three replacement filters for it: G3-N1CF, G3-N3CB and G3P600-RO. The box holds the system, filters, faucet, power adapter, tubing and fittings. Waterdrop doesn't list the housing, tubing or faucet materials, or the media in each stage.	Five stages: a 5-micron polypropylene sediment filter, two 10-micron carbon block filters, a high-rejection TFC RO membrane and a 10 in coconut-shell refining carbon filter for taste. The kit includes a lead-free faucet, food-grade tubing, a stainless steel check valve and a flow restrictor. APEC doesn't state the tank's material.
Warranty	One-year warranty covering manufacturing defects, per the product page. Waterdrop's service policy says most of its RO systems get a one-year limited warranty and that terms vary by model. For a defect under warranty, Waterdrop says it can take a free return, repair the unit or send a replacement. For a damaged or wrong item, you email Waterdrop with your order details and a photo. Waterdrop also sells an extended warranty, only for products bought on its US site. It doesn't publish the length or price. The extended warranty excludes filters, products bought outside authorized Waterdrop channels, and damage from parts or filters Waterdrop didn't sell. It also requires municipal tap water at 14.5 to 87 psi and 41°F to 100°F. TDS must be under 750 ppm and hardness under 7 grains per gallon.	One year from the purchase date, covering defects in materials and workmanship. Used filter cartridges and membranes are excluded. It's void if you aren't the original purchaser, or if you run it outside normal municipal or well water conditions. The manual also voids it if you bought the unit used or from anyone other than APEC or an authorized dealer. Coverage depends on changing filters as the manual directs, and damage from non-APEC parts is excluded. A claim needs a return goods authorization number, and you pay to ship the unit to APEC. APEC's FAQ promises lifetime technical support.
Returns	30-day returns from receipt with no restocking fee, for orders within the continental US. Items must be disassembled and repacked the way they arrived. You pay return shipping unless the problem is a quality defect. After 30 days, or for items not in like-new condition, Waterdrop charges a 10% restocking fee. After 30 days it also deducts shipping from the refund. Refunds are processed within 5 working days of inspection. Orders from third-party sellers, including Amazon, don't qualify. If Waterdrop's own price drops within 30 days of purchase, it refunds the difference.	You can return it within 30 days of the invoice date with an RMA number, and it must reach APEC within 15 days of the RMA. You get a full refund, less shipping and handling, only if it's unused in unopened packaging. Opened but unused costs a 10% fee, missing parts or damage 15% to 45%, and used but not defective 50%. You pay return shipping unless the return is APEC's error or a defect. The policy covers only orders from apecwater.com.
Unresolved questions	Who certifies the NSF/ANSI 42 and 58 claims, and which contaminants a listing covers The system's power draw The membrane's TDS rejection rate The faucet-hole size Which dimension is width, depth or height Whether the MNR35 and ALK35 filters shown on the page fit the G3P600 Length and price of the extended warranty Actual output and drain water at your water pressure and temperature	The ROES-50's own pure-to-drain ratio Whether a WQA or IAPMO listing covers the ROES-50, and which contaminants it lists The membrane's TDS rejection rate How much water the tank delivers at typical home pressure, since the manual's 3.2 gallons is at 80 to 90 psi Test data behind the "Guaranteed to Remove" contaminant list Installed cost if you hire a plumber Price of O-rings, and whether the $14.95 Essence post-filter is the ROES-50's exact stage 5 part

These comparisons use published specifications, not head-to-head tests. Prices and terms are dated. Unknown costs are not zero. Check the exact variant before you buy.