Our under-sink reverse osmosis pick
Waterdrop G3P600
G3P600 Black Faucet / WD-G3P600-Black
$539US price, checkedTankless RO with a TDS faucet and about $145 a year in filters
Check price at Waterdrop for Waterdrop G3P600 Full review →SIDE BY SIDE
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See prices, running costs, specifications and trade-offs side by side. Choose two to four products of the same type.
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Under sink reverse osmosis
Waterdrop G3P800
G3P800 Black Faucet / WD-G3P800-Black
$999US price, checkedTankless RO rated at 3:1 pure to drain, with a $999 list price
Check price at Waterdrop for Waterdrop G3P800 Full review →
Under sink reverse osmosis
iSpring RO500AK-BN Tankless Reverse Osmosis System
RO500AK-BN tankless, 500 GPD, 2:1 pure-to-drain ratio, 3-stage with alkaline remineralization, brushed nickel faucet; system only, without the UVF8 UV add-on
$692.99US price, checkedTankless 500 GPD reverse osmosis with an alkaline stage, NSF 58 certified for TDS
Check price at iSpring for iSpring RO500AK-BN Tankless Reverse Osmosis System Full review →Scroll the table sideways to see every product.
| Criterion | Waterdrop G3P600 | Waterdrop G3P800 | iSpring RO500AK-BN Tankless Reverse Osmosis System |
|---|---|---|---|
| US price | $539Checked Oct 13, 2026 · Price details in the review | $999Checked Oct 13, 2026 · Price details in the review | $692.99Checked Oct 13, 2026 · Price details in the review |
| Three-year ownership estimate | $973.91 Incomplete known subtotal. Not included: installation, energy use. | $1,478.91 Incomplete known subtotal. Not included: installation, energy use. | $1,202.99 Incomplete known subtotal. Not included: installation, energy use. |
| 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. | A household on city water that wants quick RO flow and less drain water than a 2:1 system. | A kitchen with under-sink plumbing and a drain, if you want tankless RO with minerals added back. |
| Main trade-off | Black-faucet and retail-cartridge mapping to the certified configuration is unverified; power draw is unpublished and the warranty is one year. | Black-faucet and retail-cartridge mapping to the certified configuration is unverified; power draw is unpublished and the warranty is one year. | Filters run about $170 a year on the 2-year pack, the product page doesn't give power needs, and opened returns lose 15% plus return shipping. |
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| Exact variant | G3P600 Black Faucet / WD-G3P600-Black | G3P800 Black Faucet / WD-G3P800-Black | RO500AK-BN tankless, 500 GPD, 2:1 pure-to-drain ratio, 3-stage with alkaline remineralization, brushed nickel faucet; system only, without the UVF8 UV add-on |
| 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. | 18.11 × 5.67 × 17.73 in and 32.4 lb, per Waterdrop's product page. Waterdrop doesn't say which measurement is width, depth or height, or how much clearance you need to swap filters. | 17.5 in L × 5.12 in W × 16.25 in H and 25.0 lb, per the product page. iSpring doesn't say how much clearance you need for filter changes. |
| 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. | It goes under the sink and connects to a water supply line, a drain and its own faucet. The box includes the faucet, a 3/8 to 1/2 in feed-water adapter, a 1/4 in drain saddle, tubing, lock clips and Teflon tape. It also needs an outlet, and a power adapter comes in the box. Waterdrop calls it a 30-minute DIY install that needs no plumbing skills. It's for indoor use only. The product page doesn't give the faucet-hole size or any water limits, and the linked user manual PDF has no searchable text. The only limits Waterdrop publishes are general ones in its extended-warranty terms, not specific to the G3P800. They call for municipal tap water at 14.5 to 87 psi and 41 to 100°F. TDS should be under 750 ppm and hardness under 7 grains per gallon. Well water needs pre-filtration. | It goes under the sink, and the product page calls installation DIY. A feed water adapter fits 1/2 in or 3/8 in supply pipes, and the product title names a brushed nickel faucet. Because it's a reverse osmosis system, it sends reject water to a drain, at a rated 2:1 pure-to-drain ratio. The product page doesn't give the drain connection hardware, faucet-hole size, operating pressure range or power requirements. iSpring says you can change filters in seconds without shutting off the water supply. The refund policy says the warranty doesn't cover installation costs. |
| 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. | A tankless unit that Waterdrop calls 10-stage, built around three replaceable filters: the G3-N1CF, the G3P800-N2RO reverse osmosis membrane and the G3-N3CB. The membrane page describes this as a 3-filter setup with a seven-layer RO membrane. Waterdrop says the membrane is 0.0001 μm, though the membrane page's FAQ says 0.001 microns. The box list includes a UV sterilizer, and the faucet's display shows TDS and filter life. Waterdrop's comparison table marks alkaline mineralization as not included. Housing, tubing and faucet materials aren't listed. | It has three stages. First comes a 2-in-1 composite sediment and carbon block filter (FCF500), listed as PP and CTO. Next is the RO membrane (MRO500). Last is a carbon alkaline filter (FCA500), which the page describes as coconut-shell activated carbon with minerals. iSpring doesn't list housing, tubing or faucet materials. |
| 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 against manufacturing defects, per the product page. Waterdrop's service policy says most of its RO systems carry a one-year limited warranty and that terms vary by model. If it fails from a quality problem during the warranty, Waterdrop will take it back, repair it or replace it for free. The policy's extended-warranty terms apply only to purchases from Waterdrop's US website. They exclude filters and damage from well or river water. They also exclude damage from incorrect installation, use or maintenance, or from unauthorized repairs. The policy asks you to report a defect within 30 days of finding it. It doesn't say how the extended terms relate to the standard one-year warranty. Waterdrop also offers lifetime technical support for eligible models. | The product page lists a one-year manufacturer warranty, and the refund policy fills in the terms. It covers defects in materials and workmanship for one year from the date of purchase. You must register at ispringfilter.com to be eligible. It applies only to products bought from an authorized iSpring dealer or reseller. The only remedy is repair or replacement, at iSpring's option. A repaired or replacement product is covered for the rest of the original period or 6 months, whichever is longer. Installation and reinstallation costs aren't covered. The product page mentions an extended warranty on registration but doesn't give its length or terms. iSpring also lists lifetime phone and technical support from Atlanta, GA. |
| 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. | 30-day returns, counted from receipt, for orders within the continental US. Items must be disassembled and repacked as received, in the original packaging with the receipt. There's no restocking fee within 30 days, but you pay return shipping unless the return is for a quality problem. After 30 days, Waterdrop charges a 10% restocking fee and deducts shipping from the refund. An item that isn't like new also carries a 10% fee. If it arrives damaged or wrong, email service@waterdropfilter.com with your order details and a photo. Orders from Amazon and other third-party sellers aren't covered. The policy doesn't say whether an installed system counts as like new. | The product page lists a 30-day money-back guarantee, but the refund policy attaches conditions. A full refund within 30 calendar days of purchase applies only to a product in its original packaging that hasn't been used or damaged. Open-box items within 30 days are refunded minus a 15% restocking fee. They qualify only if they aren't defective, include all parts, and are unused, undamaged and in good working order. Later returns are prorated. Unopened items get 85% back at 1 to 3 months, 65% at 3 to 6 months and 50% at 6 to 12 months. Open-box items get 70% at 1 to 3 months and 50% at 3 to 6 months. Unopened items can't be returned after 12 months, and open-box items after 6 months. You pay return shipping unless the item is defective. For a defective item, iSpring provides a prepaid label and refunds in full once the defect is confirmed. Customers in Hawaii, Alaska, Puerto Rico and outside the US pay shipping and any destination charges. Every return is subject to inspection and approval. The policy doesn't say whether an installed system counts as used. |
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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.