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Buying guide

Best tankless reverse osmosis system: six under-sink picks from Frizzlife, SimPure, Express Water, iSpring, APEC and Waterdrop

Last reviewed October 14, 2026

Quick answerFrizzlife's non-electric M800-Basic, $319.99, is the lowest price here. Pick Waterdrop's G3P800, $999.00, for IAPMO R&T certification to NSF/ANSI 42, 53 and 58 per Waterdrop, or iSpring's RO800G, $527.99, for less.

Best tankless reverse osmosis system: the short answer

Frizzlife's non-electric M800-Basic, at $319.99, is the lowest-priced of the six tankless reverse osmosis (RO) systems below. Waterdrop's G3P800, at $999.00, is the pick for IAPMO R&T certification to NSF/ANSI 42, 53 and 58 per Waterdrop, and iSpring's RO800G, at $527.99, has the same 800 GPD rating for less. Prices are one-time prices as read on October 14, 2026; Waterdrop's filters are extra.

Tankless means no storage tank; Waterdrop's units use a pump that needs power, while the M800-Basic is non-electric. GPD, gallons per day, is a membrane rating, not the speed at the tap. A ratio such as 3:1 is gallons of treated water per gallon sent to the drain. Tankless vs tank reverse osmosis system explains the tank design.

Six tankless reverse osmosis systems, one-time prices as read on October 14, 2026
SystemPriceRated outputCertification line
Frizzlife M800-Basic$319.99900 GPD, non-electricNSF/ANSI 58 and 372, per Frizzlife
SimPure T2-600T$389.99600 GPDSGS test reports, per SimPure
Express Water Model 6 ROT600MBN$394.99 one-time600 GPDNo NSF line on its page
iSpring RO800G$527.99800 GPDIts page names no certifier
APEC ROTL-A1000$599.001000 GPDAPEC says NSF 372 and 58 Certified, tested by IAPMO
Waterdrop G3P800$999.00800 GPD, 3:1IAPMO R&T to NSF/ANSI 42, 53, 58, per Waterdrop

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Waterdrop G3P600, G3P800 and X12

The G3P600 is $539.00, 600 GPD with a 2:1 ratio. The G3P800 is $999.00, 800 GPD with a 3:1 ratio, and IAPMO R&T's directory lists the WD-G3P800 under NSF/ANSI 42, 53, 58 and 372, which matches Waterdrop's page. The X12 is $1,299.00, 1200 GPD, 3:1, with a 2-year warranty where the G3P600 and G3P800 carry 1 year. The Remineralization Filter Bundle adds minerals back after RO: the G3P600 with it is $566.99 and the G3P800 $1,026.99.

Waterdrop's G3P600 page prints three different certification lists, and its X12 page lists many reduced substances while the WD-X12's NSF/ANSI 58 row in IAPMO R&T's directory names one reduction claim, TDS. Waterdrop G3P600 vs G3P800 sets out the G3P600 lists.

Frizzlife M800-Basic and iSpring RO800G

Frizzlife's M800-Basic is $319.99 and 900 GPD. Frizzlife says it needs no electricity or storage tank and that it is independently tested and certified to NSF/ANSI 58 and 372. iSpring's RO800G is $527.99 and 800 GPD, with a ratio of up to 2.5:1 per iSpring, and its page names no certifier. iSpring's refund policy takes back non-defective open-box returns within 30 days less a 15% restocking fee.

Pick Frizzlife for the lowest one-time price and no outlet under the sink. Pick iSpring for 800 GPD at $527.99; Waterdrop vs iSpring sets it beside the G3P800.

SimPure T2-600T, Express Water Model 6 and APEC ROTL-A1000

SimPure's T2-600T is $389.99 and 600 GPD, and SimPure says independent SGS test reports are available. SGS is a testing lab, so that is a lab report, not an NSF or IAPMO listing. Express Water's Model 6 is $394.99 and 600 GPD, and its page prints no NSF line. Express Water preselects a replenishment subscription, so $394.99 here is its one-time price.

APEC's ROTL-A1000 is $599.00 and 1000 GPD, and APEC says it is NSF 372 and 58 Certified, tested and certified by IAPMO. The Model 6 lists a 100 to 240V power supply and the ROTL-A1000 a 120V rating, so each needs an outlet.

Fit before you buy: drain, outlet, pressure and hard water

Waterdrop's G3P600 page says the system needs a drain line nearby, one outlet under the sink, feed water at 14.5 to 87 psi and about a 1-inch gap to the cabinet wall. Waterdrop's compare page says the X16, X12 and G3P800 need a hole drilled in the countertop for the faucet.

Waterdrop's FAQ puts the source-water limit for its RO systems at 500 TDS (ppm), while its extended-warranty terms allow 750 ppm and 7 grains of hardness, so get a TDS reading first. EPA's WaterSense page says a typical point-of-use RO system sends five gallons or more of reject water to the drain per gallon treated, and a WaterSense-labeled system must send 2.3 gallons or less.

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Keep exploring

Related guides

Waterdrop G3P600 vs G3P800: output, pure-to-drain ratio, price and filters Pick the G3P600 at $539.00 unless you want less drain water: Waterdrop rates the G3P800, $999.00, at one gallon to the drain for three of pure water, against one for two. For 800 GPD for less, see iSpring.Tankless vs tank reverse osmosis system: cabinet space, power, drain water and price Choose tankless if the cabinet is tight and there is an outlet under the sink, since most tankless pumps need one. Choose a tank system for stored water or a lower price, such as iSpring's RCC7 at $229.99.Best under sink water filter: carbon, ultrafiltration and tank reverse osmosis picksWaterdrop's Direct Connect WD-10UA, $58.99, works with your existing faucet. Aquasana's Claryum, $349.99, names NSF/ANSI 53 with P473; for reverse osmosis, iSpring's RCC7 tank system is $229.99.

Sources used for this page

The facts above come from the pages below, read on October 14, 2026. Prices and terms change, so confirm them on the vendor's site before you buy.

  1. Frizzlife M800-Basic non-electric tankless RO system — Vendor product page · frizzlife.com · read October 14, 2026
  2. SimPure T2-600T tankless RO system — Vendor product page · simpurelife.com · read October 14, 2026
  3. Express Water Model 6 tankless RO system — Vendor product page · expresswater.com · read October 14, 2026
  4. iSpring RO800G tankless reverse osmosis system — Vendor product page · ispringfilter.com · read October 14, 2026
  5. iSpring refund policy — Vendor legal page · ispringfilter.com · read October 14, 2026
  6. APEC ROTL-A1000 tankless RO system — Vendor product page · apecwater.com · read October 14, 2026
  7. 800 GPD Tankless Reverse Osmosis System - Waterdrop G3P800 — Vendor product page · waterdropfilter.com · read October 14, 2026
  8. G3P600 Reverse Osmosis System - Waterdrop G3P600 — Vendor product page · waterdropfilter.com · read October 14, 2026
  9. Waterdrop X Series Reverse Osmosis System, X12 — Vendor product page · waterdropfilter.com · read October 14, 2026
  10. G3P800 with Remineralization Filter Bundle — Vendor product page · waterdropfilter.com · read October 14, 2026
  11. G3P600 with Remineralization Filter Bundle — Vendor product page · waterdropfilter.com · read October 14, 2026
  12. IAPMO R&T certificate WC-13976, NSF/ANSI 58 (reverse osmosis) — Independent · myplc.iapmo.org · read October 14, 2026
  13. IAPMO R&T certificate WC-14301, NSF/ANSI 42 — Independent · myplc.iapmo.org · read October 14, 2026
  14. IAPMO R&T certificate WC-14805, NSF/ANSI 53 — Independent · myplc.iapmo.org · read October 14, 2026
  15. IAPMO R&T certificate WC-13977, NSF/ANSI/CAN 372 — Independent · myplc.iapmo.org · read October 14, 2026
  16. Waterdrop frequently asked questions — Vendor documentation · waterdropfilter.com · read October 14, 2026
  17. Waterdrop service policy — Vendor legal page · waterdropfilter.com · read October 14, 2026
  18. EPA WaterSense: Point-of-use reverse osmosis systems — Independent · epa.gov · read October 14, 2026