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UNDER-SINK FILTER COMPARISON

Best under-sink water filters (2026): Aquasana Claryum, Waterdrop, APEC and iSpring compared

Choose the type before the brand. Filter-only systems (Waterdrop WD-10UA, $58.99; Aquasana Claryum, $449.99) send nothing to the drain. Reverse osmosis (APEC ROES-50, $230.99; Waterdrop G3P600, $539; G3P800, $999; iSpring RO500AK-BN, $692.99) needs a drain line and a faucet hole. Prices checked Nov 6, 2026.

By Comparison Updated

Skip to the prices The products compared

The bottom line

For chlorine taste on city water, the WD-10UA is $58.99. For lead or PFOA/PFOS listings without reverse osmosis, the Claryum is $449.99. For fluoride, only the G3P600 and G3P800 listings name it. For high TDS, the APEC ROES-50 costs least at $230.99. Each suits a different need, and this isn’t a ranking.

Our reviews rest on published sources, not hands-on testing. Our method

Porsche also cofounded Superhuman Chambers, which sells hyperbaric chambers · About the author.

Stock photo: Daniele Romanello / Unsplash

The products compared

These links go to each brand’s own store and earn us no commission. Prices are dated US snapshots.

In this article

The six under-sink systems side by side

Two of these six are filter-only, and four are reverse osmosis (RO). The WD-10UA and the Claryum run water through carbon cartridges. Waterdrop says the WD-10UA makes no wastewater, and Aquasana’s install steps for the Claryum have no drain connection12. The APEC ROES-50, Waterdrop G3P600, Waterdrop G3P800 and iSpring RO500AK-BN push water through an RO membrane and send part of it down the drain36.

The type decides more than the brand. In NSF’s claims guide, fluoride and nitrate claims appear only on RO systems, while lead and PFOA/PFOS claims appear on under-sink filters too7. The spread in cost is wide: $58.99 to $999 upfront, and $151.96 to $1,478.91 over three years once you add filters.

Prices are US prices on each maker’s site, dated Nov 6, 2026, before tax and shipping. Waterdrop’s pages also show lower prices with checkout codes, and we don’t count them145. Filter prices are from Oct 13 to 23, 2026. The three-year cost is the price plus three years of filters on each maker’s schedule. It leaves out installation, power, tax and drain water.

Six under-sink water filters compared on type, US price, three-year cost, drain water and power. Prices dated Nov 6, 2026
SystemBest forTypeUS pricePrice and where to buyThree years with filtersDrain water and power
Waterdrop WD-10UAChlorine taste at your existing faucetFilter-only. Feeds the faucet you already have1$58.99 list price1$58.99US price, checked Check price at Waterdrop for Waterdrop WD-10UA $151.96, with one $30.99 filter a year18No wastewater and no electricity1
Aquasana Claryum 3-Stage Max FlowLead or PFOA/PFOS listings without ROFilter-only. Own faucet, three stages9$449.99 regular price, no sale on Nov 6; stock not rechecked9$449.99US price, checked Check price at Aquasana for Aquasana Claryum 3-Stage Max Flow $1,001.93, with two $91.99 filter sets a year910No drain connection in the install steps. No outlet: a coin battery runs the change alarm210
APEC ROES-50RO at one tap with a tank under the sinkTank RO. Five stages, 4-gallon tank, faucet included11$230.9911$230.99US price, checked Check price at APEC for APEC ROES-50 $395.90, on a filter average of $54.97 a year1213Drain ratio not published for this model. No power: the manual describes a non-pumped system314
Waterdrop G3P600Tankless RO with a published drain ratioTankless RO. Own faucet, 600 GPD rating4$539 list price4$539US price, checked Check price at Waterdrop for Waterdrop G3P600 $973.91, with $144.97 a year in filters42:1 pure to drain. Needs an outlet, and the draw isn’t published4
Waterdrop G3P800Tankless RO that sends less to the drainTankless RO. Own faucet, 800 GPD rating5$999 list price5$999US price, checked Check price at Waterdrop for Waterdrop G3P800 $1,478.91, with $159.97 a year in filters5153:1 pure to drain. Needs an outlet, and the draw isn’t published5
iSpring RO500AK-BNTankless RO with an alkaline stageTankless RO. Adds an alkaline stage, 500 GPD rating6$692.996$692.99US price, checked Check price at iSpring for iSpring RO500AK-BN Tankless Reverse Osmosis System $1,202.99, on a filter average of $170 a year616Up to 2:1 pure to drain. Power isn’t published6

These links go to each brand’s own store and earn us no commission.

Filter-only, tank RO or tankless RO: which type fits

Start with what you want out of the water, then the space under your sink. A filter-only system keeps things simple and cheap to run. RO covers more contaminants on paper, but it needs a drain, takes more room and costs more in filters. Tankless RO has no storage tank. The Waterdrop systems need an outlet, and iSpring doesn’t publish its power needs46.

Which under-sink type suits which situation, with the main catch
TypeSystems hereSuits you ifThe catch
Filter-only, uses your faucetWaterdrop WD-10UAYou’re on treated city water and want less chlorine taste without drilling anything117The listing covers chlorine, taste and odor only. It doesn’t establish lead, PFAS or mercury reduction17
Filter-only, own faucetAquasana ClaryumYou want lead or PFOA/PFOS reduction at a separate tap and don’t want RO18Filters cost about $184 a year, and the warranty lasts one year1019
Tank ROAPEC ROES-50You want RO at one sink for the least money and can spare room for a tank11WQA lists TDS reduction only, and output falls from 50 GPD at 60 psi to 30 GPD at 50 psi1120
Tankless ROWaterdrop G3P600, Waterdrop G3P800, iSpring RO500AK-BNYou want fast RO flow with no tank and have an outlet by the sink45They cost $539 to $999 upfront, and filter bills run $144.97 to $170 a year46

Which one fits which need

Each suits a different need, and this isn’t a ranking. The sections below cover certifications, running cost, drain water, installation and renting. For one-on-one detail, Claryum vs WD-10UA, G3P600 vs G3P800 vs iSpring and Waterdrop vs Aquasana go further.

  • Chlorine taste at your existing faucet: Waterdrop WD-10UA. It’s $58.99, and IAPMO R&T lists it with the WD-RF10 under NSF/ANSI 42 for chlorine, taste and odor117. A filter is $30.99 a year8. The catch: the separate NSF/ANSI/CAN 372 listing covers the system’s lead content, not lead removal, and Waterdrop’s heavy-metal claims name no lab or standard121.
  • Lead or PFOA/PFOS reduction without RO: Aquasana Claryum 3-Stage Max Flow. WQA lists it under NSF/ANSI 53 for lead and PFOA/PFOS, and Aquasana’s data sheet reports lead down 99.6% at pH 8.5 and PFOA/PFOS down 99.7%1822. It’s $449.99 at the regular price, and it was $224.99 in a 50% off sale on Oct 309. The catch: filters run $183.98 a year, and the data sheet doesn’t cover arsenic, fluoride or nitrate1022.
  • RO at one tap for the least money: APEC ROES-50. It’s $230.99 with a 4-gallon tank and a lead-free faucet, and filters average $54.97 a year1113. The catch: WQA lists TDS reduction only, though APEC’s page also names lead, fluoride and PFAS, with no test data behind that list1120. Output depends on your water pressure.
  • Tankless RO that publishes its drain ratio: Waterdrop G3P600. It’s $539 and rated at 600 GPD with a 2:1 pure-to-drain ratio4. IAPMO R&T lists the base WD-G3P600 under NSF/ANSI 58 for TDS, fluoride, cadmium, barium, radium and lead23. The catch: the listings name the base model, not the Black Faucet kit or the retail cartridges, and the power draw isn’t published423.
  • Tankless RO that sends less to the drain: Waterdrop G3P800. It’s $999, rated at 800 GPD and 3:1 pure to drain5. It has the same IAPMO R&T scope as the G3P600, at $460 more upfront and $15 more a year in filters523. The catch is the same kit-versus-listing gap, plus an unpublished power draw.
  • Tankless RO with minerals added back: iSpring RO500AK-BN. It’s $692.99 and adds an alkaline remineralization stage, though iSpring doesn’t say which minerals or how much6. NSF lists it under NSF/ANSI 58 for TDS reduction24. The catch: that’s the only certified claim, and the 2-year filter pack is $339.991624.

What each system is certified for

A listing names the contaminants a certifier tested a model for. NSF/ANSI 42 covers aesthetic claims such as chlorine, taste and odor. NSF/ANSI 53 covers contaminants with a health effect, such as lead and PFOA/PFOS. NSF/ANSI 58 covers RO systems, and 401 covers emerging compounds25. NSF says a certification doesn’t mean a filter reduces every possible contaminant, so check the claim for the one you care about25.

Only the Claryum and the two Waterdrop RO systems carry listings for lead and PFOA/PFOS, and the Waterdrop listings are for the base model, not the Black Faucet kit182326. The APEC and iSpring listings cover TDS reduction only2024. The longer lists on the iSpring and APEC pages, such as iSpring’s up to 98% lead and APEC’s PFAS claim, name no standard or lab611.

For PFAS, EPA’s home-filter fact sheet says to choose a filter certified under NSF/ANSI 53 or 58. It also says that, as of April 2024, certifications didn’t yet show a filter will remove PFAS down to EPA’s new limits27. Our water filter certification guide explains that gap, and the certification checker shows how to look up a model. For how these compare with pitchers, countertop and whole-house filters on PFAS, see best water filters for PFAS.

What each system’s certifier listing names, and what it leaves out
SystemCertifier and standardNamed in the listingNot covered by the listing
Waterdrop WD-10UAIAPMO R&T: NSF/ANSI 42, and NSF/ANSI/CAN 3721721Aesthetic chlorine, taste and odor, at 0.75 GPM and 11,000 gallons17Lead removal. The 372 listing is the product’s lead content21
Aquasana Claryum 3-Stage Max FlowWQA: NSF/ANSI 42, 53 and 401182829Chlorine and chloramine taste and odor (42). Lead, PFOA, PFOS, asbestos, cysts, mercury and VOCs, among others (53). 15 emerging compounds and microplastics (401)182829Arsenic, fluoride, nitrate, TDS, bacteria and viruses1822
APEC ROES-50WQA: NSF/ANSI 5820TDS reduction, at 34.8 GPD daily production20Lead, fluoride, PFAS and pathogens20
Waterdrop G3P600IAPMO R&T: NSF/ANSI 58, 42 and 53232630TDS, fluoride, cadmium, barium, radium and lead (58). Chlorine, taste and odor (42). PFOA and PFOS (53)232630The Black Faucet kit and the retail cartridges are not named423
Waterdrop G3P800IAPMO R&T: NSF/ANSI 58, 42 and 53232630The same scope as the G3P600232630The Black Faucet kit and the retail cartridges are not named523
iSpring RO500AK-BNNSF: NSF/ANSI 5824TDS reduction, at 500 GPD. A lead-free plumbing note covers the materials24Lead and fluoride removal, which iSpring claims without a named standard624

What each costs over three years

Filters add $31 to $184 a year, enough to put the Claryum above the G3P600 over three years. The WD-10UA is $58.99 plus $30.99 a year, or $151.96 over three years18. The APEC is the cheapest of the four RO systems to own at $395.90, a gap of $578.01 to the G3P600 at $973.9141213. The Claryum, a filter-only system, comes to $1,001.93 because it uses two $91.99 sets a year10.

The iSpring comes to $1,202.99 on a 2-year pack at $339.99, and the G3P800 to $1,478.9151516. Heavier use shortens every schedule: the G3 systems’ timed filter lives work out to about 3 gallons of filtered water a day, and the Claryum’s 800 gallons in six months is about 4.4 gallons a day410. If you change the APEC’s pre-filters every 6 months, its filters average about $84.92 a year and three years come to about $485.751213.

These figures leave out installation, tax, shipping, power and the water that goes down the drain. No maker prices installation. Waterdrop and iSpring don’t publish power draw, so their electricity cost is unknown. Our three-year cost guide has the same figures beside the pitchers, countertop RO and whole-house filters.

Replacement filters and three-year cost for six under-sink systems. Filter prices checked Oct 13 to 23, 2026
SystemWhat you replacePer yearThree-year cost before installation
Waterdrop WD-10UAWD-RF10 cartridge ($30.99), rated for 12 months8$30.99$151.9618
Aquasana Claryum 3-Stage Max FlowAQ-C3M-R filter set ($91.99), rated for 6 months or 800 gallons10$183.98$1,001.93910
APEC ROES-50Pre-filter set ($29.95) one year, then the complete set ($79.99) the next1213$54.97 on a two-year average$395.901113
Waterdrop G3P600Two G3-N1CF ($29.99 each), one G3-N3CB ($29.99) and half a G3P600-RO ($109.99)4$144.97$973.914
Waterdrop G3P800Two G3-N1CF ($29.99 each), one G3-N3CB ($29.99) and half a G3P800-N2RO ($139.99)515$159.97$1,478.91515
iSpring RO500AK-BNF7-RO500AK 2-year pack ($339.99)16$170 on a two-year average$1,202.99616

Drain water, and what reverse osmosis removes

RO sends part of the incoming water down the drain. Waterdrop rates the G3P600 at 2:1 pure to drain, so about 1 gallon goes down the drain for every 2 you get, and the G3P800 at 3:145. iSpring rates the RO500AK-BN at up to 2:1 and says that cuts waste by up to 400% against traditional RO, with no baseline or test conditions given6. APEC doesn’t publish a ratio for the ROES-50. Its FAQ puts under-sink systems in general at about 3 gallons wasted per gallon made, written the other way round from Waterdrop’s ratios3.

Those are the makers’ ratings, and real drain volume varies with pressure, temperature and the TDS of your water. The extra water adds to your bill, and we don’t estimate that cost because it depends on local rates. The two filter-only systems have no drain at all12.

RO doesn’t sort useful minerals from contaminants. iSpring lists calcium and sodium among what its system removes, then adds minerals back in a third stage without saying which ones6. Whether lower minerals in drinking water matter for health is unsettled, and our evidence review covers the studies. For fluoride or nitrate, RO is the only type with certified claims on NSF’s list7.

Installation, space and warranty

The WD-10UA is the simplest install. It connects to the cold-water line and feeds your existing faucet, so there’s no extra hole to drill1. The Claryum needs a faucet hole at least 1/2 in wide, and a sprayer or soap-dispenser hole works. If you need a new hole, Aquasana’s manual strongly recommends a professional2. The APEC is a do-it-yourself job that means drilling a 1/2 in hole for the faucet and a 1/4 in hole in the drain pipe1114.

Waterdrop calls the G3 systems a 30-minute install with no plumber, but it doesn’t publish a faucet-hole size45. iSpring calls the RO500AK-BN a do-it-yourself job and doesn’t publish the faucet-hole size, drain hardware or pressure range6. Tankless doesn’t mean small. The G3 systems measure 18.11 × 5.67 × 17.73 in and weigh 32.4 lb, and the iSpring is 17.5 × 5.12 × 16.25 in at 25 lb46. The APEC’s manual asks for about 17 × 6 × 18 in plus an 11 in wide tank, and the WD-10UA is only 3.9 × 3.6 × 12.3 in11114.

All six carry a one-year warranty. Aquasana extends the Claryum’s for members of its free Water for Life program19. APEC’s is void if you buy from anyone other than APEC or an authorized dealer, and iSpring’s requires registration3132. Waterdrop sells an extended warranty only on its US site and doesn’t publish its length or price33.

  • Waterdrop WD-10UA: 30 days from receipt on orders from Waterdrop, with no restocking fee if it comes back like new. You pay return shipping unless it’s defective33.
  • Aquasana Claryum: 90 days from the order date on direct purchases, for the whole system. You pay return shipping, and the policy doesn’t say whether an installed system qualifies34.
  • APEC ROES-50: 30 days with an RMA number. A full refund, less shipping, needs it unused in unopened packaging. Opened but unused loses 10%, and a used unit that isn’t defective loses 50%1135.
  • Waterdrop G3P600 and G3P800: 30 days with no restocking fee if the unit is like new and repacked as it arrived. The policy doesn’t say whether an installed system counts as like new33.
  • iSpring RO500AK-BN: a 30-day guarantee on unused items. An opened item that isn’t defective loses 15%, and you pay return shipping unless it’s defective32.

If you rent: which to skip

Nothing in the install steps we read is written for renters, so ask your landlord before you drill or tap a drain. The question is how many holes and connections each system needs.

  • The WD-10UA needs no new hole and feeds the faucet you already have1. It’s the easiest to live with in a rental.
  • The Claryum works without drilling only if you have a spare sprayer or soap-dispenser hole at least 1/2 in wide2.
  • Skip the APEC if you can’t drill. It needs a 1/2 in faucet hole and a 1/4 in hole in the drain pipe1114.
  • Skip the G3P600, G3P800 and iSpring unless you can use a drain saddle, a faucet hole and an outlet under the sink46. The returns policies don’t say whether an installed unit can go back, so don’t count on a refund once it’s installed.

When an under-sink system is the wrong tool

Check your water report or well test before you compare prices. The makers’ own pages rule out several jobs.

  • Bacteria or viruses in well water: APEC’s manual says the system needs disinfection before or after it on microbiologically unsafe water, and Aquasana says well-water use needs a UV add-on for bacteria and viruses914.
  • Every tap in the house: an under-sink system serves one sink. See best whole-house water filters for the main-line options.
  • No plumbing at all: a countertop RO unit needs only an outlet. See AquaTru Classic vs Carafe. For a pitcher, start with the water filter guide.
  • PFAS at the new federal limits: EPA said in 2024 that certifications didn’t yet show a filter will remove PFAS down to its new limits27.

Keep reading

Water filters: our picks and whyAquasana Claryum vs Waterdrop WD-10UA under-sink filtersWaterdrop G3P600 vs G3P800 vs iSpring RO500AK-BN: tankless reverse osmosis comparedWaterdrop vs Aquasana: under-sink and whole-house filters comparedWhat a water filter costs to own over three yearsWater filter certifications, explainedBest whole-house water filters: four comparedAquaTru Classic vs Carafe countertop reverse osmosisBest water filters for PFAS (2026): which reviewed filters are certified, which only publish lab resultsBest water filter pitchers (2026)

Sources

  1. Under Sink Water Filter | Direct Connect Filtration System (WD-10UA) Waterdrop · manufacturer
  2. AQ-6200, AQ-6300 and AQ-6300M Owner's Manual Aquasana · manufacturer
  3. F.A.Q. Reverse Osmosis Water Filtration Systems APEC Water Systems · manufacturer
  4. Waterdrop G3P600 Undersink Tankless Reverse Osmosis System - Black Faucet Waterdrop · manufacturer
  5. Waterdrop G3P800 Undersink Tankless Reverse Osmosis System - Black Faucet Waterdrop · manufacturer
  6. iSpring RO500AK-BN NSF Certified Tankless Reverse Osmosis Water Filtration System iSpring · manufacturer
  7. Contaminant Reduction Claims Guide NSF · certifier
  8. Replacement Undersink Water Filter WD-RF10, WD-RF15, WD-RF17 store listing Waterdrop · manufacturer · price read from the store’s product data
  9. Claryum 3-Stage Max Flow, Chrome (SKU 100391705) Aquasana · manufacturer
  10. Claryum 3-Stage Max Flow Filter Replacements (AQ-C3M-R) Aquasana · manufacturer
  11. ROES-50 - Essence 5-stage 50 GPD Reverse Osmosis Water System for Drinking Water, WQA Certified APEC Water Systems · manufacturer
  12. APEC RO Replacement Filters Pre-filter Set for All ESSENCE Reverse Osmosis Systems (Stages 1-3) APEC Water Systems · manufacturer
  13. APEC RO Replacement Filters Complete Filter Set for ESSENCE ROES-50 System (Stages 1-5) APEC Water Systems · manufacturer
  14. APEC ROES-50 Owner's Manual (Essence RO system), copy hosted by ESP Water Products APEC Water Systems · manufacturer
  15. WD-G3P800-N2RO Filter for Waterdrop G3P800 Reverse Osmosis Systems | 800GPD Waterdrop · manufacturer
  16. iSpring F7-RO500AK NSF/ANSI 58 Certified 2-Year Replacement Filter Pack for RO500AK Tankless Reverse Osmosis Water Filtration System iSpring · manufacturer
  17. IAPMO W-11590: WD-10UA with WD-RF10, NSF/ANSI 42-2022 IAPMO R&T · certifier
  18. WQA Aquasana AQ-6300M: NSF/ANSI 53 Water Quality Association · certifier
  19. Claryum 2, 3 and 3+ Stage 1-Year Limited Warranty Aquasana · manufacturer
  20. WQA certified reverse osmosis units: APEC ROES-50, NSF/ANSI 58 Water Quality Association · certifier
  21. IAPMO W-13936: WD-10UA, NSF/ANSI/CAN 372-2022 IAPMO R&T · certifier
  22. AQ-6300M Performance Data Sheet Aquasana · manufacturer
  23. IAPMO R&T WC-13976: Waterdrop G3P600/G3P800, NSF/ANSI 58 IAPMO R&T · certifier
  24. NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems listings: iSpring Water Systems LLC NSF · certifier
  25. NSF Standards for Water Treatment Systems NSF · certifier
  26. IAPMO R&T WC-14805: Waterdrop G3P600/G3P800, NSF/ANSI 53 IAPMO R&T · certifier
  27. Reducing PFAS in Your Drinking Water with a Home Filter (fact sheet) US Environmental Protection Agency · regulator
  28. WQA Aquasana AQ-6300M: NSF/ANSI 42 Water Quality Association · certifier
  29. WQA Aquasana AQ-6300M: NSF/ANSI 401 Water Quality Association · certifier
  30. IAPMO R&T WC-14301: Waterdrop G3P600/G3P800, NSF/ANSI 42 IAPMO R&T · certifier
  31. Warranty APEC Water Systems · manufacturer
  32. Refund policy (returns and warranty) iSpring · manufacturer
  33. Service Policy (returns, warranty, shipping and price match) Waterdrop · manufacturer
  34. Refunds, Returns & Cancellations Aquasana · manufacturer
  35. Shipping and returns APEC Water Systems · manufacturer

How this was written. Written from the sources listed above, checked . It is general information, not medical advice. Talk to a clinician before acting on anything here if you have a health condition or take medication.

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