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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 →

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, checked Oct 13, 2026

Tankless 500 GPD reverse osmosis with an alkaline stage, NSF 58 certified for TDS

Check price at iSpring Full review →

Criterion	APEC ROES-50	iSpring RO500AK-BN Tankless Reverse Osmosis System
US price	$230.99Checked Oct 13, 2026 · Price details in the review	$692.99Checked Oct 13, 2026 · Price details in the review
Three-year ownership estimate	$395.90 Incomplete known subtotal. Not included: installation.	$1,202.99 Incomplete known subtotal. Not included: installation, energy use.
Choose if	You want RO water at one kitchen sink for little money, and your water pressure is near 60 psi.	A kitchen with under-sink plumbing and a drain, if you want tankless RO with minerals added back.
Main trade-off	WQA lists 34.8 GPD and TDS reduction. APEC's 50 GPD at 60 psi and 30 GPD at 50 psi are separate manufacturer ratings, not a basis for assuming lead or PFAS certification.	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.
Key specifications	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: WQA lists ROES-50 under NSF/ANSI 58; the row-level reduction claim is TDS and the daily production rate is 34.8 GPD Power: None; the manual describes a non-pumped system Certifier-listed daily production: 34.8 GPD in the WQA listing; separate from APEC's pressure-dependent manufacturer ratings	Rated output: 500 GPD and up to 0.4 GPM (about 10 seconds to fill an 8 oz cup) Pure-to-drain ratio: Up to 2:1 Filtration: 3 stages: composite sediment and carbon block, RO membrane, carbon alkaline remineralization filter Filter life: Stage 1 (FCF500) up to 6 months, stage 3 (FCA500) up to 12 months, RO membrane (MRO500) 24 to 36 months Certification: NSF/ANSI 58 for TDS reduction, certified by NSF, at 500 gpd with the FCF500, MRO500 and FCA500 filters Auto-flush: 20-second membrane rinse after 24 hours without use Size and weight: 17.5 × 5.12 × 16.25 in, 25.0 lb Power: Not published on the product page
Exact variant	ROES-50 Essence 5-stage, 50 GPD	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	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.	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	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.	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	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.	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 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.	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	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.	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.
Unresolved questions	The ROES-50's own pure-to-drain ratio Whether separate exact-model certifications or performance data substantiate the broader lead, fluoride and PFAS claims 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 manufacturer-listed FI-ES-TCR-QC post-filter is the same part as WQA-listed FL-ES-TCR-QC	Individual prices of the FCF500, FCA500 and MRO500 replacement filters Whether it needs an electrical outlet, and how much power it draws Operating pressure, temperature and feed-water TDS limits The certified TDS reduction percentage, which NSF's listing doesn't give How much the alkaline stage raises pH or adds minerals (iSpring gives no figures) Length and terms of the extended warranty offered on registration Whether an installed system can be returned for any refund Actual drain-water volume and output at your water pressure and temperature

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.