Costco is featuring several reverse osmosis and water-filtration products in 2026, with savings appearing on select systems and related equipment. Current Costco listings include discounted reverse osmosis systems from iSpring, Brondell and Pure Blue, along with broader water-treatment promotions from EcoWater.
For households considering an under-sink reverse osmosis system, the current Costco lineup provides several price points and designs to compare. The biggest discounts currently shown include $50 off the iSpring 6-stage Alkaline Reverse Osmosis Water Filtration System and $80 off the Brondell Circle Reverse Osmosis Water Filtration System.
Costco's water-filtration category also includes replacement membranes and filter packs, making ongoing maintenance part of the overall cost calculation.
One of the most notable current Costco promotions is the iSpring 6-stage Alkaline Reverse Osmosis Water Filtration System and Faucet.
Costco currently lists the system at $149.99 after $50 off. The product includes six filtration stages, alkaline remineralization and a faucet. Costco also states that one set of Stage 1–3 replacement filters is included.
The system is listed as NSF/ANSI certified and has a current Costco customer rating of about 4.5 stars.
A multi-stage RO system generally combines several types of filtration.
The stages can include:
The exact function of each stage depends on the system design.
Reverse osmosis is particularly useful for reducing dissolved substances that conventional carbon-only filtration may not address as effectively.
The iSpring system includes alkaline remineralization.
Reverse osmosis can remove minerals along with other dissolved substances. A remineralization stage adds selected minerals back into the treated water.
This feature is primarily related to water taste and mineral content rather than making the RO process itself more effective at contaminant reduction.
Another major Costco promotion is the Brondell Circle Reverse Osmosis Water Filtration System.
Costco currently lists the Brondell Circle at $289.99 after an $80 discount. The product is sold online only.
The Circle system emphasizes water efficiency and compact under-sink installation.
Costco lists features including:
The manufacturer design is intended to reduce wasted water compared with conventional RO systems.
Traditional reverse osmosis systems can send some water down the drain during the filtration process.
The amount depends on system design, water pressure, membrane condition and other factors.
The Brondell Circle specifically emphasizes water-saving technology. Costco states that the system uses a smart valve and flexible tank to improve water efficiency, while automatic filter flushing helps extend membrane life.
For households concerned about water waste, this feature can be an important consideration when comparing RO systems.
Costco also lists the Pure Blue 1:1 Reverse Osmosis Water Filtration System.
The current Costco comparison listing shows the system at $189.99. The system uses a high-production, high-recovery membrane and includes an electronic monitor faucet and a 3-gallon storage tank.
The system also uses advanced carbon-block filtration and a twist-lock filter design.
The "1:1" designation refers to the system's water recovery ratio. A higher recovery ratio means less water is discarded relative to the volume of purified water produced.
Buying an RO system is only the initial expense.
Filters and membranes require periodic replacement.
Costco currently lists a Pure Blue 1-Year Filter Pack at $39.99. The pack contains two sediment filters, two pre-carbon filters and one post-carbon filter.
Costco also lists a Pure Blue high-efficiency replacement membrane for $57.99. The membrane is designed for compatible Pure Blue 1:1 RO systems and is certified to NSF/ANSI Standard 58 when used in specified models.
This makes replacement costs an important part of the long-term comparison.
Reverse osmosis is a water-treatment process that uses pressure to push water through a semipermeable membrane.
The membrane allows water molecules to pass while restricting many dissolved substances.
A typical household RO system combines the membrane with additional filters.
A simplified system can include:
The exact configuration differs by manufacturer.
Reverse osmosis systems are commonly installed to improve drinking and cooking water.
Potential reasons include:
Costco describes RO systems in its water-filtration category as systems designed to remove up to 99% of impurities, although the exact reduction depends on the contaminant, system and certification.
A filtration claim should therefore be evaluated against the specific contaminant and the manufacturer's certification rather than interpreted as removal of every substance.
Certification can be more useful than simply counting filtration stages.
The NSF/ANSI standards relevant to water filtration establish testing and performance requirements for particular contaminants and system types.
Costco's current listings identify NSF/ANSI certification for several products.
For example, the iSpring system is described as NSF/ANSI certified, while the Pure Blue replacement membrane is identified as NSF/ANSI Standard 58 certified when used in specified systems.
The specific certification should be checked against the contaminant of concern.