Water-efficient under-sink RO review
Brondell Circle Review
A tankless under-sink RO system with a patented Smart Valve that achieves a 2.1:1 wastewater ratio — roughly ten times more efficient than conventional RO. It does not need electricity, and it saves cabinet space. The trade-off is proprietary filters and a slower flow than tank-based systems.
Brondell Circle
Tankless · 2.1:1 waste ratio · 500 GPD · no electricity · ~$399
Check price on Amazon →What the Circle actually is
The Circle is a tankless under-sink RO system that uses line pressure and a patented Smart Valve to eliminate the back-pressure that normally forces conventional RO systems to waste three or four gallons for every gallon purified. Brondell claims a 2.1:1 ratio, which is roughly ten times more efficient than older tank systems. It does not require electricity, and the circular reservoir design saves cabinet space compared with a conventional pressure tank.
The trade-off is flow rate and filter cost. Tankless systems dispense more slowly than tank-based systems, and the Circle uses proprietary filters that are more expensive per year than the APEC’s standard cartridges.
Specifications that matter
| Spec | Detail |
|---|---|
| Type | Tankless under-sink RO |
| Waste ratio | 2.1:1 (approximately 10× more efficient than conventional RO) |
| Production | 500 GPD |
| Electricity | Not required |
| Storage | 1.6 gallons (6.0 litres) |
| Upfront price | ~$399 |
| Smart features | None (mechanical indicators) |
What we liked
The waste ratio is genuinely best-in-class. 2.1:1 is not marketing — it is a measurable difference that adds up over a year. If water efficiency matters to you, no other system in this guide comes close.
No electricity and no pressure tank. The Circle saves cabinet space and does not require a power outlet under the sink. That makes it simpler to install in older kitchens.
The LED indicator faucet is a nice touch. It is not smart tracking, but it gives you a visual cue when the filter needs attention.
What we did not like
Flow is slower than tank-based systems. The 1.6-gallon reservoir and tankless design mean you may wait longer to fill a large pot than with a four-gallon tank like the APEC’s.
Proprietary filters are expensive. The Circle’s filters cost more per year than standard 10-inch cartridges, which erodes some of the running-cost advantage of the efficiency gain.
Certification is less prominent than competitors. Brondell does not lead with an IAPMO or WQA listing the way Aquasana and APEC do. If third-party certification is a priority, the Aquasana SmartFlow is a safer choice.
Who should buy it
Buy the Circle if: water efficiency is your top priority, you want to save cabinet space, and you do not need a high flow rate.
Skip it if: you need fast flow for cooking, you want the strongest certification, or you prefer standard filters that are cheap and easy to find.
Verdict
The most water-efficient RO in this guide, and a good choice for eco-conscious households with modest flow needs. Proprietary filters and slower dispensing are the price you pay.
Check price on Amazon →