Choosing water filtration starts with a practical question: do you want a plumbed reverse osmosis setup under the sink, or a countertop gravity system that sits out in the open? The four options here split clearly between multi-stage reverse osmosis systems and a stainless gravity system, with listed prices running from USD 116.09 to USD 229.99.
Quick take
- Lowest listed price: The 5 Stage Undersink Reverse Osmosis Water Filter System 75 GPD Membrane Filter is the least expensive pick and keeps the focus on a 5-stage reverse osmosis layout.
- Higher-flow RO choice: The Waterdrop D6 Reverse Osmosis Water Filter, 600 GPD Under Sink Reverse Osmosis stands out for its 600 GPD capacity, tankless design, smart faucet language, and black finish.
- Alkaline RO option: The 100 GPD 6 Stage Alkaline Reverse Osmosis Drinking Water Filter System Purifier adds an alkaline stage to a reverse osmosis system.
- Countertop gravity alternative: The BLEMISHED Berkey Water Filter System w/ WQA Certified Boroux Black Filters is the non-RO option here, with a polished stainless steel gravity format and two black filters.
Listed price comparison
The price spread is wide enough to matter: the lowest listed option is about 50% below the highest listed option. Use this table to anchor the comparison before looking at filtration style and condition.
| Product | Listed price | Price bar |
|---|---|---|
| 5 Stage Undersink Reverse Osmosis Water Filter System 75 GPD Membrane Filter | USD 116.09 | |
| 100 GPD 6 Stage Alkaline Reverse Osmosis Drinking Water Filter System Purifier | USD 135.99 | |
| Waterdrop D6 Reverse Osmosis Water Filter, 600 GPD Under Sink Reverse Osmosis | USD 179.00 | |
| BLEMISHED Berkey Water Filter System w/ WQA Certified Boroux Black Filters | USD 229.99 |
Decision matrix
Choose the 5-stage Simpure RO system if: you want the lowest listed cost, a white universal-compatible setup, and a reverse osmosis filtration method with 0.0001 micron filtration precision.
Choose the 6-stage alkaline Simpure RO system if: you like the same general RO direction but want the added alkaline filter stage described as adding minerals back for a more natural taste.
Choose the Waterdrop D6 if: the headline capacity matters most. Its 600 GPD figure is far above the 75 gal and 100 gal Simpure capacities, and the title places it clearly in the under-sink reverse osmosis category.
Choose the Berkey/Boroux bundle if: you prefer a countertop gravity system rather than an under-sink RO system. It is the only polished stainless steel option in this group and includes two black filters.
Condition may decide the shortlist: the two Simpure systems are marked new, the Waterdrop is marked certified-refurbished, and the Berkey system is marked open box with "BLEMISHED" in the title.
Concise product notes
5 Stage Undersink Reverse Osmosis Water Filter System 75 GPD Membrane Filter
This is the straightforward pick for shoppers who want a reverse osmosis system at the bottom of the listed price range. The filtration path includes sediment, granular activated carbon, compressed carbon block, RO membrane, and post-carbon stages, so it is aimed at buyers who want a classic multi-stage RO layout rather than extra features. Its universal compatible brand and model language also keeps the fit description broad. The main tradeoff is capacity: at 75 gal, it sits below the 100 gal Simpure option and far below the Waterdrop D6's 600 GPD figure. It also does not include the alkaline stage named in the 6-stage Simpure title.
100 GPD 6 Stage Alkaline Reverse Osmosis Drinking Water Filter System Purifier
The 6-stage Simpure system is the better match if you want reverse osmosis plus an alkaline stage in the same product title. It uses the familiar pre-filter, RO membrane, post-carbon, and PH+/ALK filter sequence, with the alkaline stage described around adding calcium, potassium, magnesium, and other minerals back to the water for taste. It is marked new, white, and universal-compatible, which keeps it close to the 5-stage Simpure in overall direction. The limitation is that its capacity remains modest beside the Waterdrop D6. It also costs more than the 5-stage Simpure, so the extra stage needs to matter to your choice.
Waterdrop D6 Reverse Osmosis Water Filter, 600 GPD Under Sink Reverse Osmosis
The Waterdrop D6 is the strongest fit for shoppers prioritizing output within an under-sink reverse osmosis format. Its 600 GPD capacity, tankless design, 6-stage filtration language, smart faucet with LED display, and 2:1 low drain ratio give it the most feature-heavy description among the RO options here. It is also the only black system in the group. The tradeoff is condition: it is marked certified-refurbished rather than new. It also requires an electrical outlet for operation, so it is less simple than a purely non-powered gravity system. If those points are acceptable, it offers the clearest high-capacity RO direction.
BLEMISHED Berkey Water Filter System w/ WQA Certified Boroux Black Filters
The Berkey/Boroux bundle is the outlier: it is a polished stainless steel gravity countertop system rather than an under-sink reverse osmosis unit. Choose it if you specifically want the Berkey-style format, two black filters, and compatibility language that names Berkey, Boroux, BU2, TU2, CU2, and IU2. The title also calls out WQA Certified Boroux Black Filters, which may be part of why it sits at the top of the price range. The limitations are just as clear: "BLEMISHED" appears in the title, the condition is open box, and its Big capacity is 2.25g rather than a gallons-per-day RO rating.
Final recommendation
For most shoppers comparing these four water filtration choices, start by deciding between reverse osmosis under the sink and gravity filtration on the counter. If RO is the goal and the lowest listed price matters most, the 5 Stage Undersink Reverse Osmosis Water Filter System 75 GPD Membrane Filter at USD 116.09 is the cleanest entry point. If you want the Simpure RO layout but prefer the added alkaline stage, move to the 100 GPD 6 Stage Alkaline Reverse Osmosis Drinking Water Filter System Purifier at USD 135.99.
If capacity and modern RO features are more important than condition, the Waterdrop D6 Reverse Osmosis Water Filter, 600 GPD Under Sink Reverse Osmosis is the standout because its 600 GPD capacity is the largest number in the group. If you do not want an under-sink RO system and prefer a stainless countertop gravity setup, the BLEMISHED Berkey Water Filter System w/ WQA Certified Boroux Black Filters is the distinct alternative, though it is also the highest listed price at USD 229.99.