Imperial Berkey
For a big household or a shared office. It costs about $100 per gallon of capacity, a better rate than the smaller Berkeys.
Amazon $451$451
The Imperial Berkey rates 3.2 among 4.5 gal and up gravity water filters; the ProOne Big+ 3 Gal rates 3.1 among 2.5 to 3.5 gal ones. The ProOne Big+ 3 Gal costs $221.05 less ($229.95 vs $451).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
ProOne Big+ 3 Gal
A 3 gal stainless gravity filter that uses ProOne G2.0 filters. A mid-priced option, though the listing publishes little about flow, filter gallons or warranty.
Amazon $229.95$229.95
Scores side by side
These two sit in different capacity classes (4.5 gal and up and 2.5 to 3.5 gal), and each is scored against the reference points for its own class, so a rating says how well each does among its own capacity peers. How we rank explains each factor.
| Factor weight | Imperial Berkey | ProOne Big+ 3 Gal |
|---|---|---|
| Overall rating | 3.2/5 | 3.1/5 |
| Value 25% | 57 $100.22 per gallon of capacity ($451, 4.5 gal) | 73 $76.65 per gallon of capacity ($229.95, 3 gal) |
| Running cost 15% | 34 $0.047 per gallon filtered ($140.94 per element, 3,000 gal each) | 50 replacement cost or element life not published (neutral score used) |
| Capacity 15% | 67 4.5 gal tank | 33 3 gal tank |
| Certification 20% | 10 testing claims only, no certification | 30 states certification to NSF/ANSI 42 |
| Element life 15% | 100 3,000 gal rated per element | 50 element life in gallons not published (neutral score used) |
| Warranty 10% | 11 1-year warranty | 0 warranty not published, scored as none |
Specifications
| Imperial Berkey | ProOne Big+ 3 Gal | |
|---|---|---|
| Capacity and flow | ||
| Tank capacity | 4.5 gal | 3 gal |
| Price per gallon of capacity | $100.22 | $76.65 |
| Elements included | 2 | - |
| Maximum elements | 6 | - |
| Flow, fully loaded | 16.5 gal/hr | - |
| Filtration | ||
| Element type | Black Berkey carbon-media element (BB9-2) | ProOne G2.0 ceramic and carbon element, 7 in |
| Certified | Tested only | NSF/ANSI 42 |
| Certification detail | Berkey states Black Berkey Elements were tested by accredited third-party labs against ANSI/NSF protocols for 200+ contaminants. The elements are not NSF/ANSI certified. | Listing: G2.0 filters carry NSF/ANSI 42 certification and were tested by an independent lab to other NSF standards. The title also says IAPMO certified to reduce lead, total PFAS and microplastics. |
| Fluoride | Add-on filter | - |
| Running cost | ||
| Rated life per element | 3,000 gal each | - |
| Replacement element | 140.9 $ | - |
| Cost per gallon filtered | $0.047 | - |
| Build | ||
| Material | 304 stainless steel | stainless steel |
| Height | 26 in | - |
| Diameter | 10 in | - |
| Weight | 10 lb | - |
| Warranty | 1 year | - |