Through the Spring and Summer of 2014, I purchased five of the most popular off-the-shelf gravity water filters which are commonly promoted and sold as emergency water filtration devices. For this test, I limited my purchase only to those filters which are non-electric and operate from the principle of gravity. In other words, no water filters with manual pumps were included.
The purpose of this testing was to subject each water filter to a known concentration of heavy metals contaminants (lead, cadmium, arsenic, mercury) as well as elements which have radioisotopes such as strontium, cesium and uranium. Aluminum was also tested, but fluoride was not tested due to the difficulty of running halogens through ICP-MS sample introduction systems. (We have a different way to test fluoride using another instrument, but its accuracy is nowhere near the ppb accuracy of ICP-MS.) Water filters were not tested for pesticides, herbicides, PCBs or other complex molecules. Also, the filters were not tested for removal bacteria, amoeba or other microorganisms.
In preparation for the tests, I created a "cocktail" of heavy metals using NIST-traceable external standards purchased from Inorganic Ventures. Each gravity filter was prepared for testing by first being flushed with its maximum holding volume of laboratory-grade deionized (DI) water, produced from a laboratory instrument manufactured by Thermo Scientific.
Once the initial flush was completed, each water filter was then filled with the heavy metals cocktail and gravity filtration was allowed to commence. Samples were taken of this "pre-filtered" water in order to compare it to the "post-filtered" results for each water filter.
After the completion of the gravity filtration, which required anywhere from 8 - 24 hours depending on the unit, the resulting water was sampled and tested via ICP-MS in the Natural News Forensic Food Lab, where I am the laboratory director.
This lab is in the process of achieving ISO 17025 certification and uses EPA-derived methodologies for sample preparation, acid digestion, normalization and ICP-MS introduction. Mid-run calibration standards are always used, and I also use 4-point multi-elemental calibration curves for each run with robust RSDs that provide very high confidence of accuracy variance within + / - 5% of reported numbers.
SUMMARY OF FINDINGS: The gravity water filter brands tested were:
Big Berkey
Zen Water Systems
ProPur
Crystal Drop
Doulton
Performance of the filters varied significantly, with some units achieving a near-100% removal rate of toxic elements (Big Berkey and Zen Water Systems) while other units showed very little ability to remove toxic heavy metals at all (Doulton).
Many units tested actually increased the level of aluminum in the filtered water. Crystal Drop filters released the most aluminum into the filtered water. ProPur filters increased aluminum by 92%, but the new "All-in-One" ProPur filters reduced aluminum by 61%. Doulton filter elements also released aluminum into the water. (Aluminum is commonly used in water filtration elements because of its flocculant properties.)
Even after flushing, ProPur's new "All-in-One" filter elements left behind a cloudy residue in the bottom of the filtration receiver. This liquid was sampled and found to contain 50 ppm of Aluminum, indicating a strong need to repeatedly flush these elements before using them to produce potable water. Big Berkey, the most prominent competitor of ProPur, did not suffer from this problem and produced extremely clean water after a single flush.
All water filters used in this test have been physically stored for future analysis. Water samples taken during the test have also been archived for future verification, if needed.
CONCLUSION: Big Berkey and Zen Water Systems produced by far the best results in these tests, removing nearly 100% of most toxic elements.
ProPur performed far worse than expected, with the older ProPur elements achieving surprisingly low reduction in toxic elements. But the new "All-in-one" ProPur elements performed significantly better, although the numbers are still far from the performance of Big Berkey.
Crystal Drop and Doulton filters performed very poorly, failing to remove significant quantities of toxic elements in our tests.
FULL DISCLOSURE OF POTENTIAL CONFLICT OF INTEREST: In the interests of scientific integrity, I am openly disclosing the fact that after I reviewed these laboratory results, Natural News, where I am the editor, formed an affiliate relationship with a distributor of Big Berkey water filters for the simple reason that we wish to publicize only the best-performing filter. This relationship was formed on the basis of Natural News seeking to represent whichever filter performed the best in our laboratory testing, and we held off on forming any affiliate relationships until testing was complete. Whatever water filter performed the best, I decided long in advance of the testing, I wanted to help promote that product.
Here at Natural News, we test first, and then we recommend the best-performing product based on the scientific data. All our test results are openly released to the public, and we welcome any other company that might dispute our tests to conduct their own ICP-MS testing for verification. (To my knowledge, no other company promoting water filters has conducted its own laboratory testing of the performance of those filters.)
Neither myself nor Natural News received any compensation nor free product for conducting these tests. All products were purchased at retail, via Amazon.com. No attempt was made to request payment of any kind from the manufacturers of these products.
We do not have any affiliate relationships with any other water filters tested here, but based on these test results, I would have no hesitation openly endorsing the Zen Water Systems technology which is clearly superior to the ProPur unit we tested.
Join the Natural News Diaspora community for 100% uncensored real-time news posts throughout the day. Diaspora is the free speech alternative to Facebook.