Ultimate Guide to Choosing a Gravity Fed Water Filter2021-02-08T16:43:18-06:00

The Ultimate Guide to Choosing a Gravity-Fed Water Filter

Find the best gravity-fed water purification system. Use our guide to evaluate your options.

Evaluate Your Concerns

There are many use cases for gravity-fed water filters. Whether it’s for home, health, outdoor, or survival start by listing your concerns and goals:


  • I’d like to drink more water, but my tap water tastes or smells unpleasant.
  • I’m concerned about lead and other heavy metals due to aging pipes / infrastructure.
  • I’d like to reduce or remove fluoride from my tap water.
  • I want to limit / prevent my family from being exposed to PFCs and other potential chemicals.
  • I’m concerned about a local factory or plant, and want to reduce or remove potential toxins from my family’s water.
  • Bottled water is expensive. I’d like a long-lasting, economical, and effective alternative.


  • I’m concerned about drinking raw water from a lake or stream while camping.
  • I don’t want to work hard to set up the system, or manually pump water.
  • I don’t want my group to complain that the system takes too long to produce purified water.
  • The system should travel easily, and be simple to stow while not in use.
  • I’m concerned about travelling to a foreign country where water conditions may not be optimal.
  • I don’t want to worry about maintaining the system or filters during my trip.


  • In a natural disaster, I may have to use flood water or another untreated source to provide for my family. I need a system that can easily address this situation without having to worry about performance or portability.
  • In a long-term survival situation, I will need filters that can be stored for years, and are tough enough to be re-primed after drying out.
  • I will need to calculate hourly/daily needs for my family, and purchase a system capable of producing sufficient quantities of purified water.

Use your goals as critical criteria during the evaluation process. For example, if you want to reduce fluoride, make sure the system can indeed reduce fluoride over an extended period of time. If you plan to use the system for camping, check test results and instructions with regards to contaminants specific to lakes, rivers and streams.

Choose a Purifier

Look at your concerns and goals. If they focus on taste and smell and you plan to use the system at home, a filter may work for your needs. If they include concerns about specific contaminants or raw, untreated water sources then you may consider a purifier instead. Keep in mind that purification is the highest standard available. Purifiers (unlike filters) are capable of greatly reducing or removing submicron viruses, bacteria and other potential contaminants.

Black Berkey® Purification Elements are classified as water purifiers because they reduce greater than 99.999% of viruses and greater than 99.9999% of pathogenic bacteria, while also removing or dramatically reducing protozoa, trihalomethanes, inorganic minerals, heavy metals, pharmaceuticals, pesticides, VOCs, petroleum products, perfluorinated chemicals, rust, silt, sediment and even radiologicals.

Research Brands

Watch out for:

  • “Too good to be true” deals
  • Bait and switch tactics
  • Fake reviews and videos
  • Hype or distracting information
  • Misinformation about competing systems
  • “New” or “revolutionary” claims with no hard data or testing to back it
  • Ads full of emotional appeals, with little product information
  • Testing data that is less impressive upon closer inspection
  • Conflicting statements in product listings

Take a close look at:

  • Web pages where you can buy the product
  • How-to videos and instructions
  • Test results
  • Product inserts instructions
  • Knowledge-base / FAQs (like http://berkeywaterkb.com/)
  • Customer testimonials and reviews (look at a wide sample)
  • Blogger recommendations

Evaluate Specific Systems

Learn how to evaluate testing, lifespan and performance concerns:

Research each system’s test results, and answer these questions:

  • How many independent labs have conducted testing for this system?
  • What contaminants were tested?
  • How many samples were taken during each test?
  • What volumes were tested for each sample?
  • What does effectiveness look like over time?

First, look at the lab report(s) and note who did the testing. There should be a company name clearly stated on each one. Do you see a variety of companies, or just one?

Next, review the specific contaminants listed in the test. If the list is particularly long, look for contaminants from three types of challenge organisms: Bacteria (Klebsiella/Raoultella terrigena), Viruses (Poliovirus and Rotavirus or MS2 bacteriophage) and Protozoan Cysts (Giardia or Cryptosporidium).

Now look closely at filtered water test results tables. You should see a column indicating parameters tested. This will tell you how many samples were taken, and what volumes were tested for each sample. Why does this matter? Because these numbers reveal an element’s effectiveness over time, and that is critical to understanding what you should expect from a system.

If the test results looks like one big list of contaminants, and you do not find any introductory material or columns indicating multiple samples were taken, then it is very likely the lab took only one sample.

Berkey® Element Testing Goes Further

Review the Black Berkey® Purification Element Laboratory Lead Water Test Results tables below. You will see multiple samples at increasing volumes were taken.

Why this matters

  • You need to know the rate of “% Reduction” drop-off to determine the lifespan of the element.
  • Multiple readings tell you what effectiveness looks like over time for various contaminants.
  • Higher volumes in lab tests give you a more accurate picture of performance.

Berkey® by NMCL used several different independent labs, took multiple samples and performed Extreme Testing for Lead and PFCs in order to review the effectiveness of our Black Berkey® Purification Elements. Test results are readily available to interested customers. In addition, a non-contracted third-party lab further confirmed the heavy metal reduction of the Black Berkey® Purification Elements.

Answer these questions:

  • What is the GALLON lifespan of each element?
  • What is the TIME limitation on the lifespan of each element?
  • Are there any disclaimers regarding the lifespan?
  • How do you calculate when to replace your elements?
  • Did test results include multiple samples, revealing % drop-off in effectiveness over time?

The first two questions are the most important in determining the lifespan. Many elements make claims such as 5,000 gallons with additional instructions in the fine print that recommend the elements be replaced after 6, 9, or sometimes 12 months. For example, if the advertised life of the filter is 5,000 gallons and the maximum flow rate is 12 gallons per day, and the instructions say to replace the elements after 6 months, then the real maximum life of the filter is 12×183 days=2,196 gallons—rather than the 5,000 gallons claimed.

Moreover, if it is recommended that an element be replaced after a fixed amount of time, let’s say 6 months of use, and you use on average 3 gallons per day, then for all practical purposes, the maximum lifespan is only 549 gallons.

Bottom line: Take a close look at the data and understand what is an element’s true calculated lifespan when there is a time limitation. Beware of conflicting or inconsistent information about an element’s lifespan, or test results that don’t reveal performance over time.

Black Berkey® Purification Elements are Reliable

A set of Black Berkey® Purification Elements is designed to last for up to 6,000 gallons, and they do not have a TIME limitation. This means they will provide many years of use before needing replacement. Lifespan calculations based on performance data are included with the product insert. The purification elements are also cleanable, eliminating frequent replacements.

Learn more: Black Berkey® Purification Elements Are One-of-a-Kind

If fluoride reduction is a crucial concern, ask yourself the following:

  • Are test results available that demonstrate fluoride reduction over time?
  • Is there a separate post filter available that has the required media to reliably remove fluoride long-term?
  • For options that claim they are all-in-one filters, how many samples and at what volumes did they test for fluoride?

Look for test results that include multiple samples for fluoride. Most carbon-based filters will initially reduce fluoride. However, they typically experience a drastic decline in their effectiveness—usually within the first 50 gallons or less. In order to ensure long term fluoride reduction, a separate fluoride reduction filter is required that provides the proper amount of media and proper contact time in order for effective long term fluoride reduction to take place.

Black Berkey® Purification Element Tests Reveal Effectiveness Over Time

For this reason, Berkey® by NMCL designed a separate, more durable and longer lasting solution for fluoride reduction. Berkey® Fluoride and Arsenic Reduction Elements (optional and sold separately) reliably reduce fluoride contaminants that the Black Berkey® purification elements begin to miss after extended use.

For more information, read:


If you plan to use the system for outdoor recreation, or would like an emergency water purification solution, ask:

  • Can you find information on using the system with raw, untreated water sources like rivers, lakes and streams?
  • Did the test results give you confidence the system will effectively perform in extreme conditions?

Contaminants like salmonella, along with bacteria and cysts, are known risks to outdoor water sources. Look carefully at test results or product documentation to see if there are disclaimers that clarify how you ought to use the system. In other words, check the fine print.

Now think back to testing: Which systems impressed you? Did you find testing data and lifespan information that gives you confidence when using the system with raw, untreated sources?

Berkey® Systems are Made for the Extreme

Berkey® systems can easily purify ordinary tap water and well water, yet are powerful enough to efficiently purify raw, untreated water from freshwater sources such as remote lakes and streams.

Learn more about outdoor water contaminants:

As a precaution, if using a source of water that you believe might contain extreme viral and bacteriological contamination, it is recommended by the CDC, EPA, and other organizations that approximately sixteen drops of plain bleach (sodium hypochlorite) or iodine per gallon be added to treat the source water before purifying. This should kill minute pathogens such as viruses within 30 minutes. If using a Berkey® system, the disinfectant will be removed from the treated water entirely along with any odor or taste.

For more information about disinfecting water, please reference the following links: cdc.gov or water.epa.gov


  • Does the filter element require special pampering to remain effective?
  • Does the company give clear instructions on long-term storage of the filter?
  • Can you reprime the filter element after it dries out?

Look at a system’s instructions to understand real-life care and maintenance requirements. Specifically, find instructions related to daily care, long-term storage and element priming. Why? Complex storage requirements can easily be overlooked. Certain filter elements require long-term storage in water, and must be replaced if they dry out completely. If you forget to pamper a high maintenance filter, it could become totally useless, at the very time when you need it the most, and leave you without any ability to purify contaminated water.

Berkey® Gravity-Fed Purification Systems Were Made for Real-World Conditions

A Black Berkey® Purification Element arrives (and can be stored) dry. If you will not use it for a period of 30 days or more, simply re-prime the element and reinstall.

Wrap Up Your Evaluation

For each finalist, review the following:

  • Warranty information
  • Shipping and return policies
  • Customer testimonials
  • Potential system accessories (like the Berkey Sight Glass™ Spigot, Berkey Primer™)
  • Instructional materials (assembly or care videos)
  • Product materials (durable, rust-resistant, attractive)
  • Ease of use and portability
  • Customer service and support


  • Powerful– Berkey® purifiers remove a broad universe of contaminants, from toxic chemicals and minerals to pathogenic bacteria and virus, while leaving in the healthy minerals your body needs.
  • Efficient– Berkey® purifiers are the fastest-producing gravity fed water purification systems on the market, purifying water up to eight times faster that other available systems.
  • Convenient– The purification elements may be cleaned, eliminating frequent replacements.
  • Effortless– The design replaces slow and exhausting manual pumps with the natural force of gravity.
  • Portable– Berkey® purifiers travel easily and function without electricity or water pressure.
  • Durable– Constructed of highly-polished surgical grade AISI 304 stainless steel, the housing is built to last.
  • Economical– Two Black Berkey® Purification Elements, which come standard with most systems, average 2 cents per gallon of purified water, and last up to 6,000 gallons, or approximately 5-8 years with typical use.
  • Proven– Used by individuals, missionaries, and relief organizations worldwide

Authentic Black Berkey® Purification Elements are the Right Choice for Your Loved Ones

Available in 7 sizes, Berkey® water purification systems are made for the extreme, yet enjoyed every day. They can easily purify ordinary tap water and well water, yet are powerful enough to efficiently purify raw, untreated water from freshwater sources such as remote lakes, rivers and streams.