Gravity Feed Water Filter – A Godsend During Emergencies

For these uncertain times...

Gravity Feed Water Filter – A Godsend During Emergencies

March 26, 2018 All posts Prepare Solution 0

So, why should you consider a gravity feed water filter?

A Year of Records

The year 2017 has broken all records and now stands as the costliest year for natural disasters in the United States since the NOAA (National Oceanic and Atmospheric Administration) started keeping records in 1980.   Huge swaths of the continental United States were impacted by these natural calamities, whilst hundreds of thousands of American’s lives were touched in the process:  from the massive damage caused by hurricanes Harvey, Irma and Maria costing into the hundreds of billions of dollars, to the widespread droughts and the devastating wildfires of the West, to the flooding in states such as Missouri, Arkansas and California, to severe weather systems hitting the midwest.  And now 2018 is shaping up to be potentially as bad, with the extensive snowstorms and flooding hitting the Northeast in late winter, early spring.

It’s as if the weather system has become unhinged, and we are seeing a crescendo in devastation across the board. Mind you, all of this on top of the geopolitical instabilities we face today makes one wonder why so many folks are still treating today just like any other day and not preparing for what tomorrow might bring.  Any sort of civil emergency, be it of the nature of the calamities listed above, a grid-down scenario, or civil unrest, can cause disruptions in our water supply.

How Long Can You Survive Without Water

The human body can go for up to three weeks without food, but we are much more vulnerable when it comes to water.   Without water, we will only last three or four days.  And if we, out of desperation, consume just any (unfiltered) water that we may find, we are opening ourselves up to any number of water-borne diseases, such as cholera and dysentery.  That is why it so important to be able to supply yourself with clean, filtered water that is available off-the-grid. While there are a number of different options you can consider, this particular post discusses the gravity feed water filter.  This type of system is useful when you need to supply clean water to a small group of people, as, for example, family members.

What is a Gravity Feed Water Filter System?

The principle of operation of a gravity feed water filter system is straightforward enough.   The system consists of two main chambers, an upper chamber and a lower chamber, and a channel (or set of channels) between containing the filter media.   Dirty water is placed into the upper chamber and the force of gravity overcomes the resistance presented by the filter media, causing the filtered water to flow into the lower chamber which can be accessed via a spigot.  The larger the area the filter presents between the two chambers (eg, using multiple filters working in parallel), the faster the flow rate should be, but obviously, the more expensive the unit is to operate.

Some individuals decide to make their own gravity feed water system, for example, by stacking two 5 gallon buckets and then interposing a filter in between.   You can choose to use a microporous-ceramic dome filter filled with activated carbon as the interposing filtered media or you could choose to use two to four candle type filters instead.   There are websites which describe how to build your own gravity filtration unit, such as this one.

Considerations When Purchasing a Gravity Feed Water System

If you instead to decide to purchase your own unit, note the following considerations:

  • Water Quality: The unit you plan to buy should be able to operate under normal conditions but should also be usable during civil emergencies.  This means the filter/purifier should be able to work equally well with pre-filtered water taken from the tap to water coming from lakes, ponds or streams.  Note that there is an important distinction between filter and purifier.   Purification sets a higher standard (is, in fact, the highest standard) for water filtration.  While a filter is set to improve water’s smell and taste and will remove such elements as toxic chemicals, heavy metals, herbicides, trihalomethanes, volatile organic compounds (VOCs), pesticides, pharmaceutical contaminants, as well as some bacteria, a purifier will do so at a higher degree and will also eliminate most bacteria and viruses.   If you are filtering pre-filtered water from the tap under normal conditions, a standard filter may be suitable for your needs.  If, on the other hand, you are filtering raw untreated water as from ponds, lakes, and streams, a purifier would be recommended.   The higher standard of the purification unit obviously comes with a higher price tag.

  Note that some manufacturers offer activated alumina filters for eliminating toxins such as fluoride and arsenic from your purified water,     so you may want to inquire about these.

  • Capacity: You want a unit that is large enough to handle the number of people it will serve at any one time.  According to the National Academies of Sciences, Engineering, and Medicine, you should drink about 15.5 cups (3.7 liters) of water a day if you are an adult male and about 11.5 cups (2.7 liters) of water a day if you are a woman.  Note that these values consist of intake from water and other beverages as well as from food,   Approximately 20% fluid intake comes from food, so we will assume 80% of these values is what is needed for pure fluid intake.

  Let’s say you are a family of 5, and to be conservative, we will simply use the value for adult males to cover both women and children, even     though their needs are less.  So we can calculate the amount of water intake of the family on a daily basis as (noting that there are   16 cups   per  gallon):

Total Requirement = 5 * 0.8 * 15.5 cups * 1 gal/16 cups = 3.875 gallons (or 4 gallons approximately).

If you consider that you also need clean water to cook, wash dishes, for personal hygiene as well as other things, you should adjust the figure accordingly to support these activities.   A calculator for giving a more realistic idea for the specifics about your family can be found here.

  • Filtration Speed: Some units you come across may have very slow filtration rates, and so you should be aware of these specifications when you are shopping around for a gravity feed water filter system.  You don’t want to have to wait 10 minutes or longer for the lower chamber to start filling.  Filtration flow rate is typically listed in a number of gallons per hour.  For example, the Big Berkey advertises a maximum filtration flow rate of two Black Berkey Purification Elements of up to 3.5 gallons per hour.   Flow rates may decrease with prolonged use and may be an indicator that filters need cleaning.



In this day and age, it is best to be prepared for the uncertainty that life brings.  And while this statement may seem alarmist, I am positive that if you asked any of the people whose lives had been impacted by the devastation of natural disasters, they would certainly agree.  Water security should be at the top of your list of preparedness items you will want to consider.   In future posts, I will be reviewing some of the more of the more popular gravity feed water filter solutions as well as more portable options should you need to bug out.

Until next time…







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