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Water Contamination and The Gravity Fed Water Filter

In the United States, we often take for granted the abundance of available freshwater supplies. Natural disasters, terrorist attacks, or widespread biological contamination could destroy our groundwater supply overnight.

What once was a productive well or a fresh mountain stream could easily become a haven for various contaminants with potentially lethal consequences.

What we need is a solution for water purification that is sustainable. Commercially available filters and chemical purification methods work well but we cannot guarantee their availability indefinitely.

First, let’s take a look at some common water contaminants. Understanding what we are up against helps to demonstrate just how important proper water purification is.

After we have discussed these dangers, we will look at a sustainable water filtration system that can be constructed at home very inexpensively and is capable of removing most, if not all, contaminants from the water supply

There are thousands of contaminants that can easily find their way into our water supplies. When we turn on the faucet in our home, we assume that the water treatment facility has successfully removed any contamination from the water.

If we have a well, we assume that the groundwater is safe for consumption.

For the most part, these water sources are safe. However, water supplies can quickly become contaminated or even cease to exist altogether.

We need to understand the nature of some of these contaminants to better understand exactly how important water purification is in a sustainable lifestyle.

Heavy Metals

Heavy metals such as mercury and lead can find their way into natural water sources and pose a serious threat to humans.

Usually, there is no way to tell if heavy metals have contaminated the water supply without specialized water testing equipment.

Some of the effects of heavy metal poisoning include:

  • stunted growth and development
  • cancer
  • organ damage
  • nervous system damage
  • autoimmune disease
  • death

Heavy metals that are commonly associated with human poisoning include lead, arsenic and cadmium.

Copper, zinc and chromium can also make their way into the water supply. Although these elements are naturally found in the body in small amounts, larger amounts are considered to be toxic.

Mercury and lead are known to cause the development of autoimmunity (where a person’s immune system attacks its own cells) which can lead to joint diseases such as rheumatoid arthritis as well as diseases of the kidneys, circulatory system and nervous system.


Turbidity is a measurement used to describe the loss of transparency in water due to the presence of foreign matter.

A higher turbidity level means that there are more suspended solids in the water. These solids make the water appear murky

Turbidity can be caused by erosion sediment, algae growth, urban runoff, and waste discharge.

The sediments that create turbidity can also promote higher levels of heavy metals and toxic organic compounds which tend to attach themselves to the suspended particles.

It’s important to note that turbidity is not an indication of contaminated water by itself. A higher turbidity level definitely increases the likelihood that pathogens are in the water, but this is not always the case.

Organic Compounds

Pesticides, herbicides, and even gasoline are all considered organic compounds. The presence of these compounds cannot be confirmed in most cases without testing equipment.

These compounds are sometimes referred to as VOCs, which stands for volatile organic compounds. A VOC has specific chemical properties including:

They evaporate, or vaporize, quickly

They contain carbon

The EPA estimates that VOCs are present in one-fifth of the nation’s water supplies. Exposure to high levels of VOCs causes central nervous system depression and irritation upon contact with the skin and mucous membranes.

Most organic compounds are introduced into the water supply by runoff from farms, industrial centers, and urban areas. Although these contaminants can enter the groundwater supply, they are more typically found in surface water.


Pathogens refer to a variety of bacteria, viruses, protozoan parasites, and other organisms. Some of the most common pathogens include:

Cryptosporidium – Cryptosporidium is a protozoan parasite found in lakes and rivers, especially when the water has been contaminated with sewage or animal waste. The parasite causes gastrointestinal problems including diarrhea, vomiting and severe stomach cramps.

Giardia lamblia – Giardia is another protozoan parasite that resides in the intestines of humans and animals. It is found in water that has been contaminated with feces from infected humans or animals. Symptoms typically include nausea, cramps, diarrhea and headaches.

Legionella – Legionella bacteria are found naturally in the environment. The bacteria only become a health risk to humans when the water becomes aerosolized such as in an air-conditioning system or a shower. Once inhaled, there is a risk of contracting a type of pneumonia known as Legionnaire’s disease.

Viruses – Enteroviruses also live in the intestines and includes the poliovirus, coxsackievirus, echovirus, and other enteroviruses. Illnesses from these viruses vary depending on the species but range from gastroenteritis to meningitis.

Bacteria are also responsible for diseases such as typhoid fever, cholera, chronic diarrhea, and dysentery.

E. coli can also be contracted through contaminated water supplies. In healthy people, E. coli typically only creates mild discomfort although people with weakened immune systems can suffer more serious symptoms including fatal reactions.

Biological and/or Chemical Attack

Another serious threat in the United States comes from the possibility of terrorist attacks. Many foiled attacks in the past have focused on intentionally adding biological or chemical contaminants to public water supplies.

Most water treatment facilities do have security measures in place to prevent against unauthorized entry and contamination; however, the threat is still present and could be devastating to large populations in a short period of time.

This is just a small sample of the many thousands of contaminants that can be introduced into our water supplies. In the next section, we will look at some common diseases contracted from waterborne pathogens.

Common Waterborne Diseases

There are many diseases that can be contracted from consuming contaminated water. Let’s take a look at a few of the common illnesses associated with waterborne pathogens.

Dysentery causes severe diarrhea that can lead to dehydration, shock, and possibly even death. It is caused by a variety of bacteria including Shigella and E. coli. An amoeba known as Entamoeba histolytica is also known to cause dysentery.

These organisms can all be found in the feces of people and animals. When infected fecal matter is introduced to the water supply and consumed, these bacteria colonize the intestinal tract and symptoms usually begin within a few days.

Even though most of us have been vaccinated against cholera and typhoid, you can still become infected by drinking contaminated water.

Cholera is an acute bacterial infection of the intestinal tract. The severe diarrhea caused by cholera can lead to dehydration and possibly even death if left untreated.

Typhoid, or typhoid fever, is caused by the salmonella typhi bacteria. High fever, sweating, and diarrhea are all symptoms of this illness.

There are also quite a few parasitic insects that are dangerous to humans one consumed. Douves is a parasitic worm that makes its home in the liver. It can be found in stagnant water in tropical climates.

These parasites can enter the body through consumption of contaminated water or even penetrate through the skin.

Small leeches can also be ingested and cause wounds that are painful and prone to infection.

Guinea worm disease, also known as Dracunculiasis, is contracted by drinking water contaminated with Dracunculus larvae. These larvae grow into large worms (3 m in some cases) and cause debilitating ulcers in the intestinal tract.

The risk from long-term exposure to certain chemicals is also significant. Arsenicosis stems from repeated exposure to arsenic in drinking water. Symptoms may include painful lesions on the skin and possible cancer of the lungs, bladder, and kidneys.

This list is not meant to be all-inclusive. There are numerous other dangers associated with contaminated drinking water.

We have gone over some of the more common ones simply to make sure you are aware of how important water purification is now and in the future.

The Gravity Fed Water Filter

Before we dive into constructing our own gravity fed water filter, let’s quickly take a look at how these systems work, why they are effective, and why it is one of the most sustainable water filtration solutions available.

As the name implies, gravity fed filters rely on the force of gravity to pull water through the filter element and into a catch basin below.

Commercially manufactured models usually come as one unit with two different tanks for holding water. Our design is much simpler and just as effective, at a much lower cost.

The filter is made up primarily of ceramic with additives to prevent microbial growth within the filter element itself.

There are quite a few manufacturers of ceramic filters in each has different replacement intervals and flow rates. For the purposes of our gravity fed filter, we will be relying on a Doulton 7”Ceramic Filter.

Typically, these filters have a filtration rating of around 0.9 μ absolute. This means they are able to filter out even the smallest of bacteria and other pathogens.

According to Doulton, this filter removes 99.99% of bacteria including E. coli, cholera, Shigella, typhoid, and many others. It also removes 99.99% of cysts such as Cryptosporidium and Giardia.

Chlorine and VOCs are reduced by 95% or more. The filters also reduce turbidity by 98%.

This means that our water filter is capable of removing just about any possible contaminant from water supplies with relative ease.

To keep costs low, we are looking at one of the less expensive ceramic filters.

It is rated for approximately 535 gallons of filtered water before needing replacement. This figure will vary depending on how contaminated your water supply is but as a general rule, they require replacement every 6 to 9 months regardless of usage.

Keep in mind that the ceramic material can be gently cleaned with a soft tooth brush and clean water. This exposes a new layer of fresh ceramic and will greatly extend the life of your filter.

If you decide to clean your filter, a soft scouring pad can also be used. Make sure you always scrub away from the threaded mount so it doesn’t become contaminated. Never use soap, detergent, or steel wool during cleaning.

You may be wondering why we are focusing on creating a filtered water system after mentioning some of the challenges they present for long-term sustainability.

The answer is simple – no other filtration method can remove heavy metals, pathogens, and VOCs as reliably as a ceramic filtration system.

The design we are looking at can process much more water and the filters are inexpensive enough that stocking a decent supply of them can be done without spending too much money.

Maybe you can’t store enough filters to last a lifetime, but you can certainly rely on your gravity fed system for a few years before having to worry about another purification solution.

Also keep in mind that the life of the filter depends significantly on the pollution level of the water. During long term situations, try to use rain water or other sources that tend to have less contamination to extend the lifecycle of your filter as much as possible.

Constructing the Filtration System

The Water Filter

Now that we understand the basics of how gravity fed filtration systems work, let’s go over the process of constructing one at home.

This project is very simple and can be completed in less than an hour without the need for any special skills.

If you are uncomfortable making this filter DIY, similar designs can be purchased but expect to pay as much as 400% more for a ready to use model.

The materials we need include:

Ceramic 7” Candle Filter – Two of the most popular manufacturers are Doulton and Berkey. Filters from either of these companies can be used, but we will be using the Doulton 7” SuperSterasyl Ceramic Filter for this project. Although this model does not filter as many gallons of water as some of the Berkey filters available, it is more affordable and can always be swapped out for a higher-end model in the future.

(2) 5 Gallon Buckets – These buckets should be made of food grade plastic such as HDPE. This plastic will not add harmful chemicals such as BPAs to your purified water. These can often be purchased at local retailers or sourced online.

(2) Bucket Lids – Make sure to get lids designed for use with the particular brand of bucket you purchase to ensure a proper seal.

Replacement Drain Cock – These are sold for a variety of water containers and coolers. Pretty much any of them will work as long as it has a gasket and wing nut to secure it inside the bucket.

Food Grade Silicone Seal – The sealant is used to seal the gap between the two buckets. Although using sealant is not essential, it ensures that no contaminants inadvertently end up in the purified water and helps to keep the system together.

Electric Drill – A drill is required to make a 1/2” hole to accommodate the filter.

Hole Saw – The saw is used to cut circular a hole large enough to accommodate the wing nut on the bottom of the filter element.

That’s it! This list represents everything we need to construct our $50 gravity fed water filter. Let’s go step-by-step through the construction process.

Drill a pilot hole in the center of one of the bucket lids (or evenly spaced if installing multiple filters). Using the hole saw, enlarge the pilot hole into a 1 .” diameter circle. If you don’t have a hole saw, you can also use a drill attachment designed for installing door locks. These attachments can be purchased inexpensively at home improvement stores. This hole is necessary to accommodate the wing nut on the bottom of the filter.

Step 2

Attach this lid to the bottom of a bucket using silicone sealant. This bucket will become the top bucket where contaminated water is held. Use two beads of sealant – one in the recess around the inside of the lid to seal the bottom of the bucket to the lid and the other around the bottom of the bucket just above the lid to prevent contaminated water from seeping into the clean water supply. Allow the sealant to dry thoroughly before continuing.

With your electric drill and .” drill bit, drill a hole in the bottom of the top bucket. The easiest way to do this is to guide the drill bit through the larger hole you created in the attached lid. This ensures that both holes lineup properly. Make sure the hole is exactly .” to accommodate the threaded stem of the candle filter. Failure to do this could result in leaks and contamination of the “purified” water in the bottom bucket.

Mount the filter from the top of the bucket. The filter comes with a wing nut and a gasket, both of which are required for proper operation. The gasket goes inside the bucket, directly below the filter element. The wing nut is attached from the bottom through the larger hole you cut in the lid.

Step 3

Drill a small hole near the bottom of the second bucket for the drain cock. The size of this hole will vary depending on the replacement drain cock you purchase. Make sure it is a snug fit and the gasket is installed properly so purified water does not leak out.

Place the top bucket onto the bottom bucket ensuring that the lid of the bottom bucket is secured. The silicone sealant we installed earlier holds the lid and top bucket together making for a sturdy structure that will not leak.

Make sure to clean out any plastic shavings from the construction process before using your gravity fed filtration system.

With our water filter complete, it is now ready for use and you can begin filtering water immediately. The length of time it takes to filter 5 gallons of water depends on the exact filter model you chose for this project.

The Doulton model we used in this example filters water at the rate of approximately 1 L per hour. This means about 10 gallons can be run through the filter in a 24-hour period.

As a side note, these filters can be used in many configurations without modifying the design too much.

For instance, our filter system could have double the amount of ceramic filters. This would filter water twice as fast and extend the life of the filtration system.

Finished filter

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