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Types of Water Contaminants & How to Make Water Safe

Water Purification

We must be ready to treat unsafe water from our home faucets and non-potable water from outside sources when needed. Preparing for these two possibilities will help shore up our water supply if we know how to successfully treat undrinkable water. To do this, we must first be able to identify the pathogens and chemical compounds we are dealing with.

The Safe Drinking Water Act defines a "contaminant" as any physical, chemical, biological, or radiological substance or matter in water. Most contaminants cause harm when ingested rather than absorbed.

Water Purification
General Categories of Drinking Water Contaminants

Physical

Physical contaminants affect the appearance and physical properties of water. They may make water look cloudy, dirty, or unappealing, but they typically do not cause harm if swallowed. Common examples include sediment, sand, silt, rust, and organic debris suspended in water from lakes, rivers, and streams.

Effective
Sediment filters: 20 to 50-micron
Remove sand, rust flakes, and visible sediment - often used as a first‑stage “pre‑filter". Does not remove microbes or chemicals.
Sediment filters: 5-micron
Remove fine sediment, silt, rust, turbidity, and organic debris - extremely common as a general sediment filter or “pre‑filter" stage. Is not a microbiological barrier.
Sediment filters: 1-micron Absolute
Remove very fine sediment and turbidity - can help reduce larger cysts/parasites, but not a full microbiological barrier.
Note: “Absolute” rating is required; “nominal” 1‑micron filters do not reliably remove cysts.
Not Effective
Boiling
kills microbes but concentrates sediment
UV systems
kill microbes but do not remove particles
Chemical Disinfection
Includes chlorine, chlorine dioxide, iodine and pool shock - they do not remove particles
Activated carbon
improves taste/odor but does not remove sediment
Ceramic filters
remove microbes but do not remove sediment or turbidity
Reverse osmosis membranes alone
require a sediment pre‑filter to avoid clogging and are not designed for particle removal
Learn more about sediment filters

Chemical

Chemical contaminants can be naturally occurring or man‑made. Natural contaminants may enter water through runoff, erosion, geological minerals, or biological processes. Man‑made contaminants often come from industrial releases, spills, improper waste disposal, agricultural chemicals, or corrosion of metal pipes and infrastructure.

Effective
Distillation
Distillation removes nearly all forms of chemical contaminants, including salts, heavy metals, nitrates, fluoride, and many organic compounds. It works by vaporizing water and leaving contaminants behind.
Nanofiltration (0.001-micron)
Moderately effective: removes many organic compounds, some pesticides, some dissolved salts, and some heavy metals - it is less effective than RO for small ions and does not reliably remove all chemical contaminants.
Reverse Osmosis (0.0001-micron)
Reverse osmosis is one of the most effective household methods for removing dissolved chemicals. Effectiveness varies by membrane quality, pressure, and system design. Highly effective against: sodium, chloride, copper, chromium, and lead.
Moderately effective against: arsenic fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous.
Not Effective
Boiling
Boiling kills biological pathogens but does not remove chemicals - it can increase chemical concentration by evaporating water and leaving contaminants behind.
Ultraviolet (UV) Systems
UV light inactivates microbes but has no effect on dissolved chemicals, metals, salts, or organic compounds.
Solar Disinfection (SODIS)
Uses sunlight to inactivate pathogens - does not remove or reduce chemical contaminants.
Chemical Disinfectants
Includes chlorine, chlorine dioxide, iodine and pool shock -these kill bacteria and viruses but do not remove chemicals already present in the water - may even add chemical byproducts.
Mechanical Filters (0.01 micron and larger)
Sediment filters, ceramic filters, microfiltration, and ultrafiltration remove particles, not dissolved chemicals - chemical contaminants are far smaller than the pore size and pass through freely.
Learn more about these treatment methods

Biological

Biological contaminants are living microorganisms that can cause illness when present in drinking water. These include viruses, bacteria, and parasites, all of which are invisible to the naked eye. Even tiny amounts can lead to severe gastrointestinal disease. Common examples include E. coli, Salmonella, Vibrio cholerae, typhoid bacteria, Giardia, Cryptosporidium, and various parasitic worms. Because biological contaminants vary dramatically in size, different treatment methods are required to remove or inactivate them.

Effective against parasites, bacteria, and viruses
Boiling
Inactivates all biological pathogens when water reaches a rolling boil.
Distillation
Kills or removes all biological contaminants through vaporization and condensation.
Ultraviolet (UV) Disinfection
Inactivates parasites, bacteria, and viruses when properly dosed and water is clear.
Solar Disinfection (SODIS)
Uses UV A and heat from sunlight to inactivate pathogens; effectiveness depends on sunlight intensity and exposure time.
Nanofiltration: (0.001-micron)
Removes parasites and bacteria; may remove some viruses, but virus removal is not fully reliable and depends on membrane design.
Reverse Osmosis (0.0001-micron)
Removes nearly all parasites, bacteria, and most viruses through extremely fine membrane filtration.
Effective against parasites and bacteria (but not viruses)
Ultrafiltration (0.01-micron)
Removes parasites, bacteria, and some viruses though not reliably.
Effective against parasites Only
1 Micron Absolute Filters
Removes larger parasites and cysts - does not remove bacteria or viruses.
Microfiltration (0.1 micron)
Removes parasites (Giardia, Cryptosporidium); partial removal of bacteria - does not remove viruses.
Effective against bacteria and viruses (but not parasites)
Chemical Disinfection
Includes chlorine, chlorine dioxide, iodine, and pool shock - Removes bacteria and viruses; not effective against parasites such as Giardia and Cryptosporidium - must be paired with a 1 micron absolute filter if parasites are a concern.
Learn more about these treatment methods

Radiological

Radiological contaminants in drinking water can occur naturally or from human activities. Naturally occurring radioactive materials (NORM) such as uranium, radium, and radon dissolve into groundwater as it moves through certain rock and soil formations. These elements and their decay products can pose long term health risks, including increased cancer risk and kidney damage when consumed over time. Man made radiological contaminants may enter water supplies through improper disposal of radioactive waste, industrial activities, or nuclear incidents.

Distillation
Distillation can remove most radiological contaminants by separating water vapor from dissolved radioactive solids.
Reverse Osmosis (0.0001-micron)
Reverse osmosis is one of the most effective household scale methods for removing many radioactive contaminants, including uranium and radium, through extremely fine membrane filtration.
Ion-Exchange Resins
Ion-exchange systems can remove radium and uranium by swapping radioactive ions with harmless ions on the resin surface. Many municipal systems use ion-exchange as a primary treatment for radionuclides.
Adsorptive Media
Certain adsorptive media (e.g., activated alumina, specialized media) can remove uranium and other radionuclides by binding them to the media surface.
Important Notes
No single treatment method removes all radionuclides equally well. Effectiveness depends on the specific isotope, water chemistry, and system design. Radiological contamination is typically a long term exposure risk, not an immediate acute hazard. Testing is essential if you live in an area with known uranium or radium in groundwater.
Learn more about these treatment methods
Water Purification
Water Purification Steps

Signs of Unsafe Water

Contaminated water often has a bad odor, unpleasant taste, and can sometimes appear cloudy or discolored. It may contain microorganisms such as bacteria, viruses, or parasites that can cause serious health issues like dysentery, typhoid, cholera, hepatitis, and other illnesses. In some cases, harmful chemicals or heavy metals might also be present, further compromising water safety.

Treating Water Contamination

If your water source is of uncertain quality, it’s essential to purify it before use to protect your health. This includes any water intended for drinking, dishwashing, oral hygiene, food preparation, or making baby formula.

Purification typically involves a two-step process: first, removal of visible debris and sediment using filtration; then, elimination of pathogens through boiling, chemical treatment, or other water purification systems.

Step 1: Debris Removal

Debris removal filters out contaminants that cause water to appear dirty or cloudy. While you can use a paper towel or coffee filter in a pinch, using a proper water filter is recommended. (Learn more below.)

Step 2: Pathogen Elimination

Pathogens like protozoa, bacteria, and viruses must be removed or killed. Some methods can kill all three at one time, while others need to be used together to successfully purify the infected water. (Learn more below.)

Water Purification
Debris Removal

Sediment Filtration

Sediment filtration removes physical particles from water by straining them through filters with different pore sizes, measured in microns. Any contaminant larger than the pore size is trapped, while smaller particles pass through.

Sediment filters come in several common sizes, each serving a different purpose:

  • 20–50-micron filters - Capture large debris such as sand, rust flakes, and visible sediment. These are often used as the first stage to protect finer filters from clogging.
  • 5-micron filters - Capture fine sediment, silt, rust, and turbidity. This is one of the most common general purpose sediment filters and is typically used after a coarse pre filter.
  • 1-micron absolute filters - Capture very fine sediment and can help reduce larger cysts/parasites. These provide the finest level of mechanical filtration but are not a full microbiological barrier.

Sediment filtration improves clarity and protects downstream filters, but it does not remove bacteria, viruses, chemicals, or dissolved contaminants. Many harmful contaminants are far smaller than even a 1-micron filter, so once sediment has been removed, additional treatment (such as membrane filtration or chemical treatment media) is needed if those contaminants are present.

Water Purification
Pathogen Elimination

Click on each method to learn more.

Boiling Water

Boiling is the surest method to kill disease-causing germs, including viruses, bacteria, and parasites. It is seen as the safest method of treating water because you are not adding chemicals into the water during the process, as most other methods do. It is ineffective at removing toxins. While boiling kills biological pathogens, it does not remove chemicals or physical debris. In fact, it can even concentrate chemical contaminants by evaporating water.

Directions

In a large pot or kettle:

  • Bring clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for 3 minutes).
  • Be aware that some water will evaporate.
  • Allow the water to cool before drinking.

Tips for better tasting water

Boiled water can taste better by doing one of the following:

  • Pour the water back and forth between two clean containers, then allow it to stand for a few hours. This aerates the water and improves taste.
  • Add a pinch of salt per quart or liter of boiled water.

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Chemical Disinfection

Chemical disinfectants such as bleach, chlorine dioxide, and iodine are effective at killing viruses and bacteria, as well as the giardia parasite. Note that these disinfectants are generally not effective against Cryptosporidium. They do not remove chemicals, heavy metals, sediment, or organic debris. They may also create chemical byproducts.

Popular chemical disinfectants include bleach, chlorine dioxide (in tablet form), iodine (available as a 2% liquid solution or in tablet form), and Pool Shock (as an alternative, used only if standard bleach is unavailable). (See below for details.)

Chlorine Bleach

Unscented liquid chlorine bleach in the United States typically contains 6% to 8.25% sodium hypochlorite. Always read the label to determine the concentration and adjust the dosage accordingly.

Directions

  • Select a measuring device (dropper, mL syringe, or teaspoon set).
  • Add the appropriate amount of bleach to your water – see mixing amounts below.
  • Stir thoroughly.
  • Allow the mixture to stand for at least 30 minutes before drinking.
  • Store the disinfected water in clean, sanitized containers with tight covers.

Mixing Amounts

6.25% to 8.25% Sodium Hypochlorite
Per quart or liter
  • - Add 2 drops (≈0.1 mL)*
Per 1 gallon
  • - Add 8 drops (≈0.5 mL or 1/8 tsp)
Per 5 gallons
  • - Add 40 drops (≈2.5 mL or 1/2 tsp)
* too small to measure
1% Sodium Hypochlorite
Per quart or liter
  • - Add 10 drops (≈0.5 mL or 1/8 tsp)
Per 1 gallon
  • - Add 40 drops (≈2.5 mL or 1/2 tsp)
Per 5 gallons
  • - Add 200 drops (≈12.5 mL or 2.5 tsp)
Tip

For easier measuring follow these tips:

  • Avoid using a teaspoon for small volumes; use a more precise measuring method.
  • Keep your measuring device with your bleach supply.

DOWNLOAD INSTRUCTIONS
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Chlorine Dioxide

Chlorine Dioxide is a chemical compound used in public water-treatment facilities to make water safe for drinking. It is not the same thing as chlorine bleach though it can produce some of the same results.

Comes in tablet form

Typically, one tablet can purify 1-2 liters of water in 30 minutes.

PROS
  • Fast acting
  • Popular method for on-the-go water disinfection.
  • Convenient pre-portioned tablets that are easy and safe to use (follow package instructions).
  • No unpleasant taste or odor.

Shelf life: 4 years from manufacture.

Iodine

Iodine, available as a 2% liquid solution or in tablet form, is moderately effective as a disinfectant.

Liquid 2% Solution

Add five drops per quart or liter; if water is cloudy, add 10 drops. Stir and let stand for 30 minutes.

Tablet Form

One tablet can purify 1-2 liters of water in 30 minutes.

PROS
  • The least expensive tablet option compared to chlorine dioxide.
CONS
  • Unpleasant taste (consider adding a powdered drink mix).
  • Not recommended for pregnant women, individuals with thyroid issues, or those allergic to iodine.
  • Not recommended for continuous use beyond a few weeks.

Shelf life: 4 years from manufacture.

Pool Shock

Pool shock is a chlorine-based product used for swimming pools. It can also be used to disinfect water if used correctly. It is a strong chemical and should only be used if your bleach has expired. Unlike bleach (which expires after 6–12 months), pool shock has an almost indefinite shelf life when stored properly. A 1-pound bag can disinfect up to 10,000 gallons. You can see why it’s a smart move to store this product with your other water purification supplies. If you run out of the other, this makes a great backup.

source: HTH

What to look for

Purchase pool shock containing 68% or higher Calcium Hypochlorite. Examples include: HTH Ultimate–Shock Treatment 7 in 1 and Ultima TKO. Remember, use it only as a backup option and follow all safety instructions.

DOWNLOAD INSTRUCTIONS
- place with your storage materials -

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Filtering of Pathogens

Different types of filters are designed to remove various contaminants, including viruses, bacteria, parasites, heavy metals, pesticides, and herbicides. However, the specific effectiveness depends on the filtration method and pore size, also known as the micron rating.

Before looking at the filtration table, it helps to understand that filters fall into three broad categories.

Mechanical Filters

These work like a sieve, physically straining out particles such as sediment, rust, silt, turbidity, and some larger microorganisms like parasites and some bacteria. They improve clarity and protect downstream filters but do not remove chemicals or viruses.

Filters include:

  • 20–50 micron sediment filters
  • 5 micron sediment filters
  • 1 micron absolute filters
  • 0.2-0.5 micron ceramic filters
Membrane Filters

These use extremely fine pores to block much smaller contaminants. Depending on the pore size, they can remove bacteria, parasites, some or most viruses, and even dissolved chemicals. They provide much higher contaminant removal but often require pressure and slower flow rates.

Filters include:

  • microfiltration - 0.1 micron
  • ultrafiltration - 0.01 micron
  • nanofiltration - 0.001 micron
  • reverse osmosis - 0.0001 micron
Chemical Treatment Media

These do not rely on pore size at all. Instead, they remove contaminants through chemical reactions. These methods do not remove microbes or sediments and are often paired with mechanical or membrane filters.

They include:

  • Activated carbon removes chlorine, VOCs, pesticides, herbicides, and many organic chemicals through adsorption.
  • Ion-exchange resins remove hardness minerals and some heavy metals by swapping ions in the water.

Combining Methods

No single filter removes everything. Combining filtration methods provides the best protection. For emergency preparedness, it’s smart to have a reliable multi stage system or a combination of filters on hand.

Filtration Methods & Micron Ratings

Filtration Method Micron Rating Contaminants Removed Limitations
Sediment Filtration 1-50 micron Removes sediment, rust, silt Does not remove microbes or chemicals
Sediment Filtration 1 micron (absolute) Removes parasites Not effective against bacteria or viruses; not full pathogen removal
Ceramic Filtration 0.2–0.5 micron (absolute) Removes bacteria, parasites, cysts; reduces turbidity Not effective against viruses or chemicals; flow rate slows as pores clog; requires regular cleaning
Microfiltration 0.1 micron Most bacteria, parasites Viruses not removed
Ultrafiltration 0.01 micron Bacteria, parasites, some viruses Some small viruses may pass through
Nanofiltration 0.001 micron Bacteria, parasites, many organic compounds, some dissolved salts Removes some viruses - but not reliably
Reverse Osmosis (RO) 0.0001 micron Wide range: chemical contaminants, heavy metals, bacteria, parasites, nearly all viruses Slow process, requires water pressure, produces wastewater
Activated Carbon N/A - Chemical Adsorption Removes chlorine, VOCs, many pesticides/herbicides Does not remove bacteria, parasites, or viruses
Ion‑Exchange Resins N/A - Ion-Exchange (Chemical Process) Remove hardness minerals and some heavy metals but effectiveness depends on resin type Does not remove bacteria, parasites, or viruses
Sediment Filter - 1-50 micron

Removes sediment, rust, silt, organic debris - does not remove microbes or chemicals

Sediment Filter - 1 micron (absolute)

Removes parasites - is not effective against bacteria or viruses; not full pathogen removal

Ceramic Filter - 0.2–0.5 micron (absolute)

Removes bacteria, parasites, cysts; reduces turbidity - does not remove viruses or chemicals; flow rate slows as pores clog; requires regular cleaning

Microfiltration - 0.1 micron

Removes most bacteria and parasites - does not remove viruses

Ultrafiltration - 0.01 micron

Removes bacteria, parasites, and some viruses - some small viruses may pass through

Nanofiltration - 0.001 micron

Removes bacteria, parasites, many organic compounds and some dissolved salts - removes some viruses but not reliably

Reverse Osmosis - 0.0001 micron

Removes chemical contaminants, heavy metals, bacteria, parasites, and nearly all viruses. Though this is one of the most comprehensive filtration methods, keep in mind that it is a slow process, it requires water pressure, and produces wastewater.

Activated Carbon Filter

Removes chlorine, VOCs, many pesticides/herbicides - does not remove bacteria, parasites, or viruses

Ion‑Exchange Resins

Ion‑exchange resins remove hardness minerals and some heavy metals; effectiveness depends on resin type - does not remove bacteria, parasites, or viruses

Note: Filtration effectiveness varies by specific product design and maintenance. Be sure to always follow manufacturer guidance for safe water treatment.

Certified Filters

Testing

While the water filter industry is not regulated, strict health standards for drinking water have been put forth by the National Sanitation Foundation (NSF) and the American National Standards Institute (ANSI). Tests are conducted by accredited third parties against these high standards and are offered to any filtration company willing to pay. Filters that pass are given a certificate, ensuring consumers that the water filter they're buying meets the highest standards. Meaning, it can remove or reduce Crypto.

Certified Filters

To see which filters have received certification, look for one of the following the on-product labeling and the company's marketing materials.

  • Reverse Osmosis (with or without NSF 53 or NSF 58)
  • Tested and certified to NSF/ANSI Standard 53 or NSF/ANSI Standard 58 for cyst removal
  • Tested and certified to NSF/ANSI Standard 53 or NSF/ANSI Standard 58 for cyst reduction
Non-Certified Filters

Because testing to ANSI standards is very expensive and voluntary, some filtration companies simply won’t pay. That does not mean their filters are not good. These companies run their own tests and have documentation on what their filters can and cannot do. They just can't prove it with a testing certification. Before you purchase a filter from an uncertified source, read their documentation closely.

Be wary of the following labeling

There are many filters on the market that just don't do the job and take advantage of the consumer who does not know what to look for. Per the CDC, filters labeled with the following words may NOT be designed to remove Cryptosporidium (Crypto) and other dangerous pathogens.

  • - Nominal pore size of 1 micron or smaller
  • - One micron filter
  • - Effective against Giardia
  • - Effective against parasites
  • - Carbon filter
  • - Water purifier
  • - EPA approved (EPA does not approve or test filters)
  • - EPA registered (EPA does not register filters)
  • - Activated carbon
  • - Removes chlorine
  • - Ultraviolet light
  • - Pentaiodide resins
  • - Water softener
  • - Chlorinated
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Solar Disinfection (SODIS)

Solar Water Disinfection, also referred to as SODIS is a type of portable water purification system that uses solar energy to kill biological contaminants, namely viruses, bacteria, some parasites like Giardia, and worms. It is not effective against the more stubborn Cryptosporidium and does not remove chemicals or physical contaminants.

After enough exposure, the sun’s UV rays ultimately alter the DNA molecules of pathogens in the water. A process of photo-oxidation then destroys the microbes, preventing sickness and disease.

While it does destroy, it does not remove pathogens. If you would like to have that done, using a 1-micron filter can do that. Water contaminated with non-biological agents such as toxic chemicals or heavy metals requires other purification methods to make the water safe to drink as SODIS will not remove any other type of contamination.

Source: Wikipedia

Solar purification steps

  • #1 If necessary, filter the water to make it as clear as possible.
  • #2 Use PET plastic or glass bottles (a 2-liter soda bottle is acceptable).
  • #3 Ensure bottles are in good condition, washed, colorless, transparent, and free of labels.
  • #4 Fill the bottles with water and close the cap.
  • #5 Shake the bottles thoroughly to mix in oxygen.
  • #6 Expose the bottles to direct sunlight for at least 6 hours (or 2 full days under cloudy conditions).
  • #7 Store the water in the treated bottles until ready for use to minimize contamination risks.
  • #8 When needed, drink directly from the bottle or from a clean cup.

PROS
  • Relatively easy and inexpensive using readily available materials.
CONS
  • Requires 6 hours to 2 days of sunlight, limiting immediate availability.
  • Only inactivates biological contaminants—not chemical or radiological ones.

DOWNLOAD INSTRUCTIONS
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Ultraviolet (UV) Disinfection

Ultraviolet (UV) Treatment uses ultraviolet light to disinfect water and is effective against viruses, bacteria, and all parasites. High-dosage lamps are highly effective at treating these pathogens and differ from the other disinfectant methods in that the process is chemical-free. It is not a standalone method as it must be used with a pre-filtration system. The UV system is most effective when the water is clear and free of physical contaminants. The use of at least a 5-micron filter is sufficient. It does not remove dissolved chemicals, heavy metals, salts, pesticides, sediment or turbidity. Here's how the UV treatment works.

source: puritor.com

UV process

Contaminated water is exposed to germicidal ultraviolet light. The UV wavelength damages the DNA of living organisms, making them unable to reproduce which is what will make you sick. The higher the UV dosage, the more energy is delivered to treat contaminated water. Energy needs to reach a certain threshold to be sufficient to inactivate most microorganisms in the water.

While UV treatment purifies water by exposing living organisms to ultraviolet light, it does not filter them out. If you want to filter out the microorganisms themselves, an additional 1-micron filter is sufficient. (Don’t use this filter for pre-filtering as this can clog this smaller pore-sized filter.) UV systems are often paired with Reverse Osmosis Systems as well, to provide a complete purification process for the safest drinking water.

source: prathamfilter.in
UV System

Here's a simple look at the unit itself.

  • 1. An outer chamber encases the UV unit and is held together by 1 or 2 O-rings.
  • 2. Inside this chamber is a transparent glass quartz sleeve that holds a UV lamp.
  • 3. As water moves through the chamber, the UV lamp emits a germicidal wavelength of radiation through the glass and on to the water. This deactivates all living organisms.

source: excelwater.co.uk
Home Use

UV filters are compact and relatively easy to install and maintain. They can be connected to the main water supply line, and do not require any special tools or equipment. Once installed the UV systems work reliably around the clock. Water flows through the tank without the need for a holding tank or any reaction time. It is a set-it-and-forget-it type of system though you will need to replace the UV lamp once a year.

PROS
  • High-dosage systems can treat parasites that other disinfection methods cannot.
  • Every drop of water that enters the UV system is purified.
  • Requires very little energy - uses about the same energy as it would run a 60-watt light bulb.
  • Protection during natural disasters. When city water is compromised, a UV system keeps your drinking water safe.
CONS
  • High dosage UV filters can be expensive.
  • Low dosage units may not effectively inactivate some viruses, spores, and cysts. If you are going to invest in this method, be sure to get the high dosage unit.
  • UV water systems require electricity to operate so they will not work during a power outage.
  • May not be suitable for emergencies or survival needs unless the use of a generator is factored in.
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Distillation

Distillation is a process that relies on evaporation to purify water. Distillation Systems use a process of heating water to the boiling point and then collecting the water vapor as it condenses, leaving many of the contaminants behind. This process effectively kills viruses, bacteria, and all parasites.

The unit consists of three parts:

Boiling Chamber

Water enters and is heated to its boiling point; it forms steam and is vaporized. Inorganic compounds and large non-volatile organic molecules do not evaporate with the water and are left behind, separating out the contaminants.

Condensing Coils

The steam is collected and as it cools, it will then be converted back into its liquid form to form purified water.

Storage Tank

After purification the water is held here until it is used.

Distillation effectively removes:
  • Waterborne pathogens
  • Inorganic chemicals such as heavy metals and nitrates
  • Many organic chemicals
  • Soluble minerals
  • Particulates
PROS
  • It produces some of the purest potable water available.
CONS
  • Water treated with this method is stripped of important minerals which produces a flat taste.
  • The unit generates significant heat, which can be problematic in warmer conditions.
  • Low-volume units produce water slowly, while high-volume units are expensive and require substantial electricity.
  • Because it requires electricity, distillation may not be ideal for emergencies without a generator.
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Reverse Osmosis (RO)

Reverse Osmosis is a water-purifying treatment that uses pressure to filter contaminated water. As the pressurized water passes through a semi-permeable membrane, it stops almost anything larger than a water molecule from passing through. The use of sediment and carbon filters is used in this process as well.

Reverse Osmosis removes more than 90 to 99% of a wide range of contaminants, such as heavy metals, solvents, organic contaminants such as pesticides and herbicides, and pathogens including viruses, bacteria, and all parasites.

Home Application

You have two options when it comes to utilizing this water purification method at home. You can install a more robust under-counter system or a smaller countertop filter.

Under Counter System

The reverse osmosis system taps into the under-sink infrastructure you already have in place. As water passes through filters, it is sent to a holding tank that has also been placed under your sink to catch and store the newly purified water. A dedicated faucet, separate from the original, is installed on your sink and draws water from the storage tank below whenever you want access to your purified water.

Countertop System

A countertop reverse osmosis system is also available and is not any bigger than other appliances you already place on your counter. From your counter, you attach a feed line to your original faucet and the water is filtered through this countertop system. These systems are not as robust and can be quite slow in comparison, so if you are serious about using this method to purify water, an under-counter system may be the way to go.

PROS
  • Reverse Osmosis is the most effective eliminator of all disease-causing organisms and most chemical contaminants.
CONS
  • It removes sodium and healthy essential minerals. There are systems that will add them back in.
  • The process uses approximately 3 times as much water as it treats, which may be reflected on your water bill.
  • There may be some noticeable drop in water pressure.
  • This system is not a set and forget. It requires extensive care and maintenance.
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Water Purification
Water Testing Kits

Testing Your Water Supply

While stocking up on water purification tools is essential for emergency preparedness, it’s equally important to know what you’re treating. Not all water sources carry the same risks. Some may be contaminated with bacteria like E. coli or Salmonella, while others might be harboring other pathogens equally invisible to the eye. That’s where water testing kits come in. They can help you identify whether treatment is needed at all—and if so, which method is most appropriate.

DIY water test kits are widely available and easy to use, often delivering results within 24–48 hours. Many detect coliform bacteria, including E. coli, and some even test for a broader range of contaminants. You can find them online through retailers like Amazon, at home improvement stores such as The Home Depot, or through specialized suppliers like Bio-Rad for more advanced testing needs. Including a few of these kits with your water purification supplies ensures you will know what purification treatments, if any, are needed.

Check Out the Tap Water Database

This will show you what pollutants are presently found in your water supply and the source of each. It will give you advice on choosing a filter that will filter out each contaminant found. Simply enter your zip code to view a report on your local utility.

See Database