Water Purification 101


One of the biggest problems in almost any survival situation is coming up with enough clean water to drink. While we should all stockpile water as part of our preps, it’s really hard to stock enough water. Mostly that’s because we use so much of it.

The average American family of four uses about 400 gallons of water per day. Granted, we would have to keep ourselves from using anywhere near that much in a survival situation; but we would still need water for a number of things. While we could forego watering our lawn and taking long, luxurious showers, we couldn’t forego many uses. About the best we could do is try to minimize them.

Most survival instructors will tell you that you need a gallon of water per day, per person to survive. But they’re only talking about drinking water and water for cooking. Even then, that gallon won’t be enough in a hot climate. You can sweat out that much in a day if it’s hot enough.

At a bare minimum, you’ll need water for drinking, cooking, washing dishes, showering, washing your clothes, cleaning your house and if you are going to raise a vegetable garden, you’ll need water for the plants as well. That comes out to somewhere between five and ten gallons of water, per person, per day, if you are being extremely miserly with your use of it.

Of that water, the only part that you need to have purified is what you drink, what you cook with and what you wash your dishes with. Everything else can be natural water, as you find it, or even gray water, which is the water you’ve already used for cleaning. I have my home plumbed in such a way so that the water from one of the bathtubs and the clothes washer are watering my garden, making use of at least some of the gray water.

Clean Water

When we talk about purified or clean water, we need to be sure that we understand what we are talking about. Napoleon is quoted as having said, “Murky water, left standing, becomes clean.” But does that mean that it’s safe to drink? No! It only means that there isn’t any sediment suspended in the water. Of all the things that can make water unclean to drink, that is actually the least of our worries.

Rather than sediment, what we need to concern ourselves with are microscopic pathogens; bacteria, viruses, and protozoa that live in the water. More than anything, it is the bacteria that can be a problem to us. While we have countless bacteria living in and on our bodies, most are beneficial to us. But these others in the water can make us severely ill or even kill us.

For this reason, it’s never a good idea to assume a water source is clean, even if it looks like it is. Bacteria are so small, that they won’t discolor the water. It can look perfectly clean and still be deadly. Even water that comes from a high mountain stream can be dangerous. You never know who might be camping upstream of you and using that stream for their personal latrine.

Always purify all water that will be consumed, used for cooking or used for washing dishes. For that matter, it’s a good idea to use purified water for washing your hands as well, especially if you are going to eat food with your hands.

Purifying Water

Purifying water means either removing or killing the microscopic pathogens in it. The city water coming from your faucet has already had this done to it. Municipal water authorities take water purification seriously, usually using a combination of methods to ensure that the water is clean.

In a survival situation, you’ll have to do that yourself. Fortunately, there are a lot of different ways in which you can purify water effectively. Let’s look at a few:

Mechanical Filtration

Filtration is probably the most common means of water purification used by preppers. The water is passed through a filter, which removes the pathogens from it. Eventually, the filter becomes clogged by these pathogens and another sediment in the water, and the filter must be replaced.

Here’s the danger though; not all water filters will provide you with pure water. A typical home water filter is rated at 5 or 10 microns. At that size, it will only remove sediment, not pathogens. You need a filter that will go down to 0.2 microns to ensure removal of 99.9% of the bacteria that is in the water. When looking at water filters for survival, ignore anything that doesn’t say that it can remove that 99.9%.

Two of the best water filters on the market are the Berkey and the Sawyer. The Berkey system is a two-canister system, with a water filter cartridge mounted in between. The larger systems use multiple cartridges to purify a larger quantity of water, but they are the same cartridges. While the cartridges for the Berkey system are rather expensive, they filter much more water than lower priced cartridges, making the overall cost per gallon much lower.

The Sawyer system uses a semi-porous fiber membrane as its filter element. This can be set up using plastic bags for the water or a five-gallon bucket. The bag systems are much more portable than the Berkey system. But the big advantage of the Sawyer system is that it is back-flushable to clean the filter. Once clean water is pushed through the filter backward, the filter is made new again. This allows the company to claim that their filters are good for one million gallons.

Chemical Purification

While mechanical filtration is the most common method used by preppers, chemical purification is the most common method used by municipal water authorities. Most of them draw water up from the deep aquifers, where they are getting water with low dissolved solids and no sediment. The chemical purification is done for safety, ensuring that the water that they deliver to your home is biologically pure.

Perhaps your tap water smells a little odd from time to time, like a swimming pool. That’s because the same chemical is used by your municipal water authority, that is used for keeping swimming pools clean; chlorine.

While there are other chemicals that can be used to purify water, chlorine is both the most common and the least costly, making it a double winner. You can easily find chlorine at any store that sells swimming pool supplies. But you can also find it in your grocery store, packaged as simple laundry bleach.

In order to use chlorine laundry bleach to purify water, you need to add eight drops of bleach to a gallon of water, mix it and allow it to sit 20 minutes. That’s it. Be sure to use basic, unscented bleach, not the color-safe kind. If you don’t like the chlorine smell in your water, allow the container to sit open overnight, someplace where it will be protected from dust blowing into it. That will allow the chlorine time to evaporate out, leaving you with purified water.

To purify larger quantities of water, such as a 55-gallon drum, you might not want to be sitting there counting out drops of bleach. It is easier to measure out the bleach in a graduated cylinder (remember high school chemistry?) and adds it to the water. Twenty drops make one cubic centimeter, so if you have a 55-gallon drum of water, you’ll need 22cc of bleach.

Heat Purification

Pretty much everyone knows that water can be purified by boiling it. But boiling water is a very inefficient way of purifying it. It takes a lot of fuel to be purifying water constantly; fuel that you need for other things. However, heat purification can still be used if you don’t have any other means available to you.

In fact, you don’t really need to get water to the boiling point in order to have it purified. The microscopic pathogens we’re talking about dying at 158°F. So if you can raise the water to above that temperature and hold it there a few minutes, you’ll have purified water.

The trick in this is knowing how hot the water is. A simple cooking thermometer will solve that problem for you. Another way to solve that problem is with a WAPI, a water pasteurization indicator. The WAPI is a simple device, developed for use in third-world countries. It consists of a plastic capsule with a wax bead inside. It is placed in the water and either held in place with a wire or a float. When the water reaches 160°F, the wax bead melts and drops to the bottom of the capsule, letting you know that the water is pasteurized.

The WAPI can also be used in conjunction with solar water purification. Clean, clear, plastic soda bottles can be turned into containers for purifying water, by the simple expedient of removing the label. Fill the bottles with water and place them on a corrugated metal roof or a dark colored surface, such as the ground. Allow it to sit in the sun and the water will heat up. With a WAPI in one of the bottles to let you know when the water is hot enough, the sun will purify your water for you.

Storing Water

As part of your stockpile, you should have as much water as you have room for. Some people store it in cleaned out, gallon-size, milk jugs. Others use 55-gallon drums. A lot will depend on the space you have available for storage.

If you are storing tap water for emergency use or any other water that you are not absolutely sure is 100% perfectly purified, it is a good idea to add bleach to the water, before sealing the container. Just like when purifying it, use 8 drops per gallon or 1 cc for every 2 ½ gallons. This is enough to ensure that nothing grows in your water, while it is in storage.