Water Purification – Methods You Should Know

Of all the things that you and I stockpile, water is our biggest problem. Putting it simply, there’s just no way of stockpiling enough water to meet our needs in a grid-down situation, no matter what we do. We use water for too many things, and in too large a quantity, to stockpile that much.

Granted, we would all have to severely curtail our water usage in a grid-down situation. But we couldn’t stop using it. Going without bathing and not keeping our homes clean really isn’t a good option, as it will promote the spread of disease. So, while we may not be using automatic dishwashers and might not be watering our lawns, we will still need water.

The average American uses 100 gallons of water per day. Of that, about half is used for gardening and watering lawns. Of the water used in the home itself, the biggest water users are the toilet (24%), showering (20%), washing clothes (17%) and various sink faucets (19%). Only about a gallon per person per day is used for drinking and cooking.

This is where the famous “gallon per person per day” that many survival instructors tout comes from. Preppers all over the place use that figure for calculating the amount of water they need. But there’s a serious problem with that. It’s not enough. That’s just enough for drinking and cooking.

In reality, we could probably get by on somewhere around five gallons per person, per day, in a survival situation. That doesn’t count gardening, but it does count washing dishes and bathing, if we are careful about how we use our water. Gardening will depend on how big a vegetable garden you have and how much rainfall you get.

But for the moment, we want to talk about that drinking water. Because of all the water we use, that’s the most critical. Drinking water, and water used in cooking, must be purified to prevent disease. Many bacteria and other microscopic organisms live in our water supply, just waiting for a chance to get into our bodies and make us sick. So, purifying that water is critical to our survival.


Filtering water is the most common means for preppers to purifying their water. But you need to have the right sort of filter. Many of the water filters on the market don’t filter fine enough to get the bacteria out; but rather, only filter out sediment. That’s not going to help.

To filter out microscopic pathogens (bacteria and their friends) you need a water filter that is rated at 0.2 microns or smaller. So a 5 micron “whole house filter” isn’t going to do you the least bit of good.

Fortunately, there are some really good water filters on the market. Two of the best are the Berkey and the Sawyer. While these are totally different systems, I would trust my life and that of my family to either of them. While a bit expensive to buy, they are actually cheaper per gallon than most other filters on the market.

Please note that you don’t need to filter water used for washing clothes, washing the floors or washing your bodies. However, you should use purified water for the dishes, so that you aren’t depositing bacteria on them in the washing process.

Reverse Osmosis

Reverse osmosis is somewhat different than typical filtration, in that it uses a semi-permeable membrane, rather than a filter element. This actually filters the water extremely well, even removing dissolved mineras. But there are two problems with reverse osmosis, from a survival point of view. The first is that it requires high pressure, which means power to operate a pump and the second is that it wastes a lot of water. So, I would not recommend a reverse osmosis system are part of your survival preparedness.


Chemical purification is used by pretty much every municipal water authority, after the water passes through filtration. That’s what the chlorine you sometimes smell in the water is. That’s actually the same kind of chlorine that’s put in pools to keep them clean, although it is a smaller dose.

You can find chlorine readily in the supermarket, sold as liquid bleach for whitening clothes. Just make sure you don’t buy the scented kind or the “colorsafe” kind. You actually want to buy the cheap stuff, as that has no additives.

To purify water with bleach, you’ll need to add eight drops per gallon and mix it. Then allow it to sit 20 minutes, for the chlorine to have a chance to kill the bacteria. For larger water containers, you might want to consider buying a graduated cylinder to measure the bleach, as there are 20 drops per milliliter. So, for example, a 55 gallon drum of water needs 22 ml of bleach to purify it.

There are other chemical purifiers on the market, such as iodine and halzone tablets; but those are both more expensive and not as effective as using liquid bleach.


Everyone knows that you can boil water to purify it, but not so many people know that you don’t have to get it hot enough to boil. Water boils at 212°F, but the bacteria die at 158°F. So, if you can heat the water to 160°F or more, you can purify it in a process known as “pasteurization.”

To make this easier, you should buy a Water Pasteurization Indicator or WAPI for short. This is a simple device, designed for use in third-world countries, but available here at home as well. It consists of a plastic capsule, with a wax bead inside it. This can either be floated in the water or hung in the water by a wire attached to the pot handle. When the wax bead melts, the water is hot enough to be pasteurized.

Solar Heat

Another way you can use heat to purify water is by using the power of the sun to pasteurize it. Simple take clean, clear soda bottles and remove the labels. Fill them with water and place them on a corrugated metal roof or a dark colored surface, in the sun. For safety, a WAPI can be added in one of the bottles. Allow the bottles to sit in the sun for a few hours and the water will be purified.

This works because the water-filled bottles act as a lens, focusing the sun’s rays and generating more heat. So it’s important to fill the bottles all the way. A bubble will reduce the amount of heat that can be generated.

The Best Purifier

The best means of water purification known is to distill the water. This means heating the water up to a temperature where it turns into water vapor (212°F) and then condensing the water vapor back to a liquid. This process causes everything else to be left behind, bacteria, chemicals and sediment, creating the purest water you can find.

Typically, stills are heated with a wood fire, but they can also be heated with solar power. This can be accomplished thorough the use of a large Fresnel Lens or by making a solar still, much like a solar oven.
The only problem with this process is that it is time consuming. You can’t distill large quantities of water quickly, unless you have a very large still. But then, you don’t need a lot of water to be purified, just what you are going to drink, cook with and use to wash the dishes.