This cutaway version shows how the water moves through the filter to collect in the lower bucket.
PHOTO: RUSS MICHAUD
(Editor's note: Russ Michaud owns Homespun Environmental, which sells a variety of ceramic water filters in both do-it-yourself and ready-to-use kits. For more information about his company's offerings, see the link at the bottom of this story.)
Everyone agrees that water is a must-have essential at the top of the list for survival preparations. Consequently, there are a lot of products on the market for cleaning up contaminated water to make it fit for human consumption. Here’s a quick look at the advantages of ceramic cartridges versus other filter types and discussion of a few key issues.
What is a ceramic water filter?
The ceramic filter consists of a porous ceramic shell and usually is sold as a sealed cartridge that contains some additional water purification media. A picture of a dome-shaped filter is shown here, but they can be manufactured in various shapes and sizes. The outer shell of the ceramic cartridge filters out bacteria using sub-micron sized pore openings. (A micron is a millionth of a meter). In addition, many chemicals can be filtered out using “broad spectrum” activated carbon inside the shell. Specialized filters to remove particular chemicals such as fluoride or arsenic can also be manufactured by using other media in place of the carbon.
What are the advantages of these filters?
Some popular types of filters just use small pore openings to strain out bacteria but do nothing to treat the water for pesticides, fertilizers or petroleum-based products that may be present in water from lakes or rivers. Other types of water filters will just use activated carbon for the chemicals but not have small enough filter pores to eliminate bacteria.
What are the advantages of do-it-yourself ceramic water filters?
Of the filters that treat for both bacteria and chemicals, many are sold as systems with stainless steel containers that can cost hundreds of dollars. Doing it yourself with ceramic water filters (and your own containers) is a good option as it allows for very good water quality at reasonable cost and also allows the end user to customize systems to fit their particular needs and local conditions.
Isn’t making a water filter difficult?
The basic set up of a do-it-yourself water filter is shown. This is an extremely simple system requiring two containers and a ceramic filter cartridge. The contaminated water is poured into the top container and flows through the filter. Clean water is collected in the bottom container. A key feature of this system is that it requires no electrical power to operate. It is also very easy to construct by drilling a few holes and attaching the ceramic cartridge using the supplied washers and wing nut. A spigot is used in this system to dispense the water.
“Stacked Bucket” systems like this have been used in Third World missions and disaster relief for many years, often in the place of any standing infrastructure. They can accept just about any freshwater source as the input. Flood waters, polluted streams, and rain catchments have all been used. It is an excellent low-cost alternative to using bottled water or trucking in water.
How much water and how fast?
One of the first questions most folks have is “How much water are these filters good for?” There are two answers for this question.
The filters will work for bacteria and particulates for as long as the ceramic shells are intact. The pores in the ceramic can get clogged over time, but are easy to unclog using a slight abrasive to remove the outermost (clogged) layer of ceramic. The activated carbon inside is used up after 6 to 8 months of regular use. Assuming 12 to 15 gallons per day from a natural water source, this implies the carbon will last for 3000 to 4000 gallons.
This assumes, however, that natural water sources are used. The carbon’s useful lifespan will be shortened if the water contains a lot of chemicals such as chlorinated water (i.e. tap water will use up the carbon faster and pool water a lot faster than that).
The water flow of a filter dripping out of the spout under normal atmospheric pressure depends on the water level in the container. For a standard 5-gallon bucket, it is 12 to 15 gallons per day. This is plenty of water for drinking and basic needs for a family.
One can easily increase the flow rates if needed. A very simple method to increase flow rates is to place filters in parallel. For example, if one filter is giving a flow of 1/2 gallon per hour, placing a second filter in the container will double the flow rate. (A standard 5-gallon bucket can fit up to three 4x4 filters). The downside to this method, however, is that it also costs more to implement.
Another method for increasing water flow is to increase the pressure on the filter. This can be accomplished by using upper containers that are deep to provide more water pressure or by increasing the air pressure in the container using a hand pump. The downside of air pressure is that it increases system costs and also requires manual labor.
There are several ways to provide the seal for the upper bucket; care should be taken to allow some kind of relief valve in case the system becomes over-pressurized. A good method to do this is using Gamma Seal lids. These lids can be fitted onto standard buckets and have a threaded rim and a central screw-on top. The lids will provide enough seal so that air pumps will increase the water flow when the hand pump is operated; however, they do not hold pressure for long and thus prevent system blow-outs.
A third method that is low-cost and low-labor is to add a siphon to the output of the filter. For a stacked bucket system, the siphon can double the flow of a drip system. A “separated bucket system” is shown here; this can increase the rates a lot more depending on the siphon height. Make note that if you separate the buckets, the bottom one should stay covered to prevent other contaminants from getting into the filtered water.
The dimensions of the siphon tube are critical. The inside diameter needs to be small enough that the tube can completely fill with water. The outside diameter of the tube needs to form a good seal with the filter.
There is a caveat to increasing flow rates — it decreases the “contact time” that the water has with the activated carbon and thus reduces the ability of the carbon to adsorb some chemicals. The time needed varies with the type of chemical being adsorbed so unfortunately there is no straightforward to the answer of how fast you should go. The best advice is to filter the water at the rate that is needed. The above methods can be used in combination to increase the flow rates. It becomes more of a problem keeping the buckets refilled than how much water is being filtered. At this point it is probably advisable to switch to barrels.
Ceramic carbon water filters are excellent water filter devices for individual and family sized systems. They work on both biological and chemical contaminants in water sources where many other filter types just work on one or the other. In do-it-yourself applications, they provide an outstanding value (service provided for the money spent) and allow for a wide degree of customization.
Homespun Environmental (www.homespunenvironmental.com) is a small business specializing in affordable, ceramic water filters. Emergency water kits such as the one shown here cost less than $35 (including shipping) that can be fitted into user-provided containers to create potable water in case of emergencies. At this price, it is possible for folks living in hurricane- or flood-prone areas to purchase and store them for just-in-case disaster where the local water infrastructure can be knocked out. Individual components can also be ordered that allow users to upgrade rain catchment systems, off-grid lake systems, or well water remediation.