Filters by the Numbers: How Many Water Filter Stages Do You Need?

Water quality is something many of us take for granted. When we turn on the faucet for a drink of water or use water in our homes for bathing, cleaning, or cooking, we often give little thought about what is in the water we use. Many homes are served by municipal water systems, which treat water with disinfectants before it is piped to residential customers. Millions of others get their water from private wells. No matter where your water comes from, it may be harboring invisible contaminants – contaminants that can damage plumbing or even make you sick. 

If you are shopping for a water filter system or a reverse osmosis filtration system, you may be stunned by the incredible array of systems available on the market. You may even ask yourself “How many water filter stages should I have?” This guide will explore water filters and what they do to protect you and your family from harmful contaminants in the water you use every day. 

Common Contaminants in Household Water Supplies

In the United States, drinking water is highly regulated for safety. Organizations like the U.S. Environmental Protection Agency (EPA) establishes standards for nuclear, biological, and chemical contaminants in drinking water supplies. Municipal water systems must adhere to these regulations, and certain states or cities may have even more stringent regulations. Despite these rigorous standards, contaminants can and do find their way into the water we use for drinking, bathing, and cooking. Common contaminants include:

• Biological – bacteria, viruses, protozoan cysts
• Heavy metals – lead, mercury, copper, arsenic, chromium
• Industrial runoff
• Agricultural runoff – pesticides and herbicides
• Petroleum residues
• Dissolved minerals
• Sediments and silt
• Disinfection byproducts – chlorine, chlorites, trihalomethanes
• Fluoride
• Radioactive elements and radionuclides

Some of these contaminants merely affect the visual or taste/odor qualities of drinking water. Others can cause severe illness or even death. To protect yourself and your family members from the harmful effects of contaminants, a reverse osmosis water system or a system with multiple filter stages is highly effective. 

One Stage. Two Stages. Three Stages and More

Shopping for a whole house water filter system can be challenging. There are dozens of models, each claiming to remove dangerous and unpleasant contaminants from water supplies. Some models have only a single filter, while others will have two, three, or even four individual filter elements to clean the water. 

To answer the question “how many water filter stages should I have?” can be even more challenging. The answer depends on the quality of the point source (municipal water service or well), the delivery method, age and condition of plumbing fixtures, and a host of other factors. In areas where water quality lags, multiple filter stages may be required to ensure water safety. In cities with good track records of water quality, fewer filter stages may be all that is needed to provide clean, freshwater for use in your home. A reverse osmosis water system is often a great choice for those concerned about water quality in the home. Even these systems may use multiple filters to deliver great-tasting, fresh, and safe water.

Different Stages, Different Filtration: Water Filters 101

In the most advanced whole house water filter systems, multiple stages tackle the tough task of removing harmful contaminants from water supplies. Filters are rated by their filter pore size and by the type of contaminants they target. Filter pore size is measured in microns; a single micron is one-thousandth of a millimeter. 

Typically, a first stage or prefilter removes large particles, such as silt, sand, and sediments. This filter, equipped with a 5-micron element, often requires the most frequent replacement in a multiple-stage system, especially in areas where water is turbid or prone to stormwater runoff contamination.

The next stages in a whole house water filter system are designed to remove specific contaminants.  Stage 2 filters may also be equipped with a 5-micron filter element, often comprised of activated carbon or a proprietary filter medium. These stages reduce or eliminate microorganisms like protozoan cysts, volatile organic compounds (VOCs), and certain chemical contaminants.

In a multi-stage reverse osmosis filtration system, the reverse osmosis filter comes next in the lineup. Reverse osmosis is a mechanical process where water is pumped under pressure through a semipermeable membrane. This membrane has a pore size of 0.0001 microns – an incredibly tiny size too small to see without powerful magnification. The membrane traps contaminants while letting water molecules pass through. A reverse osmosis filtration system stops up to 99% of contaminants from passing through; contaminants include:

• Arsenic
• Lead
• Fluoride
• Radium
• Bacteria and viruses
• Chromium

A reverse osmosis filtration system can convert seawater into safe drinking water by filtering out the salts and other contaminants in commercial applications. In the home, these same filters produce clean, fresh, and safe water for use in bathing, cooking, and drinking. 

After the water passes through the reverse osmosis chamber, it receives one final filtration process. Sometimes called a post-stage filter or polishing filter, this filter improves the taste, odor, and clarity of the water by using a carbon filter medium derived from coconut shells or similar plant materials. 

Caring for Your Multi-Stage Water Filter System

Whole house water filter systems and other water filtration methods like reverse osmosis water filtration systems do an incredible job of rendering water safe for use around the home. With up to 99% effectiveness at removing harmful or unpleasant contaminants from drinking water, these systems represent a smart investment to keep you and your family safe.

A whole house water filter system is installed between the water supply lines serving the house and the faucets or fixtures in the house. A reverse osmosis filtration system is typically installed under the sink in the kitchen. It is only used to process water for drinking and cooking. 

Maintenance of these systems is relatively easy. The multiple filter elements need only periodic replacement according to manufacturers’ recommendations. Filters may be held in screw-on enclosures or snapped into a quick-release mechanism; swapping the depleted filters out for fresh ones only takes a few minutes. 

Contaminants in the water represent a real threat to your family’s health and safety. With a reverse osmosis filtration system, you get great-tasting and safe water as well as peace of mind. Now, when someone asks the question “How many water filter stages should I have?”, you will be prepared to provide them with the answers to their questions.