We all want clean water, but we don't always take the necessary steps to get it. Most municipal water sources do an acceptable job bringing untreated water up to an established code, but there are still contaminants, which can survive the treatment center process. Homeowners who seek cleaner, purer water often install their own filters to trap those contaminants before they reach the faucet or sink. These filters range in size from large, professionally installed units located near the main water pipes, to consumer-installed filters placed directly on faucets. All home water purifiers have a filter, which must be replaced on a regular basis.

Regardless of the type of water filter, replacing it should be simple. Save the packaging from your last filter. This should contain detailed instructions on the filter’s removal and replacement. In general, a larger unit will have a special compartment, which contains a cartridge-style filter. This filter collects and removes all sorts of contaminants, from bacteria to solid particulates of metal. It must be replaced with a new filter when it has reached maximum capacity. You should prepare the new filter as you open the compartment containing the old filter. Try not to handle the old filter without protective gloves. The filtered contaminants can make you sick. Have a waterproof container (plastic bag, trashcan, bucket, etc.) ready for the old filter. Follow the specific instructions that are included with the replacement filter. Allow some water to run through the filter in order to eliminate leftover contaminants and to prime the new filter. Do not drink the water that initially comes out of the tap after replacing the filter. After a few minutes, the water should be safe to drink.

Many consumers prefer the convenience or lower installation cost of a water filter attached directly to a faucet. Installing this type of filtering system is easy. Replacement filters are sold in department stores, hardware stores, home improvement centers, or online. These filters can be switched between an active and an inactive setting. While actively filtering tap water, an indicator strip will slowly change color. When the indicator strip reaches a saturation point, the consumer should replace the filter. Most of the time, this involves purchasing a new filter and then unscrewing the housing surrounding the old one. Some systems require a short burst of water in order to force out the old cartridge, but removal and replacement instructions should be easy to follow. Once the old cartridge has been forced out, the new filter should fit snugly. The housing is then screwed back on and the entire unit is ready to begin filtering tap water again.

While it's important to know how to change a water filter, it's just as important to know when to change it. Changing a water filter too early can be costly, but waiting too long can lead to health problems and overall water quality issues. Filter manufacturers often suggest a specific timetable for changing out their products, but this schedule may be based on ideal conditions that are not present in your home. Some municipal water sources are naturally cleaner than others, so the same filtering system may perform differently depending on location and overall water quality.

Here are several methods to consider when replacing the filter in a home water filtering system:

1. The Calendar Method. Some consumers find it easiest to rely on the manufacturer's recommended replacement schedule. If a water filter is rated to last 6 months, for example, then the homeowner can mark a precise date on the calendar for replacing the newly installed cartridge. Mark the date of installation somewhere near the filter unit itself and then add the recommended date of replacement, whether it is a month or a year. Regardless of actual performance, replace the old filter promptly when that date arrives. Chances are the filter has reached its maximum effectiveness by this date and changing it regularly insures consistency.

2. The Indicator Method. Some water filters, especially those attached directly to faucets, have indicator strips, which change color when the filter has become significantly less effective. These indicators may not correspond with the number of calendar months suggested by the manufacturer, but they are usually accurate. Some water filter systems are affected by hot water flowing through the faucet; so be careful when switching from passive to active filtering mode. Once the indicator needs replacing, purchase a new filter as soon as possible.

3. The Performance Method. Some water filters perform well even months after their recommended change. Others may not last as long. Since replacement filters may be expensive, a homeowner may wait until the filter has definitely reached its maximum capacity. This is determined by informal performance tests. One test involves the time it takes to receive hot water through the tap. If all the household water runs through a professionally installed filtering system first, any significant lag time for hot water could indicate a clogged filter. When a filter becomes 50 or 60 percent clogged with contaminants, it may need immediate replacement. The water flowing through the filter becomes slower and slower, and takes longer for heated water to reach the tap.

Another performance gauge is the taste of the water. If you notice a significantly different taste in your filtered water, the water filter may have reached its limits. Municipal water treatment plants may introduce different levels of chlorine or other chemicals during different seasons, but an efficient water filter should keep the water consistent at the consumer's end. If the water becomes cloudy or has a disagreeable aftertaste, it may be time to replace your water filter regardless of the calendar month or the indicator readings.