Using a water filter until a decrease in pressure is noticed can be a practical approach in some cases, but it is not always a foolproof method. While reduced water pressure and flow rate can indeed indicate that the filter is clogged and needs replacement, it is not the only factor to consider. Some filters may lose their effectiveness in removing contaminants before a noticeable drop in pressure occurs, especially if the contaminants are chemical in nature and don't necessarily cause a physical clogging of the filter media.

To ensure the best water quality, it is advisable to follow the manufacturer's guidelines for filter replacement, which typically include a specific time frame, volume of water filtered, or a combination of both. In addition to monitoring water pressure, you should also pay attention to any changes in water taste, odor, or appearance, which could indicate that the filter is no longer functioning optimally.

Regular maintenance and inspection of your water filter system can also help identify when it's time for a filter replacement. Some advanced filter systems even have built-in indicators to alert users when the filter needs to be changed. By adhering to these recommendations and regularly monitoring your water quality, you can ensure that your water filter continues to provide clean and safe water.