Using Pressure Drop to Indicate When It's Time to Change Out Your Filter Cartridge

Using the “Pressure Drop” or “Pressure Differential” method to indicate when it's time to change out your Filter Cartridge is commonly used and is a simple way to monitor your filtration system. The diagram below shows a typical installation with pressure gauges installed on both the inlet and outlet sides of the filter housing.

It is crucial to maintain a 6-month filter change out schedule! Time always overrides pressure drop criteria in drinking water applications. If it has been 6 months since you last changed your filter cartridge it must be changed immediately to prevent the growth of bacteria. Regular filter replacements ensure clean, safe water for your home.

You might need to change your filter as early as 2-5 months if you notice a change in the taste, smell, or water pressure. There are many variables depending on usage, water quality, and the type of filter. If you are using an activated carbon / taste and odour cartridge a change out is required if your water tastes or smells odd.

Depending on the system pressure requirements one may choose to change the cartridge at a lower 4 to 5 PSI pressure differential to maintain desirable system pressure and efficiency. However, when pressure drops 5 to 7 PSI (Outlet pressure gauge reads between 43 PSI to 41 PSI when inlet gauge reads 50 PSI as per this example) the filter cartridge should be changed out.

Delta P (ΔP), pressure difference or differential pressure usually refers in the technical world to the drop of pressure in a piping system.

Instructions:

STEP #1 – Note the pressure readings on both the inlet and outlet pressure gauges after a clean filter cartridge has been installed, you will notice a pressure drop of 1 to 3 PSI when water is being used (this is normal) and will vary depending on the type of filter cartridge that is installed.

STEP #2 - Record the two pressures somewhere near the filter for future reference so you can see if there are any significant changes in the systems pressure.

STEP #3 – Periodically monitor the pressure drop. When the pressure drop increases typically by an additional 5 - 7 PSI, it is an indication that the filter cartridge is “loaded” (clogged with particulate) and needs to be replaced.

Additional Resources:

https://support.boshart.com/what-are-the-required-steps-to-properly-select-a-water-filter

https://support.boshart.com/how-do-i-identify-what-filter-cartridge-i-have-in-my-water-filter

https://support.boshart.com/will-your-sediment-and-or-taste-and-odor-carbon-filters-make-my-water-safe-to-drink

https://support.boshart.com/granular-activated-carbon-gac-vs.-activated-carbon-block-cb-water-filters

https://support.boshart.com/how-does-filtration-work

https://support.boshart.com/what-are-the-components-of-a-traditional-water-filter-and-spin-out-sediment-filters