There are many factors that affect the life of your filter. First, the type of liquid filter bag you use will affect how long you have to change it. Different micron sizes will produce different results, as will every possible material. Another factor that will affect the life of the bag is the job itself. Flow rate, particle size, and countless other variables will all affect how long you will use the filter bag.
People ask this question so often because it would be convenient to have an answer. If we could tell you "change the bag every 3 weeks," you might be more likely to buy a filter. However, in an industry with so many variables, such a one-size-fits-all answer simply does not work. While determining when to change the bag is not simple, it does not have to be difficult.
While most people who are new to filtration equipment believe that they should use time to determine whether the filter needs to be changed, the indicator they should pay attention to is pressure. As liquid passes through the filter, the pressure decreases. The difference between the inlet and outlet pressures is called the "differential pressure" or "pressure drop." The higher the differential pressure, the harder it is for the liquid to pass through the filter. If the differential pressure is too high, it can affect the quality of the liquid passing through and the structural integrity of the filter.
The recommended replacement differential pressure that companies usually give is "between 20 and 25 psi." This is a good rule of thumb, but certain materials and flow rates can make this number change. Sometimes the number is even lower, so it's best to check the spec sheet and any manufacturer's instructions before you start using the filter. Many filters also have different flow and system pressure limits, so it's always a good idea to read the filter information before you buy!
