All swimming pool filters are equipped with pressure gauges that measure the pressure within the filter in pounds per square inch. Understanding how to read a pressure gauge will tell you what is going on inside the filter.
A filter will have a low starting pressure after it has been cleaned, but a week or two later it should be normal.
When the filter varies from that normal pressure, it requires some type of service. When normal running pressure is too high, the filter is impacted with dirt and debris, requiring more pressure to push the water through the filter.
Many technicians backwash DE filters when the pressure rises by 8 to 10 pounds above normal.
When the pressure returns to normal but jumps back up in a few days, it is time to clean the filter. If the filter’s pressure is lower than normal, the hair-and-lint pot is full. This restricts water flow into the filter, causing it to run below its normal pressure.