This is at a 144,000gallon church-camp pool with 2 pumps and filters that run 24/7.
Last summer we changed out the 10-year-old sand for new sand from a reputable local pool supply, and checked the laterals inside - everything looked/felt good.
But ever since then the filters seem to be working just fine except that the pressure never rises when they get dirty. They will get to the point that they stop filtering and the pool gets cloudy, but a good backwash and they'll clean the water again. After trial and error, I've been backwashing them once a week, which seems to work well.
I've verified that the gauges are working properly, I've taken the tops off the filters and looked/felt for channelling, the sand inside isn't clumpy or hard, it's easy to slosh it around inside. The free space is correct for the filters.
Any idea why the pressure doesn't rise, and/or should I be concerned about it?