You either have holes in the fabric of the grids, or a crack in the manifold that the grids attach to. It can also mean a broken air bleeder tube or assembly. Finally, DE in the pool can mean that the multiport or push-pull valve is allowing powder to bypass the filter. You will notice this most when adding new DE powder after backwashing, but you can test this at any time. The best method to determine the cause is to remove the grids and clean/ inspect thoroughly.
Filter Grid Replacement
Grids and manifolds vary by manufacturer and by size. DE grids are usually $15-25 per grid; and you may expect to pay $75-100 for a manifold. Labor is usually less than one hour. You can buy the entire set of 8 grids for a lower price usually, and most of the time, it is best to replace all grids at one time. When replacing all the grids, do it upside down, with the manifold on the ground, and then work the bottom spreader plate on the top, spacing all grids correctly. If handy with an awl, torn grids can be sewn instead of replaced.
Poor Water Quality
It could be a problem with your multiport or push-pull valve. The valve could be allowing water to bypass the filter and return to the pool unfiltered. Perhaps you are not running the filter long enough. Perhaps there is not enough DE powder in the filter or too much DE powder. You may also need to backwash the filter or remove the grids and clean them manually. Poor sanitation, poor water balance, and pool circulation could be another cause, and it could have nothing to do with the filtering at all.
How Long Should I Run My DE Pool Filter Each Day?
You can run your filter just as much as you need. Careful experimentation will show you when the water quality begins to suffer. Many people with smaller, older equipment (filter/ pump) run their systems 24 hours per day. The average (I would guess) would be about 16 hours. But it depends on your system. Size, age, degree of usage, debris load, and sunlight are a few factors that call for extra filtering. If you’re too frugal with the electricity, you may have to pay more in chemical costs.
Leaking DE Filter
Most DE filters have a belly band clamp with a large O-ring between tank halves. The O-ring can become distended or flattened and may need to be replaced if water is dripping from the center clamp.
Caution: DO NOT remove the center clamp while the pump is running and without first releasing pressure inside the tank. You may notice your multiport valve leaking in one or more areas. If your push-pull valve is leaking out of the backwash port (where the hose attaches), the plunger needs either replacement or a new set of O-rings.
If your DE filter tank is leaking, and not from the belly band, bulkhead fittings, or air bleed assembly, but in the tank itself, through a pinhole or crack, replace the tank half or entire filter immediately. There is no safe and effective way to repair tank damage.