Few things are more frustrating than to see the very stuff that is supposed to be filtering your pool water leaking into the pool. The common culprit involved in DE powder going back into your pool is torn grids but there are a number of other causes as well. Here are a few things to check to help you troubleshoot this annoying problem.
As mentioned above, this is probably the most common issue. Over time, small tears can develop in the grid fabric and provide a gateway for DE to sneak into your pool. Carefully inspect all grids ; the good news is you can replace individual grids so if you find only one or two with tears, you do not need to replace the entire assembly.
When you check the grids, also take a glance at the plastic collars where they attach to the manifold. Even though the grid fabric might be intact, a crack in this small part would mean the entire grid needs to be replaced – sorry!
Some DE filters, like the Hayward Perflex, have “fingers” instead of grids. These tube-like tentacles can also crack and require replacement. Other parts to look at while you check the tubes are the bump shaft o-rings, diaphragm gasket, the top and bottom tube sheets, or possibly loose tube sheet bolts.
Over time, the pipe assembly inside the filter tank can crack and leak DE. Assess this part for any damage and while you’re there, check the associated o-ring. If the o-ring shows signs of wear, it might not be sealing properly and should be replaced.
The manifold is the cross-shaped top piece that holds the grid assembly together. There could be two issues here, either cracks in the manifold itself or a worn manifold o-ring. Try your luck to see if you can get away with replacing just a small o-ring or have to spend a bit more to buy a new manifold.
If all of the filter tank internals are in tiptop shape, the valve on the top or side of the tank could be your DE-leaking villain. More specifically, the gasket inside the valve which can be cracked or worn through. A common cause of damage to this part is the pool owner changing the valve handle position while the pump is running (you know who you are).
Pump Suction Leak
Surprise! Your DE filter could be entirely blameless while its sidekick, the pool pump, causes all the trouble. A suction leak in the pump can push some DE into the pool via the skimmer or main drain when the pump is turned off. If you’ve already exonerated your filter and valve from any blame, inspect the pump for a suction leak. Some common parts to check are the lid o-ring, drain plug o-ring, and pump union o-rings.
If you still have an issue with DE in your pool after checking all of the above, you might need to have a pool professional come take a look. For those fortunate enough to have found just a torn grid or two, please be sure to check out our guide How to Replace DE Filter Grids.