Pentair Quad D.E. Filter: Diatomaceous Earth Entering the Pool
Diatomaceous earth returning to the pool through the return jets — visible as a milky white cloud in the water or a white powdery deposit on the pool floor — means DE is bypassing the filter cartridges entirely. On a properly functioning Quad D.E. filter, all water passes through the DE-coated cartridge fabric before returning to the pool, so the DE stays inside the filter. When it doesn't, the Quad D.E. manual points to two causes: physical damage to a cartridge, the air bleed cap screen, or the manifold; or cartridges that were not correctly installed after the last cleaning.
When DE Appears in the Pool
DE return typically appears in one of three situations:
- Immediately after startup or after adding DE: A small puff of DE at startup that clears within a few minutes can be normal as the DE coat settles. A continuous milky return that does not clear indicates a problem.
- After a backwash: The cartridges are bare after backwash — DE must be re-applied. If DE continues to appear after re-coating, the problem is structural (damage or installation).
- Mid-cycle with no recent maintenance: A cartridge has developed a tear or crack during operation.
Cause 1: Torn or Damaged Cartridge, Air Bleed Cap Screen, or Manifold
The manual's first cause is physical damage to any component the water passes through. Any tear, hole, or crack creates a bypass path where DE-laden water flows through without filtration. Follow this inspection procedure:
- Shut off the pump at the circuit breaker.
- Open the Manual Air Relief Valve on top of the filter. Wait until all pressure is fully relieved and the gauge reads zero.
- Remove the clamp nut (P/N 198098z) and lift the lid to disassemble the filter per the manual's "Disassembling the Filter" instructions.
- Remove all four cartridges and lay them on a flat surface for inspection.
- Inspect each cartridge carefully for tears, pinholes, cuts, or cracks in the pleat fabric. Pay particular attention to the top and bottom end caps where fabric meets plastic.
- Inspect the air bleed cap screen at the top of the internal assembly. This small screen can develop tears that allow DE to pass directly into the return flow.
- Inspect the top manifold and bottom manifolds for cracks or fractures — a cracked manifold creates a bypass gap that bypasses the cartridge fabric entirely.
- Replace any damaged component. Replacement cartridge P/Ns by model:
| Model | Replacement Cartridge P/N |
|---|---|
| QUAD 60 | 178654z |
| QUAD 80 | 178655z |
| QUAD 100 | 178656z |
Cause 2: Improperly Installed Cartridges
The manual's second cause is cartridges that are not correctly seated. The Quad D.E. uses four cartridges that must be positioned vertically and properly secured between the top manifold and bottom manifolds. If a cartridge is tilted, shifted, or not fully locked into its seat, a gap opens between the cartridge end cap and the manifold. DE-laden water flows through that gap instead of through the cartridge fabric, and passes directly to the return side.
This cause is most likely after any recent disassembly — cleaning, inspection, or cartridge replacement. Disassemble the filter and reinstall all four cartridges:
- Shut off the pump, open the air relief valve, and wait for gauge to read zero.
- Disassemble the filter per the "Disassembling the Filter" instructions.
- Remove all four cartridges.
- Reinstall each cartridge one at a time, ensuring it sits perfectly vertical and is fully seated at both the top manifold and bottom manifold connections.
- Confirm there are no visible gaps between any cartridge end cap and its manifold seat.
- Reassemble the filter per the "Reassembling the Filter" instructions.
After Repair: Re-coat and Monitor
After replacing or reinstalling cartridges, always re-coat all four cartridges with the full recommended amount of diatomaceous earth per the manual's "Coating Cartridges with Diatomaceous Earth" section before restarting. Run the filter and observe the return jets for several minutes. A brief initial cloudiness that clears quickly is normal; continuous DE return after a few minutes indicates the problem has not been fully resolved and inspection should be repeated.