Landed Home Drain Tray Filled with Dust: Grille Unlatched
A unit fouls again quickly after a wash, so a deeper clean is proposed. Whether the filter is clean because it worked.
By Team Snowflake | Updated 24 Aug 2026
How this presents
Dust and deposit inside a unit only weeks after a wash, where the system normally stays clean far longer than that. The filter itself is barely dirty. No other change has been made to the installation.
- Setup
- Toshiba Ducted7-9 yearsLandedTanglin
- Misread as
- A wash that did not work, given how quickly the unit has fouled again.
- Check first
- Whether the filter is loading up normally between services
What else produces this
A clean unit refouling within weeks while its filter stays clean is a contradiction worth stopping on, because a working filter gets dirty. A filter that stays clean is being bypassed, and the commonest reason after a wash is that the grille holding it was not latched shut. Air takes the gap in preference to the filter, and everything it carries goes straight into the unit behind it.
Refouling within weeks, on a system that normally stays clean for far longer, places the change at the wash.
A filter that is barely dirty while the unit behind it is not shows air is bypassing it entirely.
A return grille left unlatched leaves a gap that unfiltered air takes in preference to the filter.
No change anywhere else on the installation confirms nothing else is contributing.
Why it happens
A latched grille forces every cubic metre through the filter, because there is nowhere else for it to go. An unlatched one hangs a few millimetres proud and leaves a continuous gap along its edge. Air follows the easier route, so the filter catches almost nothing and the coil, the wheel and the tray collect everything instead. It takes weeks to become visible, by which time the wash is a memory.
What resolution involves
The grille is latched properly and the unit cleaned again, which is a second visit nobody wanted. The check belongs at the very end: close the grille and confirm every latch has engaged. A filter that stays suspiciously clean between services is the same signal arriving later, and it deserves attention rather than satisfaction.
How to tell it worked
How dirty the filter has become by the following inspection, and not how clean the unit looks today. A filter loading normally proves the air is going through it, which is the only thing that was ever wrong.
Before you approve a quote
A filter that stays clean is being bypassed
- A latched grille leaves air nowhere to go but through the filter. Unlatched, there is a gap.
- A filter still spotless while the unit behind it fouls is a warning, not a good result.
- Close and confirm every latch before leaving. It is the final step and the easiest one to skip.
Questions this case answers
Can dust collecting in the drain tray mean the tray is damaged?
How can the filter be clean and dust still get in?
What happens if a return-air grille is not relatched after a wash?
Can I check this myself before agreeing to tray work?
Ready to get started?
Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.