The Mechanics of Food Recirculation
Modern dishwashers do not drain and fill with fresh water between every wash phase. To meet strict Canadian energy standards, they pump the exact same 12 litres of wash water through the spray arms dozens of times. A micro-fine stainless sump mesh is supposed to trap food particles while the circulation pump runs.
When tiny coffee grounds, sesame seeds, or sandy grit settle inside the rims of upside-down glasses on the upper rack, you are looking at wash water recirculation failure. Water is picking up debris from the sump and redepositing it onto your glassware under hydraulic pressure.
1. Upper Spray Arm Nozzles Choked with Lime & Seeds
The upper spray arm spins entirely on hydraulic reaction force: water shooting out of angled nozzles pushes the arm in circles. If watermelon seeds, lemon pulp, or hard mineral scale lodge inside those tiny jet orifices, two things happen:
- The spray arm stops rotating and sprays continuously at one static angle.
- Water pressure inside the feed tube drops, allowing settled grit to fall by gravity straight into the mouths of glasses.
The Tech Fix: Unthread the center retaining nut on the upper rack, remove the spray arm, and inspect each jet hole against a light. Use needle-nose tweezers or a wooden toothpick to dislodge trapped seeds, then flush hot water backward through the center inlet.
2. Sump Fine Mesh Filter Bypassed or Torn
At the bottom of the tub sits the cylindrical filter and fine mesh plate. If this filter is seated even 2 mm crooked, or if the rubber gasket around its perimeter has dried out and flattened, wash water takes the path of least resistance. It bypasses the micro-screen completely, pulling greasy soil directly into the wash pump impeller.
3. Water Diverter Valve Motor Stuck
Modern dishwashers (including Whirlpool, KitchenAid, and Bosch) use an electronic diverter disc with a 12V stepper motor. This valve alternates water pressure between the lower spray arm and the upper spray arm. When grease coats the diverter seal or the motor's microswitch sticks, the machine starves the upper rack of pressure during the rinse phase, leaving unrinsed soapy grit baked onto glassware.
When to Call a Professional
If you have cleared the spray arm jets and cleaned the sump cylinder but glasses still emerge coated in sandy grit, the circulation pump impeller or diverter disc needs bench testing. Our technicians carry genuine OEM pumps, diverter assemblies, and delivery tubes across Greater Victoria.