Quick answer: A dishwasher not cleaning properly is nearly always a maintenance problem rather than a broken machine. Clean the filter first. It sits in the floor of the tub under the bottom rack, lifts out with a quarter turn, and a blocked one accounts for more poor-cleaning complaints than every mechanical fault combined. Then take the spray arms off and flush the jets backwards under a hot tap. After that, look at loading, because an item blocking a spray arm takes out a whole section of the wash. If dishes are still dirty and the load is cool at the end of a cycle, the water is not being heated, and that is a genuine fault.
Key Takeaways
- Filter first, monthly. It is the single highest-value thing you can do.
- Spin both spray arms by hand after loading. One tall item stops the whole pattern.
- Scrape, do not rinse. Modern detergent needs something to work against.
- Dishes cool at the end of a cycle means the water never got hot. That is a fault.
Why a dishwasher not cleaning properly is usually maintenance
Poor cleaning traces to water flow, water temperature, or how the machine is loaded. If dishes come out clean but spotty or filmy instead, that is a different problem, covered in a dishwasher leaving film and spots. For other faults, our step-by-step troubleshooting guide covers the wider checklist.
| What you notice | Cause | Fix |
|---|---|---|
| Gritty film on everything | Blocked filter | Clean it, monthly |
| Top rack dirty, bottom fine | Upper spray arm jets | Flush the jets, check it spins |
| Patches of dishes untouched | Loading blocking the spray | Reload, spin arms by hand |
| Grease not shifting, load cool | Water not hot enough | Fault. Technician |
| Chalky white haze on glasses | Hard water | Rinse aid, monthly acid clean |
| Detergent still in the dispenser | Plate blocking the flap | Keep the front row clear |
| Weak spray, everything poor | Wash pump or diverter | Fault. Technician |
The filter, and why it is first every time
Nearly every dishwasher built in the last fifteen years has a manual filter. Older machines had a hard food grinder that chopped debris and flushed it away, which was noisy. Manufacturers replaced it with a quiet filter the owner is expected to clean, and a lot of owners were never told.
Pull out the bottom rack. In the floor of the tub there is a cylindrical plastic tower, usually marked with an arrow or a padlock. Twist it anticlockwise a quarter turn and lift it out. Underneath there is normally a flat mesh screen that also lifts free.
Rinse both under a hot tap, scrub the mesh with an old toothbrush, and look into the recess underneath, which is the sump. Refit with the same quarter turn and make sure the tower locks, because a filter left loose sends debris straight into the pump.
Do it monthly. That one habit prevents most of what is on this page.
The spray arms
There are usually two, sometimes three. Each has a row of angled jets, and those jets block with seeds, grit and scale. A blocked jet takes out a whole sector of the wash pattern, which is almost always the answer to a top rack that is not getting clean while the bottom rack is fine.
Most arms unclip or unscrew by hand. Take them off, hold them under a hot tap so water runs backwards out through the jets, and clear stubborn holes with a toothpick. Do not use a needle or anything that can widen the hole, since that changes the spray pattern permanently.
Refit them, then spin each one by hand with the racks loaded. It should turn freely through a full rotation. If it catches, something in the rack is fouling it, and that item will stop the arm during the cycle.
Loading, which matters more than people expect
Water sprays upward and outward from rotating arms, so anything facing away from an arm or shielded by another item does not get washed. It is not a power problem, the water simply never arrived.
Face soiled surfaces down and toward the centre. Do not nest bowls or stack plates. Keep the front row of the bottom rack clear of large flat items, because a baking tray or cutting board there holds the detergent dispenser flap shut, so the pod never releases and the whole load runs with no detergent at all.
Angle cups and mugs so water runs off rather than pooling in the base.
Water temperature
A dishwasher needs water around 50°C to dissolve detergent and cut grease. Where hot water travels a long way to the kitchen, the first fill can be cool. Running the hot tap at the sink until it is hot before starting the cycle is a genuine improvement, and turning on a heated wash or sanitise option helps in a Winnipeg winter when incoming water is colder.
The test that separates a habit from a fault: open the door immediately at the end of a cycle. The dishes should be genuinely hot, not warm. Cool dishes mean the machine is not heating, and that affects everything at once. Detergent does not dissolve, grease is not cut and nothing dries. People often report that as three separate problems.
Hard water and scale
Winnipeg water is moderately hard. The minerals leave a chalky scale on the spray arms, the filter and the heating element over time, which narrows the jets and dulls the heat.
Run an empty hot cycle once a month with a dishwasher cleaner, a cup of white vinegar on the top rack, or a citric acid powder. Use one of those, not all three. Keep rinse aid topped up, since it handles the film on glassware that hard water leaves behind.
Detergent
Powder and tablets lose strength sitting in a damp cupboard, and under-the-sink is the dampest cupboard in most kitchens. If the problem started with a new box, or an old one, that is worth ruling out.
Scrape plates rather than rinsing them. Modern detergents contain enzymes that need soil to act on, and heavily pre-rinsed loads often come out worse. Many machines also use a turbidity sensor to judge how dirty the water is, so pre-rinsed dishes make the machine choose a shorter, gentler cycle than the load needs.
When it is a fault
Everything above is free. Past that point a few things need a technician. For a diagnosis, see dishwasher repair in Winnipeg. Technician-level faults include a wash pump that no longer generates enough pressure, a diverter valve stuck so one arm never gets flow, a heating element that has failed, or a blocked drain leaving dirty water to be recirculated.
A diverter fault has a distinctive signature. The bottom rack cleans well and the top rack never does, consistently, with clean arms and a clean filter.
When you book, leave the machine as it is. Do not unplug it and do not pull it out of the cabinet first. Diagnosis is $95 in Winnipeg and $120 outside the city, and the quote afterwards is the total rather than an addition to the call-out.
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Frequently Asked Questions
Why is my dishwasher not cleaning dishes properly?
The usual causes are a blocked filter, blocked spray arm jets, loading that shields dishes from the water, water that is not hot enough, or hard water scale. Clean the filter first, because it accounts for more of these than anything else, then clear the spray arm holes.
How often should I clean the dishwasher filter?
Monthly for most households, and fortnightly if you run it daily or scrape plates lightly. It sits in the floor of the tub under the bottom rack and lifts out with a quarter turn.
Why is only the top rack dirty?
Water reaches the upper spray arm through a longer path, so anything reducing pressure or blocking flow shows up there first. Take the upper arm off, flush the jets backwards under a hot tap, and check it spins freely by hand once the machine is loaded.
Should I rinse dishes before loading?
Scrape, do not rinse. Modern detergents contain enzymes that need soil to work against, and heavily pre-rinsed loads often come out worse. Keep bones, seeds, fruit stickers and eggshell out of the filter.
Does hard water affect cleaning in Winnipeg?
Winnipeg water is moderately hard, which leaves scale on the spray arms and the heating element over time. A monthly hot cycle with a dishwasher cleaner or a cup of white vinegar keeps it in check, and rinse aid handles the film on glassware.
When is it a fault rather than maintenance?
If the filter and spray arms are clean, the machine is loaded sensibly, and dishes still come out dirty and the load is cool at the end of a cycle, the water is not being heated. That is a heating element, thermostat or control fault and needs a technician.
