If your dishwasher is not cleaning properly, the cause is almost always one of five things: a clogged filter, blocked spray arms, water that is not hot enough, the wrong loading or detergent, or a worn pump. The good news is that the first four you can sort out yourself in an afternoon, and only the last usually needs a technician. Before you assume the machine is dying and start shopping for a new one, work through this list. If you would rather have it professionally diagnosed, our experienced technicians can fix your dishwasher, usually the same day you call.
Here is the honest truth from the service side: most "broken" dishwashers are not broken at all. They are clogged, loaded wrong, or running on cold water. Let us go through the top five reasons in the order worth checking, easiest and most common first.
In this article
Reason 1: the filter is clogged
Please note: The tips here are for general guidance only. Home Appliance Care is not responsible for any damage, injury, or cost resulting from action taken based on this content. If an appliance is smoking, sparking, or giving off a burning smell, stop using it, unplug it at the wall, and call a qualified technician. Any repair on a gas appliance must be carried out by a licensed gas technician. When a step calls for opening up the machine or anything you are not fully comfortable with, stop and book a professional.
Start here, because this is the winner nine times out of ten. Most modern dishwashers have a removable filter sitting in the bottom of the tub, under the lower spray arm. Its job is to catch food bits so they do not get sprayed back onto your dishes. When it packs full of gunk, dirty water just recirculates, and your glasses come out gritty instead of clean.
- Find the filter. Pull out the bottom rack and look for a round, twist-lock filter in the floor of the tub(Note: If your machine has a built-in hard food disposer, you likely have a 'self-cleaning' filter and won't have a manual, removable mesh cylinder. If you can't easily find a twist-out filter, check your manual). Most twist out by hand.
- Rinse it under hot water. Use an old toothbrush and a little dish soap to clear the mesh. Do not use anything sharp that could tear it.
- Wipe out the sump. Clear any debris from the recess the filter sits in before you put it back.
- Twist it back in firmly. A filter that is not seated properly lets food bypass it, which just creates the same problem somewhere worse.
Did you know
A lot of dishwasher filters are meant to be cleaned every couple of weeks, but most people never touch them once in the life of the machine. If you have never cleaned yours and your dishes have slowly gotten worse over months or years, there is a very good chance this one step fixes everything. It costs nothing and takes five minutes.
Reason 2: the spray arms are blocked
The spray arms are the spinning paddles that fling water around the tub. Each one is dotted with little holes, and over time those holes clog with food, hard-water scale, and bits of label paper. When the holes block, the water cannot reach the top rack or the back corners, so some dishes come out spotless and others come out untouched.
- Pop off the lower and upper spray arms. Most lift or twist off without tools.
- Hold each one up to the light and check that every hole is clear.
- Poke any blocked holes clean with a toothpick, then rinse the arm under the tap.
- Spin the arms by hand once they are back on, and make sure nothing, like a tall pot handle, is stopping them from turning during a cycle.
Reason 3: the water is not hot enough
Dishwasher detergent needs genuinely hot water to dissolve and do its job, ideally around 120 degrees Fahrenheit, or roughly 49 degrees Celsius, at the dishwasher. If the incoming water is lukewarm, the detergent never fully activates and you are basically rinsing your dishes in soapy cold water. This is a common winter problem in Ottawa homes, when the water sitting in the pipes runs cold.
Save your money: the free hot-water trick
Before you call anyone, try this. Turn on the kitchen tap closest to the dishwasher and let it run until the water is hot, then start your cycle right away. This clears the cold water out of the line so the dishwasher fills with hot water from the first fill. If your dishes suddenly come out clean, the machine was fine all along, and you just saved yourself a service call. You can also check that your water heater is set to a sensible temperature.
Reason 4: loading and detergent mistakes
Sometimes the machine is perfectly healthy and the problem is how it is being used. A few small habits make a big difference in how clean things come out.
- Do not block the spray arms. Tall items, oversized pots, and cutting boards on the bottom rack can stop the arms spinning. Lay big items along the sides.
- Face dishes inward and down. Soiled surfaces should point toward the spray, not nest against each other where water cannot reach.
- Do not overcrowd. Cramming in one more bowl usually means two come out dirty. Give water room to move.
- Use fresh detergent and refill the rinse aid. Old, clumpy detergent that has absorbed moisture will not clean. Rinse aid helps water sheet off so dishes dry without spots.
- Scrape, do not pre-wash. Scrape off big scraps, but a little residue actually helps modern detergents work. Bone-dry dishes can come out worse.
People often ask: should I rinse dishes before loading?
You really do not need to, and it can even hurt. Most modern dishwasher detergents are designed to grab onto food residue, and some need a bit of soil to work against. A quick scrape to remove large chunks is plenty. Pre-rinsing every dish wastes water and can leave the detergent with "nothing to do," which sometimes leads to a chalky film. Scrape, load, and let the machine do what it was built to do.
Reason 5: a worn pump or motor
If you have cleaned the filter, cleared the spray arms, confirmed the water is hot, and fixed your loading, and dishes still come out dirty, then it is time to suspect the parts that actually move the water. The wash pump and its motor drive water up through the spray arms under pressure. As they wear, the pressure drops, and even a spotless filter and clear arms cannot make up for weak water flow.
Other internal culprits include a failing water inlet valve that lets too little water in, a worn wash-arm bearing, or a control issue that cuts cycles short. These are not afternoon do-it-yourself jobs for most people. They involve disassembly, electrical connections, and the right replacement parts for your model. This is the point to book a technician through our help page, so a pro can diagnose it correctly the first time.
Repair or replace, a quick cost reality check
If it turns out to be an internal part, the natural question is whether it is worth fixing. A rough rule many technicians use is the fifty-percent rule: if the repair costs more than half the price of a comparable new dishwasher, and the machine is past about seven or eight years old, replacement may make more sense. The figures below are general ranges to help you think it through, not firm quotes.
| Situation | Typical reality | Usual call |
|---|---|---|
| Clogged filter or spray arms | Free to fix yourself | Clean it, no service needed |
| Cold water or loading habits | Free to fix yourself | Adjust and retest |
| Worn pump, valve, or motor | A parts-and-labour repair | Get a technician quote |
| Repair near or over half a new unit | Machine likely 8+ years old | Consider replacing |
A quick diagnosis from a technician tells you which side of that line you are on, so you are not guessing with a few hundred dollars on the table.
Sources and further reading
- Home Appliance Care, in-home dishwasher service notes, Ottawa and Gatineau, 2026.
- Manufacturer guidance on dishwasher water temperature and filter maintenance (recommended wash temperature near 120 F / 49 C).
- Boulevard Home, "Dishwasher not cleaning properly, tips to try" (video, embedded above).
Frequently asked questions
Why is my dishwasher leaving food on the dishes?
The most common reason is a clogged filter recirculating dirty water back onto your dishes. Pull out the bottom rack, twist out the filter, and rinse it under hot water with an old toothbrush, then check the spray arm holes for blockages. The second most common cause is loading: dishes packed too tightly or facing away from the spray do not get clean. Clean the filter and arms, space out your load, and run a hot cycle. If food still ends up on your dishes after that, the wash pump may be losing pressure and needs a technician.
How hot does dishwasher water need to be?
Around 120 degrees Fahrenheit, or roughly 49 degrees Celsius, at the dishwasher itself. At that temperature the detergent dissolves and activates properly to break down grease and food. If the water is much cooler, especially in winter, the detergent never fully works and dishes come out filmy or gritty. An easy test is to run the nearby kitchen tap until it is hot, then start the dishwasher right away so it fills with hot water. If that fixes the cleaning, your machine was fine and the line was simply running cold.
Should I clean my dishwasher filter, and how often?
Yes, and it is one of the most valuable five minutes of appliance maintenance you can do. Many filters are designed to be rinsed every week or two, but most people never clean theirs at all. A packed filter is the leading cause of poor cleaning. Twist it out, rinse it under hot water with a soft brush and a little dish soap, wipe out the recess it sits in, and twist it firmly back. If your dishes have slowly gotten worse over time, cleaning the filter often restores the machine completely.
Is it worth repairing a dishwasher that is not cleaning?
Often, yes, because the most common causes cost nothing to fix yourself: cleaning the filter and spray arms, using hot water, and loading properly. Those should always be your first steps. If the problem turns out to be an internal part like the pump, valve, or motor, weigh the repair against the machine's age. A common guideline is that if the repair costs more than half the price of a comparable new unit and the dishwasher is eight or more years old, replacement may make more sense. A quick technician diagnosis tells you which side of that line you are on.
Quick recap
The five-minute version
- Clean the filter first. It fixes most cases on its own.
- Clear the spray arm holes so water reaches every dish.
- Run the tap hot before you start so the machine fills with hot water.
- Space out the load, face dishes toward the spray, and use fresh detergent.
- If it still will not clean, suspect the pump and book a technician.
Download the free quick guide
Keep our one-page checklist on the fridge so you can run through the five fixes before you ever call for help.