If your dishwasher is leaving food residue, streaks, or cloudy marks on your dishes, it can be frustrating—especially when you expect a spotless result after every cycle.

Poor cleaning performance is one of the most common dishwasher problems. In many cases, it’s caused by simple issues such as blocked spray arms, a dirty filter, or incorrect loading.

In this guide we explain why your dishwasher is not cleaning properly and what you can do to fix it.

1. Blocked Spray Arms

Dishwashers rely on spray arms to distribute water evenly during a wash cycle.

If the small holes in the spray arms become blocked with food debris or limescale, water cannot reach all areas of the dishwasher.

Signs this is the problem

• Dishes on one rack are still dirty
• Food residue remains after washing
• Spray arms are not spinning freely

How to fix it

• Remove the spray arms
• Rinse them under running water
• Use a small brush or toothpick to clear blocked holes

Cleaning the spray arms can quickly improve cleaning performance.

2. A Dirty or Blocked Filter

The dishwasher filter traps food particles and prevents them from recirculating.

If the filter becomes clogged, dirty water may be reused during the cycle.

Common symptoms

• Food debris left on dishes
• Unpleasant smells inside the dishwasher
• Poor overall cleaning results

What to do

Remove the filter and clean it thoroughly under warm water.

Regular cleaning helps maintain performance.

3. Incorrect Loading of Dishes

How you load your dishwasher can significantly affect cleaning results.

If dishes are stacked too closely together, water may not reach all surfaces.

Common loading mistakes

• Plates blocking spray arms
• Items overlapping
• Large items placed incorrectly

Tips for better results

• Leave space between items
• Place larger items at the sides
• Ensure spray arms can rotate freely

4. Low Water Pressure or Supply Issues

Dishwashers require adequate water pressure to clean effectively.

If the water supply is restricted, the spray arms may not operate properly.

What to check

• The water supply valve is fully open
• The inlet hose is not kinked
• There are no blockages in the inlet filter

5. Using Too Much or Too Little Detergent

Using the wrong amount of detergent can affect cleaning performance.

Too little detergent may not remove grease, while too much can leave residue.

Signs of detergent issues

• Cloudy glasses
• Sticky residue on dishes
• Excess foam inside the dishwasher

Follow the manufacturer’s guidelines for detergent use.

6. Hard Water and Limescale Build-Up

In areas with hard water, limescale can build up inside the dishwasher and reduce efficiency.

This can affect spray arms, heating elements, and internal pipes.

Symptoms

• White residue on dishes
• Reduced cleaning performance
• Build-up inside the appliance

Solution

• Use dishwasher salt if required
• Run a descaling cycle regularly

7. A Faulty Water Inlet Valve

If the dishwasher is not receiving enough water, it may not clean effectively.

The inlet valve controls the flow of water into the appliance.

Signs of a faulty valve

• Poor cleaning results
• Dishes not fully rinsed
• The machine seems to use less water than usual

Replacing the valve may be necessary if it is not working properly.

8. Worn or Damaged Spray Arms

Over time, spray arms can become worn or damaged, reducing their effectiveness.

Signs

• Cracks or visible damage
• Spray arms not spinning properly
• Uneven cleaning results

Replacing worn spray arms can restore proper water distribution.

How This Relates to Other Dishwasher Problems

Poor cleaning performance is often linked to other issues.

For example:

• If your dishwasher is also leaving water behind, see dishwasher not draining – causes and fixes
• If the appliance smells unpleasant, cleaning the filter and interior may help

When Replacement Parts May Be Needed

If cleaning and adjustments do not resolve the issue, some components may need replacing.

Common parts linked to poor cleaning include:

• spray arms
• filters
• inlet valves

Replacing worn parts can significantly improve performance.

You can find replacement dishwasher parts for many appliance brands from Yourspares.

Preventing Cleaning Problems

Regular maintenance can help keep your dishwasher working effectively.

Helpful tips

• Clean the filter regularly
• Rinse food scraps before loading
• Avoid overcrowding the dishwasher
• Use the correct detergent amount
• Run cleaning cycles periodically

Final Thoughts

If your dishwasher is not cleaning properly, the cause is often something simple such as blocked spray arms or a dirty filter. By checking these areas first, you can usually improve performance quickly.

If worn components are the cause, replacing the correct part can restore your dishwasher and ensure your dishes come out clean every time.

If your dishwasher is leaving water at the bottom as well as dirty dishes, there may be a drainage issue. See our guide on dishwasher not draining – causes and fixes.

If your dishwasher is not filling with enough water, it may struggle to clean effectively. Read our guide on dishwasher not filling with water and how to fix it.