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Common Dishwasher Problems

last updated 27 Jan 2016:

Busy lives now mean the dishwasher is no longer a luxury appliance, it’s a necessity.  Any problems or faults with your dishwasher are normally unexpected and extremely inconvenient.  Before you go booking an engineer let’s see if we can help you fix the fault yourself.

 

How A Dishwasher Works

First of all it's always helpful when diagnosing faults on dishwashers if you have an understanding of how they work:


My Dishwasher Won't Start

If your dishwasher won't start at all check the following possible faults and problems:

Power

It's easy to take it for granted that a dishwasher will remain plugged and powered. It's also very easy to forget that dishwashers need power before they'll work. Sounds ridiculously simple, but it's always worth it to check!

Make sure the dishwasher is switched on to start with, then check that it's plugged in and that the circuit breaker hasn't been tripped.

If you know what you're looking for, it might be worth checking the plug (after switching off the dishwasher and removing it from the socket!) for signs that it's broken or faulty.

If the circuit breaker has been tripped, you should try to find out what tripped it and get any shorts fixed by a professional engineer. Sometimes the dishwasher itself can cause shorts if the heating element has burned out.

Flow

Some dishwashers, occasionally marketed as being eco-friendly, need water to start flowing through them before they are able to start.

These dishwashers might require you to turn on the taps in the sink above the dishwasher, or they might require you to pour a large amount of water on the inside bottom of your dishwasher before they will start.

Dishwasher Thermal Fuse

The problem may be with the thermal fuse. It's usually in the control panel, and can be checked for circuit continuity. If it's blown, you'll need to buy a new thermal fuse.

Dishwasher Door

Sometimes, the door switch might be defective. This stops the dishwasher from working, as it's impossible to detect when the door is safely closed. As with the thermal fuse, test the door switch for continuity and replace if defective.

The door latch assembly might be physically broken. These cannot be repaired, and will almost certainly need replacing.

Dishwasher Electronics

The control panel may be defective. If this is the case, a new control panel can be obtained fairly easily, but you should be certain that the control panel is at fault first. The control panel doesn't usually start to fail until a dishwasher is very old, so check other options first.

The timer may be malfunctioning. Bear in mind that the timer is frequently misdiagnosed as the cause of a non-starting dishwasher. Check all other possible causes thoroughly before checking the timer.

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Why is My Dishwasher Not Cleaning Properly

Below are the most common causes for your dishwasher not to be cleaning properly:

Poor Loading

Without doubt, the most common cause of a dishwasher not cleaning plates and crockery properly is because it's been badly loaded into the machine. Good advice when loading the dishwasher is to make sure you leave a space between dishes, so the water can reach and clean all the surfaces.  Also, before closing the door spin both of the spray arms by hand to make sure that they can spin freely without catching on anything.

Too Much/Too Little Detergent

Detergent and wash action are designed to break down food particles that are on the cutlery and crockery during the dishwasher cycle. So if you use too little detergent, your load won't be cleaned properly. But on the other hand, if you use too much then it can fail to dissolve and leave your dishes with a white residue on them.

Empty Rinse Aid Reservoir

The rinse aid compartment of your dishwasher needs to be topped up regularly to eliminate the risk of getting water marks on your cutlery and glasses.

It Needs Salt

Dishwashers need salt to activate the water softener in the machine. Soft water works more effectively and means there won't be as much streaking on the dishes. A basic rule of thumb is to replenish the dishwasher granular salt, roughly once a month.

Spray Arm Blocked

The spray arms below each basket are designed to turn as water is forced through them.  Often small foreign objects enter the spray arm and end up blocking the small holes where the water is supposed to sprayed out.  Any blocked holes will also prevent the spray arm from turning.  Carefully inspect each spray arm and remove anything that shouldn't be in there! 

Dishwasher Is Not Draining Properly

If your dishwasher is failing to drain the water fully then some dirty water is going to remain in the machine during the cycle of washing and rinsing.  There are a number of reason why your dishwasher isn’t draining see below for more information

Rinsing Before You Load

Some people do and some people don't, and it's a bone of contention for a lot of dishwasher users – but the truth is that it's best if you don't rinse dishes and glasses before you load it up. By not rinsing them, you allow the detergent to cling to the dirt particles rather than letting the suds foam up and leave your glassware looking cloudy.

Water Isn’t Hot Enough

If you suspect the water isn't heating properly then it could be the heater element or thermostat that has developed a fault.

Wrong Program

Setting your washing machine to the wrong program can start a cycle that isn't sufficient for the load you've got in it. Change the setting and see if it makes a difference.

Dishwasher Needs Cleaning

It makes sense to clean your dishwasher thoroughly every now and then. The best way to do this is to run the hottest cycle empty with a professional dishwasher and washing machine detergent and limescale remover.

Clogged Drain Pool or Filter

If the dishwasher has a clogged filter or drain pool, a quick and simple clean will usually sort it out. If you do this, but the dishes still come out flecked with food, it might be worthwhile to check and see if your filter is blocked.

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My Dishwasher is Leaking from bottom of door

A dishwasher leaking from the bottom of the door means that there is a gap between the rubber door seal which is normally fixed to the lower part of the dishwasher, and the dishwasher door.  Fixing the problem is usually straightforward and inexpensive and can be repaired by even the beginner DIY'er!

Food deposits breaking the seal

You’ll be forgiven to think that because your dishwasher is used to clean your crockery every day that the inside of the dishwasher will be squeaky clean. This in actual fact is far from the truth. Unless you make it a weekly job to clean the inside of your dishwasher food deposits, grease, and other foreign objects will build up and ultimately affect the performance of your dishwasher. The most common reason for a leak at the bottom of the door on a dishwasher is food and grease deposits getting underneath the seal.

The image below is of a comparatively clean dishwasher lower door area and seal. Notice the greasy deposits running underneath where the door seal will close to create a water tight seal. This area needs to be kept clean and should be part of your routine when you empty and clean your dishwasher filters.

Dishwasher not level

The door may close in an 'out of line' position if your dishwasher is not level.   This will create the smallest of gaps for water to leak out.  Whilst this is not so common it is a possibility and should be checked, particularly if your dishwasher has been recently moved or your floor recently altered.

Dishwasher Door Seals

Having ensured that the door area of your dishwasher is clean and free from any foreign objects, and that your dishwasher is on a level surface then it is time to check your door seals for wear and tear.  If there is any sign of perishing or damage then you'll need to replace them.

For further more detailed advice see our 'dishwasher door seal' article.

How to replace the lower door seal on a dishwasher:

How to replace the upper door seal on a dishwasher:

Dishwasher Valves

Older dishwashers might start to accumulate broken valves. If your water inlet valve gets stuck, you will see flooding start to occur. This normally means that you have to replace the valve.

Hoses

Over time, kinks in a hose can develop into breaks and leaks. Again, this is a problem you'd expect to see on an older dishwasher.   If you're experiencing problems with leaks around the back or sides of a dishwasher, it's more likely to be due to a break in a hose. Locating the hose to be replaced should be pretty simple – just locate the puddle of water, and check the hoses nearby for breaks.

Feet

If your dishwasher is not level on the floor, it will often leak water. Other than moving the dishwasher to more level ground, the only way to fix this problem is to adjust the feet if your dishwasher has adjustable feet, or use makeshift feet to alter the level on the fly.

Draining

If your dishwasher has a serious problem with draining, it can lead to leaks. If the leaking is a secondary problem, stemming from your dishwasher draining incorrectly, check out our guide below if your dishwasher won't drain.

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Why is My Dishwasher Making a Noise

Dishwashers are quickly becoming an essential convenience for the modern home. And while they may make our everyday lives a little bit easier, they soon become much less of a godsend if they start making an annoyingly loud noise whilst washing the dishes.

Whatever the cause for your loud dishwasher, it's often easy to fix. Here are four of the most common causes.

Bumping/Banging

This kind of noise could be the result of not loading the dishwasher correctly. Bumping and banging can also be caused by loose or worn spray arm mounts. This would result in the spray arm wobbling excessively and catching on the load baskets.  Before closing the dishwasher door give the spray arms a spin by hand and make sure they aren't catching on any crockery or cutlery.

High-Pitched Squealing

A faulty wash pump or drain pump could be the cause a high-pitched squeal. This is possibly due to water penetration, as a result of worn shaft seals. Worn spray arm bearings can also create a similar noise.

Whistling Noise

This could be the result of an unusual problem with the water inlet, at either the valve or air brake system.

Grinding Noise

There are several reasons which could explain why your dishwasher is making a grinding noise. First, check the drain, as bits of plastic and glass can gather in the drain pump and make a grinding noise as water flows through the system.

A grinding noise could also indicate that the pump is wearing out which is definitely worth checking out. If your pump or water inlet valve doesn't work properly, it could lead to water overflowing.

Dishwashers are generally robust and reliable appliances, but if yours has a fault it's always better and cheaper to replace the faulty part rather than buying a brand new appliance. Check out our range of top-brand dishwasher spares and parts.

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My Dishwasher Won't Drain

A dishwasher failing to drain is very frustrating problem to have. Failure to drain properly is also one of the most common reasons that a dishwasher will give your dishes a lacklustre clean. It is usually due to a blockage or clog, whether a single object or an accumulation of organic matter.

Preventing Blockages

If you wash for too short a period of time, or at too low a temperature, you will eventually end up with a build-up of food waste, resulting in a blockage that is very difficult to remove. You can avoid having to remove blockages so frequently by simply using the hot wash setting and longer wash programs more often. Dishwasher salt is important to help prevent build-up of limescale, which can cause damage to filters and contribute to clogs over time.

Check Your Dishwasher Filters

If you find a blockage or clog, you might also find that your dishwasher's filters have been damaged. Filters are especially susceptible to damage from sharp, small, solid items that find their way into the dishwasher, but may also simply accumulate damage. If a filter has been damaged, it will need to be replaced.  Check out our video on cleaning and replacing filters.

Check Your Drain Hose Isn't Blocked or Kinked

A drain hose can become blocked very easily if kinks and sharp bends develop in the hose. This will definitely cause a drainage problem, and over time could develop into a leak. Kinky drain hoses are a fairly frequent cause of dishwasher drainage problems, but luckily they're quite easy to replace..

Check Your Drain Pump

A less frequent cause of a dishwasher failing to drain is a broken drain pump. You can test a drain pump with a multimeter for electrical continuity, or check it visually for blockages. If your drain pump's significantly worn, it may require replacement.

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My Dishwasher Leaves A White Residue

If your dishwasher leaves a white residue behind on your dishes, it is usually down to only a handful of potential causes.

We'll address potential problems here, hopefully allowing you to identify the problem source.

Dishwasher Detergent

Too Little

Detergent and wash action are designed to break down food particles that are on the cutlery and crockery during the dishwasher cycle.  With the presence of salts that are naturally in our water a soluble compound is formed and suspended in the water ready to be pumped out at the end of the wash cycle.  If there is not enough detergent, for the length of cycle, then these compounds will not be held in suspension and will leave a white residue coating on the contents of the dishwasher.

Too Much

Although less likely, it is possible that using too much dishwasher detergent could lead to some of it failing to dissolve, clogging your dishwasher with white residue. If you find that you have been using too much detergent, you should check your dishwasher for blockages caused by too much detergent residue.

Too Cold

If your dishwasher isn't heating properly, your detergent might not be dissolving properly.

This could be due to a problem with the dishwasher's water heater, a problem with the connection between the control panel and water heater circuit, or a problem with the control panel itself.

Too Short

Using your dishwasher for a short wash cycle may cause the detergent to fail to properly dissolve.

In all these cases, you may want to check for blockages and run the dishwasher while empty to attempt to dissolve any remaining detergent residue.

Hard Water

Mineral deposits might be left in your dishwasher if you live in a hard water area. This can be fixed with dishwasher cleaning products in the short term, but you might want to take a longer-term solution.

If your dishwasher has an internal water softener, it may have broken down. Consider replacing the offending part.

Dishwasher Salt

If the white deposit has a salty taste then it could be a poorly fitting salt cap or perished seal.  Check that it is fitted correctly and that the seal is in good shape.

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My Dishwasher Smells

A smelly dishwasher is one of those irritating problems that can hang around for ages, getting worse and worse, unless you fix it sharpish. It can be easily dismissed as a minor annoyance – unless, of course, you take a minute to consider where the smelly water is actually coming from.

It's unlikely that waste water is entering your dishwasher from a really nasty source unless multiple parts have failed at the same time, however water staying in your dishwasher or entering through the sink can be just as bad.

Dishwasher Air Gap

The air gap is designed to stop backflow, and as such if your dishwasher starts to smell you should check to see if the air gap is blocked.

It might also be the case that the pipe between the dishwasher and air gap is blocked.

In case the blockage cannot be removed or flushed out, it will be necessary to replace either the pipe or the air gap.

Waste Pipe

Incorrectly-fitted plumbing could cause dirty water to hang around in your system.

Check your dishwasher's waste pipe, and make sure that it's secured in as high a position as it can be. If your waste pipe isn't secured high up underneath the sink, waste from your dishwasher or directly from your sink can sometimes be pushed back up the pipe and into the dishwasher.

You can secure your waste pipe in the correct position using a hose clamp.

Dirt And Waste

To remove dirty water from your dishwasher, flush out the pipes with soda crystals and water. Clean the filter out, and make sure there are no blockages in the system causing difficulty in draining. If your dishwasher is having difficulty draining, it may cause bad smells.

Finally, wipe all parts of the dishwasher clean, as it may be a temporary problem. If a particular part still smells after you've cleaned it – for example, the door gasket – you should replace it.

By Lee Gilbert

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