Dishwasher detergents

Dishwasher detergents

Tablet or powder? See which type tops our test.

Don't waste your money on a dud detergent. We put them to the test on 6 stains, including egg yolk and baked-on cheese.

From our test

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About our test

Plates are treated with egg yolk, starch, baked-on cheese, red wine, coffee and minced meat.

We measure the amount of light reflected using a spectrophotometer. We then wash them using the manufacturer’s recommended dosage, putting each detergent through 4 test loads. We then measure the reflectance again to assess how much food residue/stains remains and compare it to the initial readings. We average the results for each type of stain across the 4 loads.

Claims

Some products claim to contain rinse-aid or to be septic tank-safe. We’ve included these claims but haven’t tested them.

Almost all tablets claim to contain rinse-aid. Powders don’t have rinse-aid as it needs to be released at a certain point of the wash, which is impossible with powders. If you’re using powder and your dishwasher has a rinse aid compartment, we suggest using rinse aid to avoid water spots on your dishes.

You should always consult your septic tank manual or manufacturer before using a new dishwasher detergent.

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Tablet or powder?

While tablets perform better than powders, this superior cleaning comes at a cost. The powders in our test cost between 15 and 42¢ a wash, while the cheapest tablet was 32¢ a load. When you’re standing in the supermarket aisle make sure to check how many tablets a pack contains to make sure you’re getting the best value for money.

Ingredients

Water alone doesn’t clean dishes well, so what’s commonly in dishwasher detergents that makes them work?

In 2007, a law change prohibited the sale of dishwasher detergents with a pH higher than 12.5. Before this change, dishwasher detergents might have done better job at cleaning, but they could also contain caustic ingredients, resulting in a high pH reading. None of the dishwasher detergents in our test has a pH above 11.1.

These are popular “builders” used in dishwasher detergents. Builders increase the cleaning effect and help soften water, making it easier for surfactants to break down food particles. The Environmental Protection Authority (EPA) classes sodium carbonate as toxic if ingested or inhaled and an irritant to skin and eyes, while sodium silicate is toxic if ingested and corrosive to the skin and eyes.

This is a common bleaching agent. It removes the colour of stains left by food and helps break down food particles. The EPA advises it is irritating to the eyes.

These are surfactants, which lower the surface tension of the water helping lift food particles, such as grease, away from the dishes. They also help dry dishes and prevent water stains. Most AEs are toxic if swallowed and can irritate the skin and eyes. Some can also damage your eyes.

These are common enzymes used to break down and remove starch and proteins in food. While some enzymes in dishwasher detergents aren’t dangerous if ingested, they can irritate the skin and eyes and affect the respiratory system if inhaled.

This is often used to make the dissolvable wrapper on many tablets, so you don’t need to unwrap the tablet before putting it in the dishwasher.

Safety advice

It’s important to take care when using and storing household cleaners, especially around children.

To limit the chances of a child accessing dishwasher detergent, don’t add detergent to your dishwasher until just before you turn it on. Make sure any un-dissolved detergent is cleaned off dishes and out of the machine once the wash is complete. And always store detergents in a locked or high cupboard.

If dishwasher detergent is ingested, immediately call the National Poisons Centre (0800 POISON or 0800 764 766) for treatment advice. If the person has difficulty breathing or is unconscious, call an ambulance immediately.

Too many bubbles?

If your dishwasher is producing too many bubbles or the tablet isn’t dissolving completely by the end of the wash, then you may have a water issue.

Often this is because there isn’t enough water in the wash or the water isn’t hot enough. If you are using an “eco” or water-saving mode, then try using the detergent on a normal cycle. If you are using a powder, you can also try reducing the dosage amount. In some cases it may also be due to the hardness of the water, in which case check with the detergent manufacturer as to what to do.

Not all dish drawers are recommended for use with tablets. A dish drawer is smaller than a standard dishwasher and they use less water, so there may be too much detergent in a tablet. Check your manual or with your dishwasher manufacturer to see if you can use tablets in your dish drawer.

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