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Dishwashers, particularly the newer models, are incredibly convenient. Instead of spending hours scrubbing dishes by hand, we can simply load them into the machine, hit a button, and let it work its magic. They make life so much easier—except when the dishes you pull out aren't spotless. Unfortunately, that's not always the case, and sometimes we unknowingly make small mistakes that could affect the dishwasher’s ability to do its job, leaving behind frustrating white spots or an annoying film.
To uncover the potential reasons for less-than-perfect dinnerware, we reached out to Morgan Eberhard, a senior scientist at Cascade, and Brandon Pleshek, a cleaning expert and third-generation janitor (yes, you read that correctly) who runs the viral TikTok account, CleanThatUp. Here’s how we might be making simple mistakes that are preventing our dishwasher from performing at its best.
Brebca/Getty ImagesSpotting vs. Cloudiness
- Causes of Spotting: This is typically due to calcium and magnesium left behind by hard water, explains Eberhard. If your water is hard, which means it's rich in these minerals, using a rinse aid can help reduce the effect by lowering the surface tension of the water. 'The rinse aid’s 'sheeting action' prevents water from sticking to the dishes, which stops drops from lingering and leaving behind residue,' Eberhard notes.
- Causes of Cloudiness: The cloudy residue on your glassware could also be a sign of hard water, Eberhard says. To check if this is the case, she suggests removing the film with vinegar or by washing the glass with warm water and dish soap. If the cloudiness clears up, you're likely dealing with hard water, which can often be fixed easily with a rinse aid. If it doesn’t, your glasses might be etched, meaning they have fine, tiny scratches.
A Blocked or Excessively Dirty Dishwasher Filter
This could be reducing your dishwasher’s efficiency, leading to streaky or blotchy glasses, says Pleshek. If the filter isn't cleaned regularly, at least once a month with hot, soapy water and a bottle brush, your machine might end up circulating dirt, grime, and mineral deposits right back onto your dishes. It’s also a good idea to clean the whole dishwasher every month by adding a dishwasher cleaning packet into the detergent compartment and running an empty cycle to reduce build-up. Deep cleaning should be done every few months.
Improper Positioning of Glasses
Your dishwasher loading habits may be to blame here. Eberhard suggests tilting cups and glasses on the top rack to prevent water from pooling after the wash cycle. She also advises positioning cups between the top rack’s tines, rather than placing them on top, to avoid wet spots that may form as they dry.
The Water Temperature Is Too Low
Two things can go wrong when the water temperature is too cool. First, it takes much longer for water to evaporate, making it easier for soap or mineral deposits to leave marks on your dishes. Second, if the water isn’t hot enough, it might not fully dissolve the detergents, which can result in spots or gritty residues. Aim for a water temperature of at least 120°F.
You’re Pre-Rinsing
It turns out that pre-rinsing can actually make your dishes look dirtier. 'When there’s no food on the dishes to break down or any hard water minerals because of soft water, it can remove metal ions from glassware, causing etching,' says Eberhard. It’s all about the chemistry! So instead of rinsing, try scraping off as much food as you can into the trash or compost bin, she recommends. The leftover food soils on plates will give your detergent something to work on!
The Water Temperature Is Too High
While low temperatures can cause speckling, a cloudy white residue may result from water that's too hot. If the water exceeds 140°F, etching can happen, so it’s best to avoid using the sanitize cycle too frequently, which runs at a minimum of 150°F. The optimal range is between 120°F and 140°F.
You’re Not Using the Right Amount of Detergent
Pleshek explains that using too much detergent can lead to build-up that isn't fully rinsed off, especially if you’re not running full loads. (For instance, you don’t need as much detergent for a half load as you would for a full load!) This can be resolved by hand-washing with dish soap or using vinegar to cut through the residue. However, the haziness caused by excessive detergent can be permanent—if you have soft water and habitually over-pour, permanent etching is likely.
“This milky film-like surface cannot be removed because metal ions have been removed from the surface of the glass by silica compounds,” according to GE Appliances. (In contrast, if you have hard water, you might need just a little more detergent!) Soft water users need not worry, though: A dishwasher study in 2011 found that softened water, using almost 30% less detergent, cleans just as effectively as harder water.
