The right way to do the dishes (according to science)

There are few household jobs more ordinary than doing the dishes.

Except, from a hygiene point of view, some of the habits we’ve inherited around washing dishes aren't particularly good ones.

Research into domestic kitchens has found potentially harmful bacteria in sinks, sponges and dishwashing water.

Some people soak dishes before washing. Others turn on the faucet and get straight to work with a sponge. Some rinse carefully. Others leave the suds to drip dry.

So, what is actually the right way to do the dishes?

[ Don't want to read the science? Skip to the bottom for the conclusions and sources ]

Rule #1: Don't leave dirty dishes soaking in a communal bath

We know, this one is controversial. Some households SWEAR by soaking dishes in a tub. But here's what science actually says:

A lasagna dish with something welded to the bottom may benefit from a little water and detergent sitting inside the dish for a while. Filling the sink with dirty dishes and leaving the whole lot sitting together is another matter.

The problem isn't simply that the water looks disgusting. Food residue provides organic material for microorganisms, and dishes contaminated with raw foods can introduce potentially pathogenic bacteria into the dishwashing water.

Researchers studying domestic dishwashing have specifically examined Salmonella, Campylobacter and E. coli O157. Their experiments showed that during washing, bacteria can be transferred, through splashing and such, from contaminated dishes into the dishwashing water and from there onto other dishes and sponges. Those sponges can subsequently transfer contamination onto kitchen surfaces.

In other words, that bowl of gray water isn't necessarily containing the mess. It can help move it around.

Temperature matters, too. Research examining bacteria in dishwater found that at around 113°F (45°C) — already uncomfortable for prolonged bare-hand washing — Staphylococcus aureus experienced only a slight reduction. Much more effective bacterial reduction occurred at temperatures above 131°F (55°C).

That's one of the fundamental limitations of hand-washing: the temperatures your hands can comfortably tolerate aren't necessarily the temperatures that are most effective against microorganisms.

The better way

Scrape food into the trash or food-waste container first.

If something genuinely needs soaking, put a small amount of warm water and detergent inside that particular pan or dish, rather than turning your whole sink into a bath for everything you've eaten from that day.

Don't leave dishes that have contacted raw meat, poultry, seafood or eggs sitting around with everything else. Wash them promptly and clean the sink afterward.

The USDA specifically recommends cleaning sinks with hot, soapy water after contamination and notes that foodborne pathogens can persist surprisingly well in kitchens: Campylobacter can survive for up to four hours and Salmonella for up to 32 hours on surfaces.

Rule #2: If you're washing by hand, rinse

There's a reason professional food-safety procedures distinguish between washing, rinsing and sanitizing.

Washing and rinsing are not the same job.

Detergent helps loosen fats, proteins and food residues so they can be removed from a surface. Rinsing then physically carries away the loosened material, dirty wash water and cleaning chemicals.

The FDA's warewashing guidance explicitly calls for washed utensils to be rinsed so that abrasives and cleaning chemicals are removed or diluted before sanitizing.

So if you're hand-washing, don't scrub a plate in increasingly dirty dishwater and put it straight onto the drying rack covered in that same water.

Wash it. Rinse it with clean water. Then allow it to dry.

And, where food safety genuinely matters, for example after utensils have contacted raw meat, cleaning and sanitizing are separate steps.

USDA guidance similarly instructs people to wash utensils with soap and water, rinse them and then sanitize when enhanced food-safety precautions are required.

One important caveat: this doesn't mean you should rinse dishes before putting them in the dishwasher.

Scrape large pieces of food off, certainly. But modern dishwashers are designed to perform their own wash and rinse stages. Pre-rinsing everything under a running faucet can simply add unnecessary water to the process.

Rule #3: Don't assume hand-washing saves water

People are often skeptical about this one, but hear us out.

A dishwasher is an appliance spraying water around for anything from 15 minutes to a few hours. Surely standing at the sink and washing everything yourself must use less?

Usually, no.

In 2026, consumer organization Which? compared hand-washing with 33 recently tested dishwashers. It estimated that washing by hand used around 1.2 gallons (4.5 liters) of water per place setting.

A dishwasher on its normal program averaged just 0.24 gallons (926 ml) per place setting. On eco mode, that fell to 0.18 gallons (696 ml).

For 14 place settings, that's roughly:

• Hand-washing: 16.6 gallons (63 liters)
• Dishwasher, normal program: 3.4 gallons (13 liters)
• Dishwasher, eco program: 2.6 gallons (9.7 liters)

That made the dishwasher around 80% more water-efficient than hand-washing in Which?'s comparison, rising to around 84% on eco mode.

And compact dishwashers can use even less water per cycle.

Loch's Capsule Solo uses just 0.69 gallons (2.6 liters) of water on its 15-minute Quick Wash, and 0.90 gallons (3.4 liters) on its Eco cycle.

That 15-minute program is designed as a "meal wash": load the dishes you've just used, run the cycle, and have them ready again rather than letting them accumulate in the sink. Loch's own comparison data estimates that manual washing can use around 10 times more water for the same amount of washing over time.

Older independent research has reached the same general conclusion. A University of Bonn study cited by Australian consumer organization CHOICE found that washing a comparable full load by hand used about 26.4 gallons (100 liters) on average, although people's habits varied enormously — from 8.7 gallons (33 liters) to an extraordinary 116.2 gallons (440 liters). A dishwasher doing the same load used about 3.4 gallons (13 liters).

How can a dishwasher possibly use so little?

Because it doesn't behave like a running faucet.

A dishwasher takes in a controlled amount of water and recirculates it under pressure, repeatedly directing that same water at the dishes before draining it and moving on to the next stage.

So instead of fresh water continually disappearing down the drain, a relatively small quantity of water does a lot of work.

That's the efficiency advantage of machine dishwashing: lots of mechanical cleaning action without lots of fresh water.

And with a compact dishwasher like Capsule, you don't need to wait until you've accumulated a full-size dishwasher's worth of plates to take advantage of it.

Rule #4: Remember that your sink isn't necessarily clean

A kitchen sink looks like a cleaning place.

Microbiologically, that's a dangerous assumption.

One study followed ten ordinary US household kitchens over two years and sampled eight locations for microorganisms. The sink and sponge were among the most heavily contaminated areas.

Fecal coliforms were detected in 63% of sink samples and 67% of sponge samples. E. coli was found on 16.7% of sampled sink surfaces and 33.3% of sponges. The researchers also detected Salmonella and Campylobacter.

That doesn't mean every kitchen sink is going to make you sick. But it does demolish the idea that "it went in the sink" is synonymous with "it became hygienic."

The sink is where we wash food, rinse utensils, empty dirty dishes, handle food packaging and sometimes deal with juices from raw meat. It is therefore an obvious crossroads for cross-contamination.

That's why the USDA recommends cleaning sinks with warm, soapy water and, when appropriate, sanitizing or disinfecting them after contamination.

Rule #5: Your sponge deserves even more suspicion

If the sink is questionable, the sponge may be worse.

A 2026 study from researchers at Germany's Federal Institute for Risk Assessment investigated what happened when kitchen sponges were exposed to Salmonella Enteritidis, E. coli and Staphylococcus aureus.

All three pathogens persisted in the sponge for at least two weeks. E. coli and Salmonella established particularly large populations, and the researchers demonstrated that organisms could transfer from sponges onto kitchen surfaces through ordinary contact. Even three days of drying did not eliminate the pathogen populations.

Perhaps the most unsettling finding was that appearance and smell weren't reliable ways of telling whether a sponge was microbiologically contaminated.

A sponge can, and does, effectively become a reusable transport system for whatever it encountered previously.

Rule #6: Clean-looking isn't necessarily hygienically clean

This is where dishwashers have another advantage.

Dishwasher cleaning combines several things at once: detergent chemistry, mechanical spray action, controlled temperatures, repeated rinsing and drying.

Research comparing hand and machine dishwashing found bacterial reduction was dramatically faster in the machine. Counts of Enterococcus faecium in dishwasher wash water fell by more than three log units within five minutes, whereas hand dishwashing produced only a 0.7-log reduction after 43 minutes.

More importantly, the supposedly clean dishes told the same story.

Researchers found that dishes washed by hand retained, on average, 13 to 26 times more E. faecium than those washed by machine. They concluded that, from a hygienic standpoint, machine dishwashing was superior.

More recent research into domestic dishwashers confirms that temperature, cycle duration, final-rinse conditions and detergent all contribute to reducing microorganisms. Higher temperatures and longer cycles generally produce greater microbial reductions.

That doesn't mean every dishwasher cycle sterilizes everything — it doesn't. "Clean", "sanitized" and "sterile" have different meanings.

But it does mean a dishwasher can create cleaning conditions that are difficult to reproduce consistently at the kitchen sink.

So, what is the right way to do the dishes?

If you have a dishwasher, the answer is pleasingly simple:

Scrape. Load. Wash.

Don't waste gallons of drinking water meticulously pre-rinsing dishes that your dishwasher is about to wash anyway. Remove large scraps, load it properly and let the machine do the washing and rinsing.

If you're washing by hand:

1. Scrape first. Get food scraps off the dishes before they enter the sink.
2. Avoid the soak. For stubborn food, soak the individual pan or dish rather than submerging everything together in dirty water.
3. Wash with detergent. Use clean, appropriately warm water rather than allowing heavily contaminated dishwater to become progressively dirtier.
4. Rinse with clean water. Don't leave dishes coated in detergent and used washing water.
5. Air-dry where practical. Avoid transferring contamination back onto clean dishes with a dirty dish towel.
6. Treat your sink and sponge as things that need cleaning too. Particularly after handling raw foods.

And if you have the choice between washing by hand and putting it through a modern dishwasher, the evidence increasingly points in one direction.

The dishwasher isn't the lazy way to do the dishes.

In many circumstances, it's the cleaner, more hygienic and dramatically more water-efficient way to do them.

A note for small kitchens

Not having room for a conventional dishwasher doesn't change the science. Compact and countertop machines use the same basic advantage: a controlled quantity of water can be recirculated under pressure rather than disappearing continuously down the drain.

For example, Loch's Capsule Solo uses 0.69 gallons (2.6 liters) on its 15-minute cycle and 0.90 gallons (3.4 liters) on Eco, according to its technical specifications. Its 15-minute program runs at 158°F (70°C) — conditions that would obviously be impractical for bare-handed washing.

The point of a small dishwasher, then, isn't simply saving yourself a chore. It's bringing the water efficiency, controlled temperature and repeatability of machine dishwashing into homes where a conventional dishwasher doesn't fit.

And that may be a much better way to think about doing the dishes: not how much effort you put into scrubbing them, but how efficiently you can get them genuinely clean.

Sources

• Food Protection Trends — “A Comparison of Hand- and Machine Dishwashing from a Hygienic Standpoint”
  Compared bacterial reduction in hand washing versus machine dishwashing and found substantially better hygienic performance from machine washing.
  Read the study
• Journal of Applied Microbiology — Domestic dishwasher hygiene study
  Examined how dishwasher temperature, detergent, rinse conditions and cycle duration affect microbial reduction.
  Read the study
• International Journal of Food Microbiology — Cross-contamination during domestic dishwashing
  Investigated the transfer of organisms including Salmonella, Campylobacter and E. coli during hand dishwashing and via sponges and washing-up water.
  Read the study
• Journal of Foodservice — Effect of dishwashing temperature on bacteria
  Studied the effect of water temperature on bacterial survival during hand dishwashing, including Staphylococcus aureus.
  Read the study
• USDA Food Safety and Inspection Service — Kitchen food-safety guidance
  Guidance on cleaning sinks, utensils and kitchen surfaces after contamination, including survival times for foodborne pathogens such as Salmonella and Campylobacter.
  Read the guidance
• U.S. Food and Drug Administration — Food Code
  Sets out the distinction between washing, rinsing and sanitizing, including the need to rinse away loosened debris and cleaning chemicals.
  Read the Food Code
• Which? — Dishwasher vs hand-washing water use
  Compared recent dishwasher test data with estimated hand-washing water use and found dishwashers to be substantially more water efficient per place setting.
  Read the Which? analysis
• CHOICE — Dishwasher vs washing by hand
  Summarizes research, including University of Bonn findings, showing that manual washing can use far more water than machine dishwashing.
  Read the CHOICE analysis
• Journal of Environmental Health — Household kitchen contamination study
  Surveyed domestic kitchens and found high levels of contamination in sinks and sponges, including fecal coliforms and E. coli.
  View the PubMed record
• Journal of Food Protection — Pathogen survival in kitchen sponges
  Studied survival and transfer of Salmonella, E. coli and Staphylococcus aureus in household kitchen sponges.
  View the PubMed record