Why do domestic dishwasher cycles take hours instead of being extremely fast like commercial dishwashers?
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Commercial dish machines are essentially just Sanitizing the dishes. They will do some rinsing of the bits that are left on the dishes when you send them in, but the essential function is sanitizing, as high temp machines reach a minimum of 180F in rinse, which kills any bacteria, or low temp machines use harsh chemicals like chlorine to kill any bacteria. I work in kitchens and train my staff that dishes should go in mostly clean or they’ll still have debris on them. Those that don’t listen end up running them through again. There is a setting on most machines to lengthen the cycle, which keeps it in wash mode a bit longer for more debris filled dishes, we use it for glassware and flatware. The regular setting runs for 1 minute for high temp machines, so super quick and efficient. It also recycles the water from the rinse cycle for the next wash cycle and has a booster heater that ensures you are starting hot to reach those high temps. On top of that you have the use of extremely harsh and corrosive chemicals that are frankly dangerous in their concentrations. Household machines will essentially scrub your dishes, using different sprayers, water pressure, angles etc. to wash the debris away, running through several cycles to ensure this. They almost certainly don’t maintain the high temps needed so are reheating the water through each cycle. They also use much less corrosive chemicals. I always hit the sanitize button at home to reach higher temp and kill bacteria, it’s not using harsh chemicals to do so like a low temp commercial machine. My dream is a commercial dish pit at home, I wouldn’t mind doing the dishes at all…at work the dish pit is my zen area and would rather wash dishes when behind than do just about anything else. Zone out and run racks.
First off, commercial dishwashers are frequently actually sterilizers. You need to wash the dishes before they go in. Strong chemicals and extremely hot water are also involved.
Home dishwashers have no real need for speed. Do you really care how many hours it takes to finish when you’re sleeping anyway? If you really need that one thing, you’re just going to hand wash it anyway. Much more relevant performance metrics are things like energy efficiency and noise.
Contrast this with a restaurant which has to get another sitting going immediately after you leave. They need those dishes back immediately and they have the health inspector breathing down their neck at the same time…
I used to be a dishwasher at a nursing home. I blasted all the food and gunk off the dishes with a sprayer right after meals before it had time to dry on them. They went straight into the dishwasher which uses extremely hot water and industrial chemicals to sterilize everything. It gets hotter than your dishwasher at home, and it’s not so much working to get food off as it is to sterilize and degrease everything with steam. It’s expensive, huge, and hot, and it’s not working to get grandma’s mashed potatoes from last night off the plate it dried onto overnight because the person washing already did that.
It’s about energy efficiency and priorities. Consumer dishwashers in the 1970s were very fast but used a lot of energy and a lot of water. Looking up the cycle times for the popular 1970s Westinghouse SFK series consumer dishwasher a normal wash dry cycle was under an hour. It’s unintuitive but todays consumer dishwashers use a lot less energy and a lot less water but comes at the cost of taking 2-3 hours for a normal cycle. This trade off is generally acceptable since most consumer households do not use the dishwasher more than once a day. Fill the dishwasher throughout the day, run it after dinner and empty it in the morning.
The priorities of a commercial restaurant are different. Fast cycles are important since the flatware and utensils will be used multiple times a night thus you want to run multiple cycles as quick as practical. The speed is accomplished by higher temperature and higher water pressure. This means more energy and more water. You can further speed up the turn around by requiring a quick manual prewash in a sink. So commercial dishwashers are deigned for quick cycles.
You must (or are supposed to) wash dishes before they go into the commercial ones. Those are more about sanitizing and food safety while being quick. They take lots of very hot water as well as lots of chemicals that usually come in giant containers.
At home, you aren’t in a hurry to get dishes back out and the whole point is to make it less tedious. You can store a reasonable amount of the chemicals you need that will last a long time.
Commercial dishwashers don’t do the whole job. A domestic dishwasher is designed to take a plate just after someone’s eaten off it and then clean it completely. If you did that with a commercial dishwasher you’d end up with grainy food and sauces everywhere, and probably break the dishwasher because they’re designed to finish off the washing process to a perfect commercial standard, rather than wash the entire dish.
Commercial dishwashers use a fair amount of more chemicals then house ones, and so much more water. And also require you to pre-rinse the dishes quite well.
You will be looking at 2 types or a conveyor system. One type is a high heat system that uses a booster to heat the water up to a scalding temp on the rinse cycle to sterilize the plates, and it usually runs for 60 seconds. The second uses a sanitizing agent, and runs a little longer, at 90 seconds. A conveyer system can have either, and usually takes longer per tray but since the trays are moving in the grand scheme of things is quicker.
If you are using a dishwasher – you have to pre-scrape and pre-rinse your plates. Right before the plates go in there is a spot with a hand held hose sprayer that you would spray both the fronts and backs of plates to remove food waste. For irregular items like pots, inserts, etc would require a quick scrub ideally.
Dishwashers of this type also use loads of water. We are talking at least 8 liters for a single tray unit. It uses the rinse water from the last load to clean with and then will rinse with fresh water and add in sanitizer or have the water boosted.
They also take a lot of maintenance to be fully functioning. Tearing down at night to make sure the sprayer arms are free from debris and that all the traps to catch waste are clear as well.
Also – there are variations as well.
Most people at home don’t want to deal with that amount of effort.
Commercial dishwashers.. “time is money, space for flatware is money, getting an extra set of covers in is money”… domestic dishwasher is “it goes on after dinner, as long as it’s done by breakfast it’s fine, energy and water efficiency is money”….
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