# A dishwasher "senses" how dirty dishes are? How?
**URL:** https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109
**Category:** Factual Questions
**Created:** [October 4, 2023, 5:44pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109 "2023-10-04T17:44:34Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@CC](https://boards.straightdope.com/u/CC)
#### Post date: [October 4, 2023, 5:44pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/1 "2023-10-04T17:44:34Z")
Another article about rinsing before putting dishes in the dishwasher contains this bit: “It’s often best to use the “Auto” cycle, which senses how dirty the dishes are and adjusts accordingly.” I don’t want to debate the should you rinse question. I want to know how the machine senses how dirty the dishes are. Anybody? Buehler? Buehler?
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### Author:  [@beowulff](https://boards.straightdope.com/u/beowulff)
#### Post date: [October 4, 2023, 5:51pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/2 "2023-10-04T17:51:55Z")
Optical sensor in the waste-water circuit.
The amount of reflected light is proportional to the amount of crud on the dishes.
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### Author:  [@DCnDC](https://boards.straightdope.com/u/DCnDC)
#### Post date: [October 4, 2023, 5:52pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/3 "2023-10-04T17:52:00Z")
The machine goes through one rinse cycle. It collects the used water in a basin at the bottom of the machine, then shines a beam of light through the water. The clarity of that water then translates to a specific cycle, water usage, and time.
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### Author:  [@moes\_lotion](https://boards.straightdope.com/u/moes_lotion)
#### Post date: [October 4, 2023, 5:53pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/4 "2023-10-04T17:53:41Z")
I have a Bosch dishwasher that needed servicing last year. While the repairman was trouble shooting, he showed me where there was a turbidity sensor in the hoses that circulate the rinse cycle water. How exactly the sensor senses turbidity I don’t know but would guess some sort of optical transparency measure.
ETA - ninja’d, twice!
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### Author:  [@Munch](https://boards.straightdope.com/u/Munch)
#### Post date: [October 4, 2023, 5:56pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/5 "2023-10-04T17:56:08Z")
> [@moes\_lotion](#):
>
> ETA - ninja’d, twice!
Yeah, but you got to use the word “turbidity”, so you get awarded at least 80% credit.
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### Author:  [@solost](https://boards.straightdope.com/u/solost)
#### Post date: [October 4, 2023, 6:16pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/6 "2023-10-04T18:16:01Z")
> [@moes\_lotion](#):
>
> I have a Bosch dishwasher that needed servicing last year. While the repairman was trouble shooting, he showed me where there was a turbidity sensor in the hoses that circulate the rinse cycle water.
So a lack of ability to sense turbidity led to your dishwasher’s torpidity?
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### Author:  [@moes\_lotion](https://boards.straightdope.com/u/moes_lotion)
#### Post date: [October 4, 2023, 6:20pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/7 "2023-10-04T18:20:38Z")
> [@solost](#):
>
> So a lack of ability to sense turbidity led to your dishwasher’s torpidity?
Actually, it was the water flow sensor that was the source of the turbulence.
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### Author:  [@Yllaria](https://boards.straightdope.com/u/Yllaria)
#### Post date: [October 4, 2023, 6:35pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/8 "2023-10-04T18:35:53Z")
> [@Munch](#):
>
> Yeah, but you got to use the word “turbidity”, so you get awarded at least 80% credit.
FYI - When you’re doing turbidity testing, your ability to keep the equipment properly washed is critical.
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### Author:  [@moes\_lotion](https://boards.straightdope.com/u/moes_lotion)
#### Post date: [October 4, 2023, 6:41pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/9 "2023-10-04T18:41:29Z")
> [@Yllaria](#):
>
> FYI - When you’re doing turbidity testing, your ability to keep the equipment properly washed is critical.
Even though the OP said that the question of “should you rinse” wasn’t to be debated, the turbidity sensor topic came up because my wife likes to rinse everything first, and the repairman told her that it made the process less energy efficient. I didn’t press him for more details, and my wife is still rinsing.
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### Author:  [@Yllaria](https://boards.straightdope.com/u/Yllaria)
#### Post date: [October 4, 2023, 6:44pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/10 "2023-10-04T18:44:18Z")
I wonder if using too much detergent gives a false ‘still dirty’ signal.
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### Author:  [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)
#### Post date: [October 4, 2023, 7:56pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/11 "2023-10-04T19:56:11Z")
> [@moes\_lotion](#):
>
> my wife is still rinsing
My wife pretty much washes the dishes by hand before putting them in the dishwasher, which is how they are sanitized. It’s just easier not to argue.
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [October 4, 2023, 8:03pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/12 "2023-10-04T20:03:18Z")
I fear men like us with wives like that are legion. Preach it Bro!
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### Author:  [@gnarator](https://boards.straightdope.com/u/gnarator)
#### Post date: [October 4, 2023, 8:30pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/13 "2023-10-04T20:30:12Z")
> [@Omar\_Little](#):
>
> My wife pretty much washes the dishes by hand before putting them in the dishwasher, which is how they are sanitized. It’s just easier not to argue
> [@LSLGuy](#):
>
> I fear men like us with wives like that are legion. Preach it Bro!
I wish. I can’t get my wife and daughter to rinse anything, or even throw trash (paper, plastic, eggshells, bones) away. They also won’t listen to my advice on loading, then blame the machine for not getting dishes clean. I had to spend a Saturday afternoon a few weeks ago cleaning out the chopper, sump, and spray arms.
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### Author:  [@bob\_2](https://boards.straightdope.com/u/bob_2)
#### Post date: [October 4, 2023, 10:09pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/14 "2023-10-04T22:09:16Z")
Only I am allowed to load the dishwasher. No one else loads it correctly. I scrape debris off plates before putting them in and rinse the filter every couple of weeks
We have a Miele machine and when I start it, it immediately shows how long the cycle will take. The variation is not great ± 15 minutes, but it does not wait for an initial prewash. I have often wondered what it is actually doing.
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### Author:  [@kanicbird](https://boards.straightdope.com/u/kanicbird)
#### Post date: [October 4, 2023, 10:22pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/15 "2023-10-04T22:22:06Z")
> [@moes\_lotion](#):
>
> wife likes to rinse everything first, and the repairman told her that it made the process less energy efficient. I didn’t press him for more details, and my wife is still rinsing.
Dishwashers are actually designed to use food particles in the water to help dislodge food from the plates/pots etc. The commercial one we have at our firehouse uses nothing but very hot water (no detergent) and must have such food particles in the wash cycle or less it is just hot water and it’s not getting clean.
In home ones the detergent can do this, however it is less efficient and effective, that first prewash is before detergent is discharged and having particles in the water stream can make a difference. We also have a diswasher with a grinder that helps this process even more. We can and do put un-rinced dishes in and they come out very clean, it also keeps the sink cleaner and available as dishes go direct to dishwasher, not the sink.
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### Author:  [@kayaker](https://boards.straightdope.com/u/kayaker)
#### Post date: [October 5, 2023, 12:24pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/16 "2023-10-05T12:24:08Z")
> [@Omar\_Little](#):
>
> My wife pretty much washes the dishes by hand before putting them in the dishwasher, which is how they are sanitized
That’s what I do, but I’m a man. I prefer to hand wash the dishes. My gf insists the dishwasher needs to be used occasionally, so when we use it I lightly wash the dishes and then put them in the dishwasher.
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### Author:  [@InternetLegend](https://boards.straightdope.com/u/InternetLegend)
#### Post date: [October 6, 2023, 5:25am UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/17 "2023-10-06T05:25:50Z")
What is it about handwashing dishes that you prefer? If you just enjoy the process, are you close enough to Albuquerque to come visit me, say, twice a week?
Our old dishwasher was mediocre, and we had to really be sure there was nothing too difficult for it on the dishes. Then we got a fancy-pants Bosch that works wonders on almost all dirt (dried oatmeal is the one consistent exception). I’ve even gotten so confident in its abilities, if I’m feeling lazy after making something that uses a lot of pans, I’ll stick them in there, too! (I know it’s not best practice, but at this point I’m pretty sure the pans will outlast me no matter how I wash them.)
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### Author:  [@kayaker](https://boards.straightdope.com/u/kayaker)
#### Post date: [October 6, 2023, 11:54am UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/18 "2023-10-06T11:54:19Z")
> [@InternetLegend](#):
>
> What is it about handwashing dishes that you prefer?
I’m able to quickly wash, dry, and put away everything, getting the kitchen back in order.
The alternative is to rinse everything and put it in the dishwasher, where it will sit for a few days until the dishwasher is full and ready to run. Then I have to put everything away the next morning.
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### Author:  [@pulykamell](https://boards.straightdope.com/u/pulykamell)
#### Post date: [October 6, 2023, 11:57am UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/19 "2023-10-06T11:57:19Z")
Huh. I do most of the dishwashing and just throw in the dishes pretty much willy nilly in there (I have no system for loading other than not doing something obviously stupid like overlapping plates) and they come out clean as a whistle every time. I absolutely do not rinse but will scrape off big food particles. Dishwashers are magic to me.
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### Author:  [@kayaker](https://boards.straightdope.com/u/kayaker)
#### Post date: [October 6, 2023, 12:43pm UTC](https://boards.straightdope.com/t/a-dishwasher-senses-how-dirty-dishes-are-how/991109/20 "2023-10-06T12:43:57Z")
I guess it’s just me. I wash as I go while I’m cooking, the 5 minutes afterwards I wash the dishes and utensils that remain and the kitchen is back in order.
When we use the dishwasher, I find myself looking inside it for my microplane I used the previous day.
If not for my gf, I’d take out the dishwasher and replacer it with….anything. Maybe a kegarator? Additional cabinet?
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