Apparently pre-rinsing confuses the dishwasher or something. Not doing it leaves me with residue all over the other dishes though 🤷

Do you run the water in your sink until it’s hot before turning on the dishwasher? Most kitchens are set up so they use the same water line, and starting with cold water if you don’t do it will make it clean worse.

It can depend on your dishwasher.

Fancier ones have heating elements to control the temperature.

Obligatory obstinance: if that was important to the process why does the machine not handle it?

That said, I do run the water until it is hot. Typically to wash the dishes that require hand washing like my nonstick pans.

Interestingly, where I live I have never, ever seen a dishwasher installed with a hot water line. Even the cheapest dishwashers heat their own water, and around here we apparently always plumb them to the cold water for some reason, even though I'm sure plumbing to hot water would at least save time if not get better results.

Looks like there's something wrong with your dishwasher. I've had this effect once on one that couldn't heat up the water any more.

It depends a bit on what exactly the residue is you're talking about, but usually it's grease that wasn't properly picked up by the water, just redistributed among your dishes. That is usually because the dishwasher detergent did not properly activate, which in turn is usually because the water does not get hot enough. (Never mind some fats also just stay solid at room temperature.)

A properly working dishwasher does not leave any residue on your dishes.

That's a thing with diswashers in North America, but not in Europe. In Europe, dishwasher are almost always connected to the cold water line only. OP seems to be posting from New Zealand, I don't know how they handle it.

It's handled like that in North America, because their mains electricity doesn't output enough juice to operate a water boiler at a reasonable speed:

https://en.wikipedia.org/wiki/Mains_electricity_by_country

So I imagine, in pretty much the rest of the world, it works like you described for Europe...

Are you adding detergent to the pre rinse, or are you just throwing in one of those crappy packets?

Melted cheese and dried egg yolks are two things that even commercial dishwashers have trouble with.

Watch this if you think your dishwasher sucks.

Indeed! They got it right with powdered dishwasher soap in the first place.

Ah, hello fellow Technology Connections viewer!

I'm the opposite. All I've known is direct connection to the household hot water tank. The dishwashers all have a "Heat Boost" option which activates an element inside to add more heat if you want, but generally hot water tanks are kept about 57°C, I've never in my life used the heat boost setting. That's for sterilization.

It can, but the water heater in your building/house is a better heater than the dinky one built in to the machine

Use prewash detergent

Powder detergent only for both washes

Stack the dishwasher according to the manual

Don't leave your dishes for a week before putting them in the dishwasher

I was ready to riot if I didn't see TC in the comments.

Whelp, time to break out the industrial dishwasher.

Whats the difference?

This just feeds the dishes to a woodchipper for easy disposal so you can buy new dishes.

Magnificent, what will they think of next?

I was shocked that I had the opportunity to post it, to be honest.

Confirming, connected to cold water here in NZ.

You can only choose one of the four

I just watched through the video someone else posted, and connecting to the hot water line seems to be a North America thing. Presumably due to the 110v power supply taking a really long time to heat.

It’s funny cause i was just talking about this video the other day with someone who didn’t know you have to run the tap hot before starting the machine. It’s just such a good video.

Just watched the video someone else posted. My machine doesn't have a pre-wash section as far as I can tell, but I'll throw some extra powder into the bottom for the pre-wash cycle and see how it goes.

I usually just wash it twice and it works.

But back when I washed dishes at Cracker Barrel I remember having to scrape that crap off “clean” dishes.

When I was living in a trailer I used an organic pre wash solution that used no water and was 100% eco friendly to save water. Highly reccomend the heeler pre wash

That was fantastic, thanks!

Some of the key things were to put separate powder in for the pre-wash (mine doesn't have a separate pre-wash section as far as I can tell), and to not put so much detergent in. We have soft water, and apparently that means if you fill the thing up (or use a tablet/pod) then you might be using too much detergent which means it might not all come off in the final rinsing stage.

Yp, started doing that and it worked in mine. You'll need to do some trial and error to get the right amount, but TC is right.

I swapped $40 pods that gave me 80 loads for $8 powder that lasts hundreds

I hate these commercials and I find it funny that they pay money to run them in my country where we have so much water we're practically drowning. We drink tap water and we leave the tap running for a quite some time just to get nice cold drinking water.

I could not give a damn about saving tap water. The dishes are rinsed before they go in the dishwasher.

This is a classic example of an American company assuming everyone else in the world think exactly like them, and subsequently completely fail with their marketing, at least in my part of the world.

One of the greatest USian scams to date. Still wastes water btw.

That depends on how far from your machine your hot water heater is, and if your machine compensates for water temp with a heating element or discharging cold water until the temp increases but as a general rule: yeeuh

I think they're asking why does the machine not purge the line to make sure there's hot water. Why do I have to run the hot water faucet until it's hot when the machine could just do that and then drain the cold water?

As others have pointed out, it can be done albeit with more attention to detail than commercials imply. I wanted to mention the game changer for me was very reluctantly splurging for the expensive high-end tripple soap pods. These really made a big difference in my washer. I look for deals and buy them in bulk.

Tips I've learned that helped:

• use detergent powder instead of pods. It let's you experiment with different amounts and dial in the right amount for a run. Generic is fine, they all do about the same amount of work.
• Run your faucet till hot water comes out, it makes it so the pre-rinse has more ability to soften crud on the surface of the dishes.
• pre-rinsing the dishes isn't necessary for cleanliness, but scraping food bits off will mean your debris filter fills up slower so you don't have to do the gross task of emptying it as often.
• add detergent in the dip on the door. This gives the pre-wash yet again more ability to attack food bits on the first cycle.
• USE RINSE AID. I helps the dishes dry at the end of the wash.

I mean, that's a thing in areas of the US too. I'm in the US and where I live it isn't unusual for people to have safe drinkable freshwater springs just spontaneously pop up in the middle of their yard. You can drive a sandpoint basically anywhere around here and get practically drinkable water. I say practically just because, legally speaking, potable water wells still need to be drilled far deeper than a sandpoint. But if you actually test the water coming out of most sandpoint wells in the area, odds are it would test perfectly safe provided there's no farm runoff there or something. So in my area the water conservation marketing falls just as flat.

Different electrics, so their in-built heaters can (and are built to) operate from the cold water line.

NA dishwashers do have a heating coil, but most are only hooked to the hot water line, so that the wimpy heater doesn't have to do quite as much work or at least doesn't have to work as quickly.

This was on QI.

The enzymes in the dishwasher tablets need some dirt to glom onto, to be able to work. So pre-rinsing can make them less effective.

Even if yours has a heating element it’s a good idea to preheat the water. This is covered in the TC video

That would significantly increase the amount of water the machine utilizes, which would push it out of alignment with efficiency regulations. There are a ton of people who don't care about this and who wouldn't want to use the extra water

I've had the heating element stop working before. Dishes came out warmish and often dirty.

Replaced it and found an added bonus of the troubleshooting paperwork attached to the front kick-plate. This allowed me to reset the system and verify all pieces were operating correctly.

If that were true, dishwashers wouldn't start with a pre-rinse before the detergent goes in?

It wouldn't waste more water, just more would go through the machine. If the pre-heating is necessary for it to work properly, the regulations need to take that into account, since that water is being wasted whether the operator runs it from the tap or the machine does it automatically.

I wonder if this could be done by the dishwasher with a temp sensor and program at the start of each load (run until hot, drain, start wash). i assume it would hurt their water efficiency claims to dump a bunch of water down the drain at the start of the wash though

We don't need high voltage actually. By pumping cold water through the block of an honest American diesel V8, it can be heated quickly. Every house includes one for this purpose. I love the sound of it starting in the morning to heat water for my shower.

Pre rinse recycles the water. So the fats and such the enzymes work on are still there to help the process.

Nah, someone else posted a video that goes through it in detail. The pre-rinse is 10 mins (depending on dishwasher) of splashing plain water around and around to get the grubbiest bits off, then it dumps the prerinse water and gets clean water for the main cycle where the detergent goes in.

One of the key tips in the video was to add detergent in the prerinse detergent section (some open section that lets it go in straight away), or if your dishwasher doesn't have one then just straight on the door or in the bottom. Just a small amount so the pre-rinse cycle has detergent in it so can get more off before the main cycle.

The only thing I've found about putting dishes in dirty is that some fancy dishwashers on the "auto" setting will sense how dirty the pre-rinse water is and set an appropriate wash cycle. If you've pre-rinsed, then it won't find much and will put it on a light cycle. This can lead to dishes not being clean if they are actually really dirty but you rinsed off the loose stuff already. But it can be worked around by just setting the cycle instead of leaving it on auto.

The QI monkeys are just buzzing around on the net finding factoids for the show, you can often find untrue or misrepresented ones.

Most people don't run their hot tap prior to running their dishwasher. It's really only if you notice an issue with your dishes being fully cleaned that you would even need to do it

I mean you could get a 240V line to your dishwasher in North America since a split phase 240V is what comes into the house. I'd rather the 240V water heater just do it instead.

Are you saying that dish washers are a scam and that they waste water?

Obligatory Technology Connections video insert

would make things more complicated - you now have to add an extra pathway from the waterline directly to the drain with an extra thermal sensor, or else you flush the pre-wash detergent down the drain.