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Comment by amiga386 | Hacker News Reader

> > Run your kitchen sink hot water a little before starting to get warmer water into the dishwasher

> Note: this only makes sense in the US (or wherever else it's common for your dishwasher not to heat its own water).

I don't think this is a US-vs-world issue. Other countries' dishwashers are also connected to the hot water supply.

Rather, Technology Connections is suggesting a hack.

Your dishwasher, wherever in the world you may be, will start up by using whatever water it can get for an initial rinse of the dishes, and it will measure how dirty the water is after this initial rinse.

Normally this water will be tepid. But if you make it hot by running your hot tap first, the hot water will rinse more dirt off the dishes than tepid water, the dishwasher will detect more dirt, and so it will assume the dishes need more aggressive cleaning, and adjust its program accordingly.

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> Your dishwasher, wherever in the world you may be, will start up by using whatever water it can get for an initial rinse of the dishes, and it will measure how dirty the water is after this initial rinse.

> Normally this water will be tepid. But if you make it hot by running your hot tap first, the hot water will rinse more dirt off the dishes than tepid water ...

I might be misunderstanding you, but this definitely doesn't apply everywhere.

I don't know how this works in the rest of the world, but in the Netherlands at least my dishwasher is only hooked up to the cold water, running my tap will have no effect on the temperature of the water my dishwasher receives.

I bought a new dishwasher (and it's not as good as the old one :/), in the instruction manual it says you can use some configuration to tell it it's hooked up to hot water.

It makes sense to hook it up to a hot water line, given things like solar collectors and heat exchangers heating / pre-heating water.

I can't speak for every person's experience, but what I believe is that most dishwashers being sold today, anywhere, are capable of being connected to domestic hot water, or cold water. They will work with both. That's not the same thing as saying every dishwasher being sold can do this, but check your instruction manual. Perhaps it can. As per a sibling comment, decide holistically if that would be a good idea or not.

Unless someone can point me to the existence of regulations saying something like "it's illegal to connect a dishwasher to a hot water line, it's gotta be cold water that the dishwasher heats up itself", then my expectation is that most dishwashers can be connected to either hot or cold, and will heat the water to the correct temperature.

Looking at EU regulations, as far as I can see, they don't regulate the intake temperatures that dishwashers have to accept. What they do regulate is energy usage labelling, and mandating there must be an "eco" mode, what the eco mode must do, and if you get to select multiple modes then "eco" mode must be the default. https://commission.europa.eu/energy-climate-change-environme...

> I can't speak for every person's experience, but what I believe is that most dishwashers being sold today, anywhere, are capable of being connected to domestic hot water, or cold water. They will work with both.

This is not my experience. Nowadays appliances such as washing machines and dishwashers, in Europe at least, only have a cold water inlet.

Apparently modern appliances use so little water overall that it's no longer efficient to connect them to a hot water supply, since they will stop drawing water before the hot water runs through the pipes, and therefore it just wastes the hot water.

Many European machines accept hot water. Any Miele does, and my entry level Bosch (in UK) accepts up to 60C but you have to set some obscure setting on the machine (the manual explains). But I find even cheap machines wash pretty well even without this, and you are right about it it being hot only if the machine is right next to the boiler.

> Other countries' dishwashers are also connected to the hot water supply.

I think it is more a 110V vs. 230V household power issue. For 110V countries like the US the amps needed to heat up the water would be pretty high or the heat up would take very long. In Europe however I have yet to come across a dish-washer that is connected to the hot water supply.

The US actually has 220V available in most households.

Yes, virtually all US households have 240V service. But virtually none of them have a 240V outlet where the dishwasher goes.

Just a note on the hot water supply: Whether this happens depends on three factors:

- Does the dish washer support it? Not all do in the EU.

- Did the plumber install a warm outlet when they set up the connection for the dish washer?

- Does it even make sense from a holistic perspective?

The latter depends on the specific circumstances. For instance, I live in a country with district heating, and here it makes sense, because then I can use cheap heat. My dish washer supports it. But there's no warm outlet installed by the plumber, and currently the heat is mostly from coal, whereas the electricity is mostly renewable, so for the time being I just let it be.

> Other countries' dishwashers are also connected to the hot water supply.

No? I'm in Germany, all dishwashers I've ever had were connected to cold water and heat their own water.

That's OK, that's your choice. I believe most dishwashers will work with either.

My dishwasher is connected to a hot water tap and also heats its own water to exactly the correct temperature... it just doesn't need to heat it as much because it's connected to a hot water line.

Here's the install guide of a random dishwasher selling in Germany right now: https://media3.bosch-home.com/Documents/9000521334_L.pdf

It says to connect to a water source with these characteristics:

* Pressure: 0,05 - 1 MPa (0,5 - 10 bar) * Temperature: max 60°C

It doesn't specify a minimum temperature although I assume it'd have to be >=1°C. But it is clear you can connect to either a hot or a cold water line.

Sure, it optionally supports it, but that's an extra water line that'd need to be run.

And what for? Whether the instant water heater or the dishwasher heats the water, it's still going to be the same amount of electricity, the same cost.

Have a look at the overview on Geizhals.de - Almost all current models have optional hot water intake nowadays (like 95%+ of the models from AEG/Bosch/Siemens/Neff/Bauknecht/Miele). This is to further advance the energy-rating. Doesnt apply to the cheaper manufacturers though.

981 of 1027 models from a number of well-known brands have an optional hot water intake: https://geizhals.de/?cat=hgeschirr60&xf=1069_AEG+Electrolux%...

Whether you heat the water in the dishwasher or in an instant water heater, it's still going to be the same amount of electricity for the same cost.

I think in the US people might heat water with natural gas, which is cheaper, but that's not really the case in most rental apartments in Germany.

>I don't think this is a US-vs-world issue.

Which country are you in?

I'm in the UK and we only connect dishwashers to the cold supply. Other comments in this thread from NL and DE are the same.

I'm in the UK and have a dishwasher connected to the hot water right now. There is not some country-wide uniform "we".

The manual makes clear this is quite OK.

They work with either hot or cold water. They will heat the water to the temperature they need. They don't work with _too hot_ water, hotter than they would heat it themselves (e.g. >60°C), but that's also outside the range of most domestic hot water supplies (which per BS 8558 should have a draw-off temperature of 50°C at sinks).

As a quick sample, here's the Argos dishwashers page: https://www.argos.co.uk/browse/appliances/dishwashers/c:2961...

Pick any dishwasher at random, go to Specifications -> General -> Water fill. Every single one I picked, all from different manufacturers, said "cold or hot"

Looking at one random choice's data sheet: https://documents.4rgos.it/v1/static/3425118_R_D010

> Maximum temperature for water intake (°C) 60

I wasn't able to find manufacturer recommendations from Argos, but I did find two Swedish manufacturers that support either hot or cold water, but recommend that you use the cold water line. One of them claims that detergents are designed to work better when starting with cold water (presumably this is not the case in the US, where hot-water-only machines are the norm).

> Connect the machine to cold water if possible. Then the dishwasher itself heats up the water during the washing phase and the final rinse, which means that you save about 20 percent of energy. Today's dishwasher detergent works best and tablets dissolve better when the program starts with cold water.

> Dishwashers connected to cold water use around 30 percent less energy than dishwashers connected to hot water. A dishwasher connected to cold water only uses hot water when it is really needed.

https://www.cylinda.se/produktguide/kok/diskmaskiner

https://www.electroluxhome.se/vitvaror/diskmaskin/inspiratio...

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