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Comment by superseeplus | Hacker News Reader

Most dishwashers are connected to hot water. Some higher end dishwashers can work with cold water, but the cheaper ones don’t. Does this mean using a dishwasher is a problem as well?

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This must be a US-centric thing, having had many dishwashers in my time and having never seen one with anything other than a cold water inlet.

I assume this is related to the availability of 230v/15A for the heater element.

Must be. I'd say most dishwashers are connected to the mains supply and not pre heated.

If you have hot water, why wouldn't you use that for the water connection?

My dishwasher has a heating element, but the colder the water is, the more it has to work.

So if it's cheaper to use gas-powered hot water from the boiler than to heat it electrically, why wouldn't you? And it's there in the kitchen right next to the sink which has hot water available anyways, so it's kind of a no-brainer.

Yes, I'm in the US -- you can see on a kind of average dishwasher installation manual [1], it specifically instructs you to connect it to a hot water line.

[1] https://www.whirlpool.com/content/dam/global/documents/20101...

My dishwasher uses sufficiently little water that it would get mostly cold water from the hot water pipe.

Yeah, the standard advice is actually to run your kitchen faucet on hot until you get hot water, before you start the dishwasher.

I'm always rinsing off the bigger gunks of food with hot water anyways as I load the dishwasher, so it's hot already.

At the end of the day it doesn't matter that much. The main point is just, if you have hot water available, it's hard to see why you wouldn't take advantage of that.

I’d assume that wasting a lot of hot water before running the dishwasher negates any price benefits from heating the water with gas instead of electricity. Not to mention the CO2.

> If you have hot water, why wouldn't you use that for the water connection?

Two protein related reasons: hot water can denature detergent enzymes making them less effective, and hot water can cause food proteins on the dishes to harden and set.

European manufacturers claim that detergents work better when starting the program with cold water, and recommend doing so. The situation might be different in the US, where using the hot water seems to be the norm.

Probably not. Most of the water runs off the dishes. A very thin film remains that evaporates in the dry cycle, and even at that a lot of it will bead up and run off completely.

I have found that new dishwashers with good eco ratings leave easily detectable amounts of soap on the dishes. Even apart from any health impact, I make it a point to never use them on their default eco programming, but switch to sth that uses more water. I want my dishes clean, that includes soap residue.

I got rid of a perfectly fine 35 yo dishwasher that cleaned fine even without soap, due to heat and water use. I got rid of it because it was loud, but I always wondered if running it without soap was perhaps not as eco friendly as a modern washine using less heat and water.

Use less soap. I use about half as much and the dishes come out fine. I've had better luck with liquid based soaps too as they mix immediately with the water.

You cut those tablets up?

I don't use those, I use liquid dishwashing gel.

Sounds like you're probably using too much detergent.

There's only tablets, how can you use less? Even those that they recommend have this.

The tablets are popular but at least here you can still get liquid or powder detergent for automatic dishwashers.

Havent seen those in over a decade.

What country do you live in?

Buy powder or liquid instead?

I use either Cascade powder or the Walmart brand equivalent and only put a teaspoon or so of powder in the cup per load and a few dozen granules of powder on the door for the prewash.

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