4 ms·

This must be a country-specific thing. Almost all dishwashers in Europe use a cold water feed only, so running the hot tap won’t make any difference. (Source:

This must be a country-specific thing. Almost all dishwashers in Europe use a cold water feed only, so running the hot tap won’t make any difference. (Source: bought a new one a couple of years ago! I assumed a hot water feed would be more efficient, but very few models had it and they weren’t necessarily cheaper to run. Thinking about it, an electric heater inside the washer that heats exactly the amount needed is going to be way more efficient than getting hot water at a random temperature from a gas combi boiler.)

baq 5y ago
Mine says using hot water will work but only do it if you have a renewable source of heat. Otherwise, it’s more efficient to just heat up those few liters.
bonestamp2 5y ago
> Almost all dishwashers in Europe use a cold water feed only, so running the hot tap won’t make any difference. Ya, I think the same is true in America. Most residential hot water tanks do not produce potable water. So, it wouldn't make sense to rinse your clean dishes with water that may contain bacteria and spores. Of course, you don't want to rinse hot glass with cold water either (potential breakage), so now you have to heat the water. So, you may as well just have cold water as the only source and heat it. It's the same reason coffee machines tell you to fill them with cold water -- it has nothing to do with the temperature of the water, it's all about the potability of the water.
- spookthesunset 5y ago
  > Most residential hot water tanks do not produce potable water. As a consumer of residential hot water tanks for 40+ years, this is news to me. How is the water in a residential hot water tank not potable?
  - manwe150 5y ago
    I’ve heard: Higher levels of dissolved minerals, which might be harmful, and a low chance of being a breeding ground for brain-eating microbes, which will be harmful.
    - iainmerrick 5y ago
      I think it’s specifically Legionnaire’s disease / legionella. Hot water tanks should periodically be heated over 50C to kill off the bacteria. See e.g. https://www.hse.gov.uk/legionnaires/hot-and-cold-water-storage.htm https://www.hse.gov.uk/legionnaires/hot-and-cold-water-stora...
  - bonestamp2 5y ago
    It was a surprise to me when I first read it about 10 years ago too. I'm having trouble finding the source for the (potential) bacteria breeding problem. But, I did find an EPA document warning not to do it for another reason: https://www.epa.gov/sites/default/files/2015-09/documents/2002_5_17_lcrmr_guidance_lcmr_lead_public_education_poster_v1.pdf https://www.epa.gov/sites/default/files/2015-09/documents/20...

baq 5y ago

Mine says using hot water will work but only do it if you have a renewable source of heat. Otherwise, it’s more efficient to just heat up those few liters.

bonestamp2 5y ago

> Almost all dishwashers in Europe use a cold water feed only, so running the hot tap won’t make any difference. Ya, I think the same is true in America. Most residential hot water tanks do not produce potable water. So, it wouldn't make sense to rinse your clean dishes with water that may contain bacteria and spores. Of course, you don't want to rinse hot glass with cold water either (potential breakage), so now you have to heat the water. So, you may as well just have cold water as the only source and heat it. It's the same reason coffee machines tell you to fill them with cold water -- it has nothing to do with the temperature of the water, it's all about the potability of the water.

spookthesunset 5y ago
> Most residential hot water tanks do not produce potable water. As a consumer of residential hot water tanks for 40+ years, this is news to me. How is the water in a residential hot water tank not potable?
- manwe150 5y ago
  I’ve heard: Higher levels of dissolved minerals, which might be harmful, and a low chance of being a breeding ground for brain-eating microbes, which will be harmful.
  - iainmerrick 5y ago
    I think it’s specifically Legionnaire’s disease / legionella. Hot water tanks should periodically be heated over 50C to kill off the bacteria. See e.g. https://www.hse.gov.uk/legionnaires/hot-and-cold-water-storage.htm https://www.hse.gov.uk/legionnaires/hot-and-cold-water-stora...
- bonestamp2 5y ago
  It was a surprise to me when I first read it about 10 years ago too. I'm having trouble finding the source for the (potential) bacteria breeding problem. But, I did find an EPA document warning not to do it for another reason: https://www.epa.gov/sites/default/files/2015-09/documents/2002_5_17_lcrmr_guidance_lcmr_lead_public_education_poster_v1.pdf https://www.epa.gov/sites/default/files/2015-09/documents/20...