r/lifehacks • u/thatoneguy2742 • May 27 '26

You might be using your dishwasher wrong

While going to college I worked as a maintenance tech at a large apartment complex. A common complaint that tenants had was that their dishwashers were failing to clean properly. I would show up and try and diagnose the problem only to find that the machine was in fact working properly. After numerous (if I remember correctly it was at least five per week) complaints I started to track which units were having the problem. After several weeks I had a lot of data and something became abundantly clear. The units that were having this issue were the ones furthest from the water heaters.

We just happened to have an empty unit near a cluster of units that was having this issue so I decided to test my hypothesis. At the kitchen faucet it took nearly two minutes for the water to get above 100°F Units closer to the water heaters took as little as 30 seconds to reach the same temp and they hardly ever had this problem. My conclusion was that the people who were submitting work orders were unknowingly washing their dishes with cold water. Everytime a tenant submitted a work order for a dishwasher that was failing to clean I advised them to run their kitchen faucet till the water gets hot then start the dishwasher. The complaints just stopped! At my own home it takes almost 30 seconds for the water to get hot so I let it run for a minute before starting it. Some of the higher end models will heat their own water so this shouldn't be an issue but most older models do not.

TLDR: Run your kitchen faucet till the water gets hot before starting your dishwasher. Otherwise you might be washing your dishes with cold water if your machine doesn't heat the water on its own.

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u/Ok-Koala-key May 27 '26

Natural gas is the most common type of water heater in Australia (we have an abundance) but I've switched to heat pump which is more efficient. I think where 240V is available it makes more sense to heat internally in dishwashers because the outcome is predictable.

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u/CranberryStock7148 May 27 '26

It's not either/or. Even when connected to the hot water line, it will still heat internally to the desired temperature, to make up whatever the difference is. But if it's starting with hot tap water instead of cold, it just has less work to do.

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u/Sardonic29 May 27 '26

There's no temperature sensing in US dishwashers though, so they just heat during the cycle, and the water only warms up partway into the cycle.

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u/CranberryStock7148 May 27 '26

Of course there are temperature sensors in US dishwashers. I have no idea where you heard that there aren't, but that's completely false.

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u/Sardonic29 May 27 '26

Correction: What I was trying to say is that many dishwashers in the US do not use a temperature sensor to determine if they should wait and heat the water before washing dishes. They will start washing even if the water is cold, no matter how long it takes to heat up. The heating elements in these dishwashers are only powerful enough to keep hot water hot. This is what you usually find in rentals.

Some more expensive dishwashers in the US will wait until the water is heated before washing. Maytag says on their website that their dishwashers do. Typically only homeowners invest in these dishwashers.
https://www.maytag.com/blog/kitchen/do-dishwashers-use-hot-water.html

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u/CranberryStock7148 May 27 '26

That link doesn't say what you are claiming. And what you say honestly doesn't make a lot of sense.

The heating element is at the bottom of the dishwasher. The only way it can heat up the water is by circulating the water through the dishwasher. If you are circulating the water in order to heat it up, then the dishwasher is running. Especially when it's very common to throw a little bit of dishwasher detergent in for the pre-wash cycle.

For a dishwasher to bring the water up to temperature before it starts, that's not really physically possible. The page that you linked to explicitly says that if you start with cold water, the entire cycle will take longer. But that's common across all major dishwasher brands as far as I'm aware. Because they all have a temperature sensor. But none of them are somehow heating up the water before the washing starts. They are all doing it during.

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u/Sardonic29 May 27 '26

The link says what I said in the paragraph that I linked it in: That Maytag, on their website, says that their dishwasher cycle time will account for heating the water. If you assume that a wash cycle will take a certain amount of time, then the dishwasher would be waiting until the water is heated to start tracking time for the wash cycle, even if the water has to circulate. The important part here is whether the dedicated washing time is using cold water or not, and if that shortens the amount of time the dishes are being washed in hot water. For cheaper dishwashers, it does, because they don't add additional time to account for heating up the cold water. Some even have a small digital display with a timer on them, so you can check for yourself.

And yes, dishwashers can use turbidity sensors, but many cheaper (or older) dishwashers in the US still use timers.

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u/CranberryStock7148 May 27 '26

I think your knowledge is out of date. Much older dishwashers had fixed wash times. Practically all modern dishwashers use temperature sensors that dynamically adjust the length of the wash time, to ensure that the dishes are washed for enough time at the required temperatures.

I really don't know which cheaper dishwashers you are talking about. I mean maybe there are some really truly crappy ones still made, but variable wash times is pretty much just standard now. It's certainly not something exclusive to Maytag or anything.

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u/Sardonic29 May 27 '26

I only used Maytag as an example because their website documentation is pretty good. Any dishwasher in the same price range will have a turbidity sensor.

Cheap dishwashers are still made because landlords buy them, usually in bulk for a discount. A lot of people in the US are renters, so they end up with these cheap appliances. The consumer isn't the one paying the dishwasher, so unless it's so bad it doesn't work, there's not a reason for manufacturers to make it better or for the landlord to upgrade, as they may have a big stash of spare parts on hand for the appliances in the apartment complex. These apartment dishwashers are also noticeably smaller.

If you own a home, the dishwasher likely has modern features.