Someone recently insisted that filling a washing machine to the top doesn't get clothes as clean. My washing machine has water fill levels from "Small" all the way to "Extra Large," but no corresponding lines inside the machine to indicate how high one is supposed to fill the clothes. When I have a lot of clothes, I set it to "Extra Large" and then loosely drop clothes in all the way to the top of the basin.

Here are other examples of the claim:

Whilst it is a good idea to fully fill your washing machine with dirty laundry before using it to save power and water, you should not cram it to overflowing. The clothes will not get clean...

3 / 4 full is best to leave room for clothes to get washed correctly sometimes u will have to do it agin if its too full happy washing.

An overcrowded load will absolutely not come clean (I proved this to myself again just last weekend). Clothes need a certain amount of room in the washer to move around.

I'm interested in knowing whether any experiments have been conducted to evaluate whether some similarly-soiled articles come cleaner in one load size vs. a more filled load size.

I'm explicitly not talking about packing clothes in the washer. I'm simply talking about loosely dropping clothes into a top loading washer until they reach the height of the basin, then closing the door.

  • I'm not sure this question is answerable, as I believe it depends on the washing machine. If I overfill my (current) washer, the spin cycle doesn't work right and the clothes come out soaking wet and soapy. When I had a front loading washer, I was told you can really pack clothes in them.
    – Sam I Am
    Jan 25, 2012 at 3:02
  • 1
    I work for a company that makes washing machines, as well as other home appliances. Years ago I was involved with the labs that test various designs to see how well a new design would perform. The AHAM organization publishes several standard tests used to rate performance and my company has many more of its own. With some types of "dirt" it's better to have a higher water to clothes load ratio and with other types of "dirt" it's better to have a lower water to clothes load ratio. (I'll provide more detail in a real answer later.)
    – oosterwal
    Jun 14, 2012 at 4:21
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    @oosterwal That sounds awesome! I'm looking forward to your answer. Perhaps include some screen shots of graphs/plots for pertinent findings. This sounds quite neat. Thanks.
    – Hendy
    Jun 14, 2012 at 15:33
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    @oosterwal: Are you ready to post that answer?
    – Oddthinking
    Jul 11, 2015 at 2:31
  • 1
    @oosterwal It's been over 6 years! Are you still polishing that answer? Mar 6, 2019 at 15:29


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