According to Simply Good Stuff, dirty residue in a washing machine is usually caused by either insufficient cleaning or mechanical failure. Simply Good Stuff notes that better cleaning, as well as vigilant inspection of the washing machine, can help eliminate dirty residue.
While washing machines are designed to wash out dirt and soil, build-up occurs in the hoses, pump and tub. This build-up typically comes from hard water and detergents used to wash clothes, and it may be building up every time the washing machine is used. Simply Good Stuff points out that this build-up keeps the washing machine from performing properly, leading to even more build-up of dirty residue. Additionally, abrasive minerals may accumulate along with the residue, making clothes wear out faster. The washing machine can be cleaned by running a hot cycle with two cups of vinegar, which loosens residue and cleans both the fabric softener receptacle and the bleach dispenser.
According to Simply Good Stuff, mechanical failure can also contribute to build-ups of dirty residue. Hoses must be checked for signs of extreme wear or leaks, as damaged or worn hoses can also lead to the washing machine not performing correctly. The typical manufacturer recommendation is to replace these hoses every 5 years.