Bad Ideas - Laundry
Washing
Washing with no detergent
Causes grease & dirt deposits inside the machine, leading to ineffective washes and bad smells.
Ecoballs
Same as above
Never using powder
Scum builds up faster when liquid without powder is used
Never doing a hot wash
Hot washes are needed to clean the machine itself
Using washing up liquid as machine detergent
Soap residue creates scum in the machine. Scum attracts dirt and causes bad smells.
Never descaling
Scale prevents dirt removal and blocks water level sensor tube. Scale is the prime cause of washing machine floods.
Low spin speed machine
Leaves lots of water in the clothes, causing long drying times. And if dried indoors, damp problems. And if tumble dried, unnecessary electricity costs.
Bleach
Standard chlorine bleach makes some plastics brittle, and should not be used in WMs
Top loading vertical axis machines
Use vast quantities of water and electricity compared to modern horizontal axis front loading machines. If you need greater laundry capacity, get yourself 2 front loaders and stack them. Several advantages to this option.
Drying
Draping wet clothes around the house
Drying clothes indoors releases all their water content into the atmosphere. When windows are closed in winter, high indoor RH generally causes condensation, which often causes damp, mould and rot. The more washing is dried this way, and the lower the washing machine's spin speed, the worse the problem will be.