You will probably notice it from the doorway before you notice it from anywhere else. The laundry basket in the hall has a towel on top that was not there last visit, and the one by the dryer has been there so long it has become furniture.
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Nobody in your family did the washing out of carelessness. For years someone in that house kept a rhythm of sheets on Monday, towels on Thursday, and your father's work shirts ironed without anyone asking. When that rhythm stopped, nothing dramatic happened. The clean clothes just got quieter and fewer, and the house started running on whatever was left.
How to tell it has become the problem
Look for the small things. He wears the same shirt two days running and says it is fine. The bath towels are damp and stacked, not hung. There is a sock in the dryer you found on your last visit. The basket has a second layer on top, which means the first layer never went anywhere. Ask him when he last ran a load, and watch the answer. If he has to think about it, that is information.
Other signs are less about the clothes and more about him. If he has stopped changing the sheets, he may also have stopped sleeping in the bed. If the laundry is stuck, a lot else probably is too. Do not treat the laundry as the whole story, but do not walk past it either.
What to check before you decide anything
Start with the machine itself. Is the washer working, is the dryer lint trap clean, does the hose still fit? A machine that is broken can look exactly like a man who has stopped caring. Find out whether he knows the settings, where the detergent lives, and whether the cabinet is still stocked. If the detergent sits on a shelf he cannot reach comfortably, move it. Small changes like this count for more than a long talk.
Then decide what you want back. Clean towels? Shirts he can wear to a dinner with friends? Sheets he will actually sleep on? Pick one and name it to him. 'I need the towels washed before Sunday' is easier to hear than 'the house is a mess.'
What to do tonight
Count the baskets. Ask him one question about the week ahead: which clothes does he need clean by Thursday? Then run one load together, or start it for him and leave him to fold. Folding is where he will likely want to talk, so let him do most of it. Leave the hall basket empty on your way out if you can, and write down what you did so the next visit does not start from zero.
If the chore has simply become too much, that is a sign to think about a regular plan, not a one-time rescue. The guide to the first weeks on this site, Start Here: The First Hundred Days, covers how to share household jobs without making him feel graded.