fairly thick and I didn't want to risk clogging older pipes. There are any number of "liquids" you're not supposed to pour down the drain (spoiled milk, for example). I didn't pour anything in the toilet because we have a septic system with limited capacity and a zillion rules (from the township) about what can and cannot go into the toilet. Probably either option would've been fine but I didn't want to risk mucking up the sink or toilet.
Regarding laundry, your dad doing things like throwing a dirty kitchen towel into the dryer with clean clothes and putting your set aside hot pink shirt into the laundry, would be a deal breaker for me. I hope he, at least, used cold water, not hot. IIRC, this is not the first Dad-induced laundry mishap. Canโt you just set some boundaries and create a new rule saying that you do your own laundry? I would insist on it.
I *could* do that...but he usually (almost always) does a great job with the laundry and it makes him happy to help out. The laundry came out fine; it was neither pink nor fragrant with cooking spices. Honestly, I only posted this as a funny story, not problems to be solved.