I just spilled a glass of water on my computer at approx 11 am. In a flash I turned it upside down and powered it down. It has been standing upside down since then in a warm place in the kitchen. How long should I wait before turning it back on?
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Oh no! Sounds like you did the exact right thing. Turned it upside down, open, with the display hanging off the edge of the table. I like to prop the computer off the table with some small blocks so that air can circulate under the keyboard. The most important step is to place a fan pointing under the keyboard so that air continues to move. Nothing dries water faster than moving air. (years of working on damp mildewed sailboats has taught me that)

I would then wait at least 48 hours. Then cross your fingers and hope for the best. Liquid damage is a killer but water is not as bad as coke/coffee. If you had said anything other than water I would have said forget it. Let me know how it goes.