One day I was sitting in my living room and I heard a weird sound and all the water in my toilet sink and bath tub drains emptied all at once why would this happen

This sounds like you could have had a plugged vent. If a vent get plugged and there is water going down a drain anywhere in your house it will create a vacuum. This vacuum can be strong enough to pull water out of toilet bowls or sink traps. I take it this was a one time occurence and everything drains properly now?

Describe the sound. Was it a gurgle?

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all the water in my toilet sink and bath tub drains emptied all at once

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For that to happen, both the bathtub and the vanity would have to be clogged with water in the tub and bowl and the stoppers open. If the clog opened up and the fixtures drained then That would give you the situation that you describe. Are there any for the developments? Back to you, Tom