Why do your drains gurgle when they drain?

They gurgle because of the sudden release of air.

You have this gurgle because your vent pipes are either stopped up, in the wrong place, or are iadequate in size. When you drain water the you put pressure on the air in the drain lines. This pressure is actually sewage gas and should go out through your vent stack(s). You will need to repair or reppace your vents for this problem to be corrected.