What would cause a sink To gurgle?

When you open a sink drain or flush a toilet, a head of water enters the waste pipe. Since it fills the pipe, the water pushes air in front of it and creates a vacuum behind. The vacuum exerts considerable internal force on the pipes, and unless you provide a vent so more air can come in and fill it, the air will enter through any available opening -- usually a sink, shower or tub P-trap. The gurgling sound you hear from your sink is the sound of air rushing past the water standing in the sink or in the bottom of the trap.

That gurgling sound in your sink means there is an issue with the air in the drain pipes. Air normally is supplied through the vents, so either the vents are blocked, or they weren't correctly installed. If the gurgling happens only when you use the sink, you probably should focus on the sink vents, but if it happens when you flush a toilet or drain the tub, you need to examine the entire vent system.If the gurgling happens only when you drain the sink, there's probably a problem with the venting for that sink. The vent may not have been installed the correct distance from the P-trap, or it may be blocked. Immediately call A-General Plumbing company to resolve the issue.