[twdavis]

Hi,
We remodeled an existing bathroom and also had a new bathroom installed. The bathroom sinks are back to back to the same wall. The original 1 1/2 inch air vent was replaced with a new 4 inch air vent. Both bathroom sinks now have dual lavatories with a common drain line. The dual lavatories in each bathroom are connected to a "T" connection which then goes into the main drain line.

The problem is whenever water is run in either bathroom sink, there is a "glug glug glug" sound as the water drains. Very annoying for the wife.

From what I have read it has to do with the air vent.

What options do I have?

[speedball1]

A gurgle tells you that the lavatory's venting throgh the trap and not the vent pipe. The sound you hear is air being pulled the water in the trap.
It sounds like the two lavatories aren't connect to the outside vent. Go back and check your connections. Good luck, Tom