Re: Drain makes noise when toilet is flushed
jellyjar .... you hadn't mentioned which drain is gurling.
Usually a vent issue would cause a gurgle sound from the sink or tub when the toilet is flushed as it will try and draw air from wherever it can.
If it's one of those .... then like Ravens53 mentioned check the vent for a blockage.
There may also be another unusual cause ... a partial blockage for the toilet.
What's happening is when the toilet is flushed there is a volume of air in the drain sending a bubble of air ahead of the discharge. When this hits a blockage this air bubble bounces back . In cases this will show as bubbles in the bowl when flushed .... but ..... depending if the other drains are tied in after the toilet the air may be coming back up a drain trap and bubbling the water in the trap .... making a sound similar to gurling.
A simple test would be to disconnect the trap from the sink .... flush the toilet to see if the situation improves. What this would do is provide an open direct vent. If you feel air being pushed out .... it might be an indication of the air bubble theory ..... if you feel the air being drawn in would indicate likely a vent problem.
If the toilet is showing any signs of slow draining would be a clear indication of a larger blockage .... perhaps something lodged in the toilet siphon trap or something further down the line.
Which may be resolved with a toilet auger or the removal of the toilet and fishing out the obstruction .... or .... snaking out the drain line.
Hope this helps.
"" an ounce of perception -- a pound of obscure "