My wife has me remodeling the bathroom in our very small '70's farmhouse. I had to move toilet location about 4' from its original position. After drain lines and water supply lines were reconected there is a very loud gurgleing noise in kitchen sink drain (about 10' away) when toilet is flushed. Kitchen sink drains into 3" drain line just after the toilet inlet. I think the toilet drain water is sucking the water and air out of kitchen drain as it flushes.
Is this a venting problem? The old house has 1 stack but it comes after all drains are fed into main line. I would like to fix this problem without cutting another hole in my new roof.