Every time a toilet is flushed (we have 2) or the tub is drained or shower used, or washing machine is draining... there is a GLUG! GLUG! GLUG! SOUND that comes out of the kitchen sink... and it is loud! Also, anytime anything is draining, i.e. tub, toilet, washing machine... sometimes the toilet fills up with water and over flows... We have one toilet that is not fastened tightly to the floor in one bathroom as we just put in a new floor and have not gotten it fastened to the floor yet, or sealed... But this has been going on forever it seems... What could be causing it? We have tried drain cleaner, we have fastened down the toilet (not sealed it) and we had one leak under the mobile home, but got it fixed.. it was a main pipe that had to be replaced for the sewage drain... but it is still making the same noise... PLEASE HELP!

Your drains are not venting properly. Do you see the vent pipe on the roof, rod that pipe with at least a 1/2" snake. Rod from roof top to the lowest point in the home plus 15 ,more feet.