We have one level home with two baths with tub and shower combined also in laundry room have a toilet and shower. In the kitchen we have no garbage disposal. In the hall bathroom which is the farthest you flush the toilet and it is stopped up and you can here air bubbles coming from the tub. If you do the laundry thirteen feen away still you here the air bubbles. We do have a three inch main septic line under the house. It was that size when we bought it. Is the three inch the right size? Also the air bubbles in the line, does that mean the line is stopped up some where? Thanks, David.