What could be causing water to back up from under one toilet, bubbling in another when water is draining from washing machine or bath tub?

Hi Berry

It sounds like a partial blockage in your main drain line.

If you guys are handy and have good mechanical skills you may be able to rent a snake from a local home depot or tool rental store and snake the drain yourself. Otherwise, you need to call a plumber and have him/her snake the drain line... *UGH*!

An important thing to note here is that you probably aren't having any issues until you use the high volume fixtures such as the washing machine or draining of a full tub. This indicator is what leads me to suggest a PARTIAL blockage instead a complete blockage, OK?

You'll also need to plan on installing a new wax ring at the toilet that has water coming out from the underside as the seal between the toilet bowl and the toilet flange has broken down and will need to be fixed.

Any more questions just let me know, OK?

Mark

Blocked sewer line, snake sewer line.

Wax rings aren't there ton prevent water from backing up over the horn on the bowl, However, the other experts are correct. You have a blockage in your line that must be snaked out. This can be done by pulling the toilet and snaking from there or snaking from the lavatory roof vent, Good luck, Tom