Partially obstructed drain or vent line. Could also be improperly tied into the toilet drain/vent. In most codes wet venting for more than 1 fixture unit (i.e. a sink) is illegal. Washing machines have their own section of code due to suds relief, air breaks, and the fact that they discharge a large amount of water into the drainage system very quickly.
The pipes are croosed or conected to the hose.GET A PLUMBER!
Improper venting.
The drain is getting plugged and the toilet is lower than the washing machine drain so it is easier for the water to come up in the toilet than to go straight out the drain. Put some drain cleaner down the drain where the washing machine drains and that may solve the problem.
It might be plumbed wrong -- or either your sewer is stoping up --
Sounds like the washing machine discharge is fitted to the main drain in the wrong place and it's discharge is filling your toilet. It's possible there may be something of a blockage just after the toilet, causing a backup. I would try to snake the the pipe from toilet out. You may even have to remove the toilet from the floor and do it there if there is no access underneath (like a basement or a crawlspace). I have snaked main drains from the toilets many times, and it's a pain having to re-re the toilet, but often it's the only way.
You need your septic tank cleaned out.
shower toilet washing hands dishwasher washing machine washing dishes (in sink) washing dog watering garden drinking cooking swimming pool bath
the ocean. All drains lead to the ocean
Use a shower instead of a bath Buy a new toilet if you have an old toilet Turn the taps off if they are not needed Fill the washing machine to the top
tv, refridgerator, toilet, stove, computer, washing machine, phone
Mainline stoppage.
I have seen both.
The drain is plugged somewhat between the upstairs and downstairs. Need to snake the drains.