Blocked or dirty pipes. id call a plummer ASAP.:)
Check for the drain hose or pipe in your unit so that it is not clogged. Through the ac process water is collected and thus needs to come out. If the drain is clogged water will be trapped and the blower will pick it up and send it through the vents.
BAD venting causing negative pressure / back siphoning
You can completely drain just do not leave empty for very many days or it may float like a boat.If you have a dew drain water will continue to come back into the pool from the main drain if the water table is high enough.
when your engine is hot it causes the water to boil and the water and the anti freeze will come out of the overflow pipe.
The drain from the washer to the main line is getting plugged and the floor drain is easier. Drain cleaner in the floor drain should take care of it.
There is usually a drain plug on the bottom, release this and the water will come out.
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.
A drain basin is an area of land where rain water and melting snow come together to drain into larger bodies of water such as rivers, lakes, reservoirs and eventually the ocean.
You have a blown head gasket.
The main drain is plugged. Not completely, but enough that it is easier for the upstairs water to come out in the shower and floor drain instead of going out the drain.
Water for clouds typically comes from evaporation of water on the Earth's surface, such as from oceans, lakes, and rivers. The sun's heat causes water to evaporate and rise into the atmosphere where it cools and forms clouds through condensation.
The garbage disposal water may come back up due to a clog in the drain pipe or a malfunction in the disposal unit itself. This can cause water to back up and not drain properly. It is important to address the issue promptly to prevent further damage.