If sewage is coming back into a tub, shower, or floor drain, stop laundry, dishwashers, and long showers. More water makes a backup worse. Keep people and pets away from the wet area.
Call a company on this list and say you have a backup. Ask if they can come today and whether they pump house tanks. If the house uses an aerobic system and the alarm is on, you may also need an installer — that is the sister site, not this roster.
Do not open the tank yourself if you do not know the lid location or the gases involved. Do not pour chemicals down the drain as a fix. Pumping removes the solids; it does not replace a broken field or a failed aerator.
After the tank is emptied, ask what they saw. A full tank on a normal schedule is one story. A tank that filled too fast, or a field that will not take water, is another. Keep the notes with the house.
General information for Oklahoma homeowners, not legal advice and not a booking. Compare companies on the directory and confirm the job directly.