If the water level doesn’t start to drop after about a hour, continue to hold the float while you shut off the water at the toilet supply valve, situated near the floor or in the wall behind the toilet, but close it by turning it clockwise
Overflowing toilets require quick thinking & quick action, then it’s not difficult to take care of it if you assume how! Remove the lid from the toilet tank rapidly & carefully & set it aside, but place it anywhere secure, however do not worry about laying it on towels or anything like that; Remember, you don’t have much time to lose! Next, press down on the flapper valve inside the toilet tank, you do not need to worry about the sanitary conditions of the tank’s water! The flapper is the rubber piece in the center of the tank’s bottom, however by doing this, you should be able to prevent more water from entering the bowl & from overflowing, and lift up on the float that operates the tank fill valve once you’ve secured the flapper valve! As the main water supply is shut off, the water level in the bowl should slowly decrease. After about a hour, when the water level returns to normal, you can let go of the float & let the bowl refill without worrying about it overflowing! Keep an eye on it so you can stop it if the level increases. If the water level doesn’t start to drop after about a hour, continue to hold the float while you shut off the water at the toilet supply valve, situated near the floor or in the wall behind the toilet, but close it by turning it clockwise. If you can’t reach the valve while holding the float, let go of the ball & close the valve as fast as you can, then stop using all plumbing fixtures as soon as the toilet stops overflowing & use a plunger to see if you can clear the blockage. If only 1 toilet is blocked, the complication is most likely just with that toilet, then however, if more than 1 toilet is affected, you may have a blocked system drain or a failing septic system.