On most push/pull stoppers the knob part that you pull on unscrews from the stopper, and under that is a slot for a screwdriver tighten or remove the stopper. On stoppers with non-removable knobs, there is a screw (usually phillips) under the stopper which can be accessed with the stopper in the up position and unscrewed to remove the stopper.
If you mean 'transmission drain plug', there isn't one. You must remove the pan to drain fluid. Be careful, and have a large paint tray or similar because as soon as the bolts are loose, fluid will come out.
Drain the fluid from the reservoir. Reservoir drain tube. Remove the wiper reservoir retaining bolts. The wiper reservoir will come off.
The bottom part of the engine is the oil pan. There will be a drain plug on it, remove drain plug and oil will come out; properly dispose of oil.
Go and see your piercer
perhaps it is water from the air conditioner, sometimes the drain hoses come loose.
Drain cleaner or a snake. If you use a snake, take the overflow plate off on the side of the tub above the drain and go down from there. That saves making the sharp bend if you go through the drain itself. It may be hair wrapped around the drain shut off which will come out when you remove it from the overflow tube.
There is usually a drain plug on the bottom, release this and the water will come out.
Drain the water from your Corvette radiator. Remove the radiator hoses. Remove the radiator stabilizing arm bolt. Remove the radiator retaining bolts. The radiator will come off.
Check the trunk light is not staying on, the switch on the the hinge may have come loose and is not shutting off the light.
The toilet flange is usually above the floor level. You would have to cut it off the drain pipe and cap it. How you do this depends on what type of pipe the drain is made of. Even if the drain should be below the floor level, you have to seal the drain or sewer gas will come up from the drain.
To connect a washing machine drain hose to a flexible hose it is proper to seal the union with plumbers tape and a hose clamp. Silicone should not be used because it may come loose and get into the drainage system. If Silicone is used it might also be necessary to cut the hose when removing the washer drain hose.
You will need to drain the water from your cooling system. Remove the water pump belt. Remove the water pump retaining bolts. The water pump will come off.