This could be a blockage in the main DWV (drain, waste, vent) pipe which is usually a 4" pipe from the upstairs toilet and passing by the downstairs toilet, presuming the one is directly above the other. The other drains (sinks, showers, etc.), are smaller (1 1/2" or 2") and might be tied in below the blockage in the main stack and are therefore not affected. In this case, you could remove a toilet and run a plumber's snake or drain auger down the main stack to remove the blockage.
This blockage, however, could also be in the drain going to the street, since these are often blocked by tree roots growing through the tiles or pipes. The smaller drains are not affected because of the small amount of water which seeps through the blockage, whereas the large rush of water from a toilet, will back up easily. To correct this problem, you will need a power auger designed to cut through roots and this auger can be run through the main cleanout towards the street. These are available at rental shops.
Otherwise, hire a plumber :)
The drain from the toilet to the main drain is plugged and the branch to the shower is not. If the main floor toilet flushes, it is between the two toilets and not between the house and the sewer.
anticlockwise. (All toilets in the Northern Hemisphere flush clockwise, all toilets in Southern Hemisphere flush anticlockwise.)
If your plumbing system is properly installed there should not be any problem. If it isn't installed properly, you would already have water from sinks and bathtubs backing up out of the downstairs toilet.
pressure regulator valve
low flush toilets use less water.
Yes
No
pit toilets, composting toilets, pour-flush latrine, cistern-flush toilet, bucket latrine
It depends on what type of flush you use. Old style single flush toilets use around 11 litres of water per flush, older dual flush toilets use 4.5 or 9 litres per flush, while modern water efficient dual flush toilets use 3 or 6 litres per flush.
Toilets to flush clockwise in the north. However, it is not due to the rotation of the earth as many people believe. It is because of the way water is jetted into them.
Yes, but not in the way we think of flushing toilets. In private houses, a bucket or two of water was used to flush away the waste and prevent odor. In the public toilets latrines, there was a stream of running water beneath the seats to flush away waste.
no