Old style toilets, (many of which are still in use) used up to 22 litres. New toilets are set to 13 litres, many with a 6 litre option.
5 gallons
If you want to use less water per flush, you put a brick in the bottom of the tank. You do not want to reduce the height of the water in the tank so much as use less water per flush.
well this depends how wide and large your bottom is.
Depends on how bad it is leaking
Depends on whether you already purchased it and whether other parts are needed. If you have the toilet, a Kant leak, a wax seal,FLEXIBLE toilet supply, and the (nuts,bolts and washers) for screwing the toilet to the floor flange, plumber should not charge more than one hour of his rate to install it. Make sure the plumber does NOT silicone around the toilet. If there is a leak from the wax seal under the toilet and it is siliconed, the water stays under the toilet and rots the floor, if you are on a wood floor.
If the toilet works each time on one flush, they use roughly half the water of a standard toilet. You would then use half as much a month on the toilet. They do not always flush completely on the first flush and the toilet is only a part of the water bill.
3 liters
You use anywhere from 1 cup of water to 5 cups of water to flush the toilet. This is per time you flush the toilet.
In a modern toilet you use 13 litres per flush.
It takes 1 bucket of water when we flush.
100 Galen
I believe it's 3 gallons
5 gallons
1.6 GPF.
If it's a normal household toilet you simply lower the water level in the tank that's over and behind the toilet by adjusting the fill valve. There are many different designs so I can't tell you how on your particular toilet. Some ae as easy as turning a plastic screw and some are a real pita. If you adjust it and raise the water level too much water may run over into the overflow tube and it will just keep running. If you lower it too much your toilet may not flush completely. Generally I adust mine as high as they will go without overflowing in order to get a stronger flush. I have never needed or wanted to turn down a flush.
There is about four to five gallons wasted if you flush a toilet but I don't believe that it makes a difference if the handle is loose or not. Unless, the toilet is leaking from the handle or somewhere else.
5 gallons