You must have a leak somewhere. If you are on a well check the pressure tank, make sure there is adequate air pressure. ( check at nipple on top, should be in excess of 25 psi) Check the pipe to well. Listen carefully at the well while pump is running. If there is a leak in the down pipe or lower check valve you will hear water hissing.
If none of these ideas work, post again and be more specific about your system.
because you removed water from the system
With no air in the system anywhere, there would be nothing to hold pressure, so the slightest leak would cause the system to go to zero.
it depends how long you leave the tap on for and what pressure the water is coming out at. e.g. if the water pressure is 5litres per second and you leave it running for 30 seconds, then 5 * 30 = 150litres would come out.
The water would have the same density anywhere it is.
Water creates pressure when it is present in the body. Lowering the amount of water in the blood through diuretics lowers blood pressure. Think of a garden hose with water running through it. If you shut off the end where the spout is, the pressure will increase in the hose, if you open it an let the water run out, the pressure inside the hose will drop. The same principle works in your body. If you have less water in it, by urinating more, your blood pressure would drop.
Fluctuations in city water pressure. Sometimes this is a bad toilet ballcock. Test by turning water off to one toilet at a time to see if it stops.
Davey Pressure Booster Systems with Torrium® control technology would help increase the water pressure from a city water system.
When my water pump went on mine, my car would constantly overheat for no reason, there is a safety valve on the pump which lets coolant out of it when the car is running and pressure builds up. You have it pressure tested, the water pump will normally leak externally under pressure.
Think of it this way, if you had a plastic bottle filled with water and you poked a hole in the side, would water squirt out or would air squirt in? If air squirted in, then the air pressure would have to be higher. But since we know that the water would squirt out, we know that the water's pressure must be stronger. Of course, this is under normal conditions. If you pumped the air pressure up enough, then the air pressure may become stronger than standard water pressure. So actually, water pressure is generally stronger than air pressure.
The answer would depend on the pressure attained by the cooker.
first I would see if there is hot anywhere. if not the problem is with your water heater. if its electric check your breaker or fuse box. if gas call your friendly plumber
My bet would be the hot water heater cycling water through