Plumbing. It's something we live with every day and that water is just right there whenever we turn on the tap. Does anyone give how it gets there and how it leaves again a second thought?
Water enters our home via the mains. The mains are located underneath the street where you live and branch out to accommodate each home; every house has its own feed from the main. The water is always cold in the mains and comes into your house via the water meter so they can keep track of how much you are using. Once in the house, the water branches off. Some goes to the hot water tank where it is then heated for use within the home and some stays cold. Both enter copper pipes to move around the vast plumbing network we have within our walls.
Hot water will then travel to those plumbing fixtures that need it to operate, the washing machine, the kitchen sink, the bathroom sink and tub, etc. If cold water is also needed in those fixtures, it will arrive in its own copper pipe and two pipes will feed into the fixture. If the item only uses cold water, like the toilet or the fridge ice maker and water dispenser, then only one pipe will lead to it.
Once used, water then travels down the drain. Just beyond the plug hole or just after a toilet flushes you will notice a U shaped pipe that acts as a trap. This is to ensure some water stays in the pipe close to the fixture so that sewer gas does not travel up the pipe and into you house. When the drain is opened again or the toilet flushed again, the water will move along and new water will take its place.
The drains in your home work with gravity, so all pipes lead to the one vertical drain pipe that whisks used water out of the dwelling. The sewer pipes are also located under the street and each home will have a feed to it. The water then moves along to the sewage treatment plant.
Thinking of the plumbing system as a big circle is an easy way to envision what goes on when you turn on the tap. The water comes in from the street, goes around your home in pipes, is used and then escapes back into the street where it will continue its journey.