Plumbing principles have not changed in thousands of years. While technology has, the principles are the same.

Typically you have a water source, be it a private sources, such as a well or a public source, often provided by local government. Both water sources have their pros & cons. Government sources often treat their water by adding chemicals to kill bacteria, private sources will often use filters and conditioners to eliminate problems, because of the later method, I find that private sources often have a better quality of water. Private sources should always be tested to ensure their are no dangerous bacteria.

With your source in place, the water is directed into the house where upon it is often split to the water heater and throughout the house to the required fixtures.

The hot water heater utilizes either gas or electric to heat the water. It is at this location where you determine the temperature of your hot water. One should take care when setting the temperature, especially when children and the elderly are a primary concern. 

From there the hot water will be piped to all fixtures that require hot water. Not all fixtures will require hot water, such as your toilets and exterior faucets.

Most water lines are 3/4 - 1 inch in diameter. Lines that feed to the fixtures are typically 1/2 inch. Lines are reduced to maintain pressure.

Once the water reaches the desired fixture, it must also be disposed. Disposal of the water / waste will also go to either a private source - septic system or a public source - government waste system.  Again each of these has its own unique pros and cons.

It is gravity and vent stacks (keeps the pipes from creating vacuum) that allows the waste / water to be taken away from the house. It is for this reason that waste pipes must have a downward slope and vent stacks be installed in order this this system to work.

Think of what happens when you hold your finger over the end of a straw that is full of water, when you release your finger the vacuum is broken and the water flows out.

Waste and drain pipes will build up gases that can infiltrate the house. In order to keep these gases from entering the house, "traps" are installed. Traps are often no more then a "U-shaped" water filled fitting that prevents the gas from leaking back into the house.

Most plumbing problems have to do with leaks. Many of these leaks are often the result of the homeowner inadvertently bumping a drain pipe, usually under the kitchen or bathroom sink, or  crimps / connectors improperly installed or failing, and in some cases bad material.

Some of the most common materials that are used are;

Galvanized Steel (gray in color)

Galvanized was in use until the early 60's. There is still some in service in older homes. The interior surfaces of this pipe corrodes over time and the flakey buildup reduces the water flow. Or the pipe will simply rust through and leak. Sometimes it is difficult to run more than one fixture at a time. Typical life expectancy of galvanized steel is 40 years.

Copper (copper / brown in color)

Used from the early 60's and on, copper is the more reliable (and more expensive) material. Copper's one drawback is that it will split when frozen. Also the soldered connections contained lead until about 1988. Copper is still used today, even though most homes are plumbed with the newer (and cheaper) types of plastic piping.

Polybutylene (gray in color)

Most homes built from the late 70's to the mid 90's were plumbed with Polybutlene. PB, considered problematic, is often referred to as "Quest," which is one brand of PB. For more information about the problems with PB, click here.

Acrylonitrile Butadiene Styrene / ABS   (Black in color)

 Used for drain and vent lines.
 

Chlorinated Polyvinyl Chloride (CPVC) (creamy white in color)

CPVC is less expensive and easier to install than copper, but will also split when frozen. It is more reliable than PB.

White PVC (Polyvinyl Chloride, NOT CPVC) is the most common pipe for drains.

Cross Linked Polyethylene (PEX) (red, white or blue)

PEX is the current pipe of choice. It is less expensive than copper. It installs almost exactly like PB, and has been used since about 1995. The pipe has been in use in Europe for many years without any known problems.

Plumbing can be performed by a homeowner, however it is best to leave this to a professional. They have the knowledge and experience to design the plumbing system in a more efficient and professional manner.

Blue indicates cold water, red hot.

Lines are reduced to keep pressure maintained.

U-shaped trap filled with water prevents gas from flowing back into the house.