For thousands of years, the task of bringing fresh water into homes and wastewater out has produced marvels of engineering and ingenuity. Elaborate systems of water collection, storage, and piping have been uncovered in archaeological excavations around the world.
Three thousand years ago, the ancient Cretans even devised a crude flush toilet that used rainwater or cistern water to dispose of the waste. And a more elaborate one that actually had running water was recently uncovered in a two thousand-year-old Chinese tomb. In modern times, good plumbing is often taken for granted, so it is a good idea for any homeowner to understand some of the basics of plumbing.
The two basic parts to any plumbing system are the:
- Water supply system - brings clean water into the home
- Drainage, Waste, and Vent (DWV) system - removes wastewater from the home and prevents the danger of sewage gas seeping back through the pipes into the house.
Plumbers use a combination of water pressure and gravity to obtain these results. All plumbing fixtures are designed to operate under a fixed range of pressure and plumbers must ensure that the proper pressure is maintained for the fixture to work.
Maintaining Proper Water Pressure
Water pressure is controlled by the internal diameter of the pipes. The smaller the diameter, the lower the pressure, and the greater the velocity of the water moving through it. The angle of the pipes controls the effects of gravity.
In order to ensure proper function, there is a standardized system of building codes that controls many aspects of plumbing, including the:
- Internal diameter of pipe that must be used for a particular plumbing section or function
- Amount of slope or downward drop that drain pipes need to function properly.
In most houses, the water supply comes from one of two places:
- A private well
- A service pipe that connects to the city water main.
For houses with private wells, a pump pushes water up into a pressure tank (usually in the basement or crawlspace), where it is stored for use. Houses with city water have a water supply line that is connected to the city's water main. Water passes through a water meter that measures the volume of water used in the house. In case of repairs or emergency, both systems usually have a shut-off valve located near the start of the incoming line that enables the water supply to be temporarily cut off.
Water supply lines are usually made of copper, chlorinated polyvinyl chloride (CPVC) plastic, or galvanized steel. Pipes carrying cold water branch out from the main pipe. Some water is directed to the hot water heater for heating, and hot water pipes originate from there.
Where Does The Wastewater Go?
When wastewater goes down the drain, it first passes through a trap, a U-shaped curve in the pipe that retains a small amount of water so that sewer gas cannot come up through the pipes and enter into your home. Then, it passes into the main waste drain pipes.
The main component of the waste drain is the soil stack, a vertical stack of pipes that is connected to the outbound sewer line. The stack has a vent that extends vertically out through the roof, allowing gases to escape and promoting drain flow by drawing air inward. It is very important to keep this vent clear, as plugged vents can trap dangerous gases and inhibit drainage.
Most new DWV systems use rigid plastic polyvinyl chloride (PVC) or acrylonitrile butadiene styrene (ABS) pipes that are sealed with glue. Older homes generally have had cast iron pipe sealed with lead solder, although some new homes also use cast iron sealed with neoprene in order to avoid the noise plastic creates when water is draining through it.