When you turn on a tap or flush a toilet, plumbing systems make it possible by using gravity and pressure to deliver water where it’s needed. Understanding how they work can help you avoid many plumbing problems.
Plumbing pipes carry freshwater to faucets, fixtures and appliances, and waste water away to the sewage system or septic tank. They come in a wide range of materials.
Water Supply
The most important part of a plumbing system is the water supply line that brings fresh, clean water into the home and delivers it to fixtures like sinks, showers and toilets. This line usually connects the home to a city water supply pipe or private well.
When water enters a home, it goes through a meter that registers usage and a main shut-off valve that prevents water from flowing into the house in the event of a leak or other problem. The main water line should be regularly inspected and maintained by a professional to ensure it is free from corrosion, damage or other problems that could degrade the quality of the drinking water.
Plumbers use a wide variety of pipes and fittings to create a system that can handle the pressure and temperature conditions in a home’s water supply lines. Copper, galvanized steel and PVC are commonly used materials for this type of piping. For high-pressure areas, such as those found in kitchens, plumbers may also use plastic piping called PEX, which can withstand a higher level of pressure and temperatures and has the added benefit of being more flexible than other types of pipes.
Leaks in water supply lines are very dangerous because they can cause significant property damage and pose health risks. The sensitivity of the water supply system makes it one of the most common sources of leaks and other plumbing problems.
Drainage
Unlike the water supply system, which relies on pressure to push water through pipes, the drainage system uses gravity to get rid of wastewater. This is what most people think of when they hear the term “plumbing.” The drains in your home remove waste from your sinks, toilets and showers into a sewer system that ultimately goes to a treatment plant or the municipal sewage line.
The drainage system consists of a network of pipes that connect to all of your fixtures. These pipes are bigger than the ones in your water supply system and they’re angled downwards to play the role of gravity. This is what keeps your wastewater from backflowing into your fixtures and it’s also what prevents your house from stinking.
The piping in your drainage system is known as drain, waste and vent (DWV). The first segment of pipe that is visible at a fixture is called the p-trap or U-bend. This curved pipe holds standing water and prevents sewage gases from rising into your home. Immediately after this section of pipe is another DWV system that connects your house to the municipal sewer or septic tank. This system is designed to lower the water level in order to serve vegetation, and the piping can be made of clay, cast iron or plastic.
Venting
The drainage and vent systems work together to make sure water and waste move efficiently. Drainage pipes carry the waste out of your home to the city sewer or septic tank, while plumbing air vents supply fresh air to the system each time a toilet flushes or a sink drains. These vents also prevent sewage gases and foul odors from entering your home, as well as help maintain proper atmospheric pressure in the waste pipe system.
If your plumbing vents aren’t working correctly, they may not be allowing air into the drain lines or removing waste gasses. This can cause your drains to slow down, clog often, and even present a health risk if dangerous sewer gases flow into the home. A plumbing service professional can assess the condition of your vents and fix any problems they may have.
The most common way to vent a plumbing system is through a duct running vertically from each fixture to the roof. Another option is to install an air admittance valve (AAV) — these are negative-pressure activated, one-way mechanical valves that eliminate the need for a vent line. These are commonly found in commercial and industrial buildings. If you have two fixtures installed back to back, they can tie into a single vent pipe using a sanitary cross or wet vent. However, this method isn’t allowed by code for toilets and urinals due to the risk of self-siphoning.
Gas Lines
Gas lines bring natural gas from the meter into your house, where it is used for water heaters, furnaces, and gas cooking ranges. These pipelines can be made from a variety of materials, depending on the needs of the system. Pipes that supply a gas line are typically threaded differently than pipes that transport water, with the threads in the opposite direction to ensure that they don’t leak.
In older homes, the gas line will likely be a steel pipe. These will rust and corrode over time, and a leak will occur eventually. This will usually be noticed by a dead patch of grass above the leak, a strong sulfur smell, or a very high gas bill. When these leak, the entire line will usually need to be replaced instead of just repairing it at one point.
Newer homes will often use a type of pipe called CSST, or Corrugated Stainless Steel Tubing. This is a flexible pipe that is much easier to install than black iron pipes and is therefore becoming the preferred option for new home builders.
If you’re considering replacing your existing gas lines, it’s best to call a licensed plumber. A professional can make sure the pipes are installed properly and safely, so you’re not putting your family at risk of carbon monoxide poisoning or fire.