The Basics of Your Home Plumbing System

Your home plumbing system is a vital part of your living environment. It supplies clean water, removes waste, and protects your home from the dangers of floods and sewer back-ups.

Your home’s plumbing is made of two different systems: the supply system and the drainage system. The supply and drainage systems interact but remain independent. Visit Website to learn more.


Whether taking a shower, flushing a toilet, or cooking with water, our homes depend on plumbing. And while a fully functioning home plumbing system is complex, it’s actually pretty simple to understand how your house’s pipes bring freshwater in and drain wastewater out. Understanding a few basics can help you troubleshoot issues until your plumber arrives.

The main pipe that brings incoming freshwater into your home is called the water supply line. It’s usually located in front of your home and runs underground from a city water main. It passes through a meter that tracks the amount of water you use and then into your home. This piping is often made of plastic, iron or copper, and is under pressure to deliver high-quality water for your showers, faucets and toilets.

Once the freshwater gets into your home, it’s distributed via another set of pipes, the distribution system. This is a series of smaller tubes that connect all your household fixtures and appliances to the larger water supply pipes. Water flows through these small tubes at a rate that can handle your family’s peak water demand. Each fixture also has its own individual shutoff valve, so you can shut off the flow of water to any specific area of your home as needed.

As for the waste water, it’s pumped out of your house via the drain-waste-vent (DWV) system. The DWV system is made up of a network of drain lines, sewer lines, and vents that carry sewage out of your home and into the municipal sewer system or your private septic tank. All the pipes in the DWV system are angled downward to facilitate this flow and prevent wastewater from backing up into your home.

Another component of the DWV system is the trap. Every drain, except the kitchen sink, has a trap that’s filled with standing water to stop sewer gases from entering your home. If the trap becomes dry, it must be refilled with water to keep sewer odors from wafting through your home. By law, all drains must have a trap to protect your health and safety.

The plumbing system in your house has many parts that all work together. The basic functions are bringing water in, moving wastewater out and regulating pressure. The pipes are all over your home, hidden behind walls and under floors, but they are all connected to one main line that brings potable (clean) water into your home. This water comes from the municipal supply, your well, or a combination of both. It enters your house through a curb valve at the street or, if you have city water, through the main line that runs alongside the sidewalk. A water meter and main shut-off valve are usually located near this water meter.

Your water supply system then routes this incoming water to your faucets, showers, tubs, toilets and appliances like the washing machine. It also supplies filtered drinking water. The water is heated by your water heater when needed for hot water. Your water supply system may also include a pressure regulator to keep the water flowing properly and a backflow preventer to protect against contaminants in the water.

Other parts of your home’s plumbing are the drain-waste-vent system and the natural gas plumbing for your furnace, water heater and clothes dryer. This is not an in-depth overview of these systems, but it will give you a good idea of what goes on “behind the scenes” to make your life at home comfortable and convenient.

Understanding your plumbing system will help you minimize panic and expensive repair bills when something goes wrong. It will also enable you to make informed choices about fixtures and other components so your home’s plumbing system works the way you need it to. This will save you money, improve the quality of your lifestyle and help to preserve your home’s structural integrity and value. It will also reduce the amount of waste sent to landfills because you’ll be conserving and reusing water rather than sending it to the dump. The most important thing to remember is that plumbing follows the simple laws of gravity and water under pressure seeking its own level. If you understand these basics, the rest is easy.

Behind your walls and under your floors is a network of wastewater drainage pipes that carry away your sink, tub and toilet waste. These drain lines must be properly vented to keep gasses and foul odors from getting back into your home. This venting is accomplished with a pipe known as a plumbing vent, or sometimes referred to as a plumbing air vent. This vent is a vertical pipe that connects the drain line to your roof. The vent pipe removes gases and odors from the drain pipes and allows fresh air to replace them, allowing water to flow freely.

Every household drain must be able to vent, and each drain must have its own separate vent. Otherwise, gases will build up in the pipes and prevent water from flowing. The telltale sign of a blocked vent is a rotten, sulfurous smell coming from your drains. If your plumbing doesn’t drain well, or you suspect a vent problem, call a plumber to investigate.

Most plumbing codes require that your vent be one size larger than the drain it’s connected to, and that it have a cleanout to allow for cleaning of the vent and the trap. The cleanout should also be close enough to the main vent that you can use a auger to clear any debris that might block it. The main vent is often an underground horizontal pipe that leads to either the municipal sewer system or a septic tank. In new homes, the main line might be PVC; in older houses, it might be clay or another porous material. Tree roots may work their way into the main line, causing wastewater to back up into your house, which is not good for your health or your pipes.

Your plumbing vent pipe runs from the fixture to the roof, and might be tied into a vent stack or to a revent alternative or loop vent. If you’re doing a remodel, it’s important to have an experienced plumber help plan and install the correct venting for your home. Seek professional advice on how to best tie your venting system, and have a local plumbing inspector approve your plans before construction begins.

One of the most important parts of any home plumbing system is its drain-waste-vent (DWV) pipe network. This part of the plumbing system removes gray water and sewage from sinks, tubs, showers, toilets, and other appliances, carrying them to your septic tank or the city sewer line. The DWV system also vents those wastes to the outside so that they can’t build up inside your house and cause problems.

Every drain has a P-shaped trap that holds water and blocks odors, and this trap seal is protected by a piece of flexible plastic called a p-trap extender. However, if pressure fluctuations within the drainage pipes cause that p-trap to lose its water seal, then that trapped odorous gas can make its way up into the house. That’s why every drain needs a properly functioning plumbing vent to break the suction effect and keep the trapped gases from entering your living spaces.

A faulty plumbing vent can also lead to dangerous and expensive drainage problems. It’s a common cause of “slow-to-drain” sinks, bathtubs, and toilets, as well as loud gurgling noises coming from your drains and pipes. If you notice these signs, then you should call a plumber immediately to clear your vents and restore your plumbing.

Most people don’t give much thought to their home’s plumbing vents, but they play a crucial role in keeping your plumbing system working correctly. Understanding how they work can help you understand why they sometimes become clogged or damaged and what to do about it.

Plumbing vents are long, flexible pipes that run from each of your drains up through the roof. If you look up on your roof, you’ll be able to see these pipes poking out of the roof, and they are usually capped with metal or other protective material.

A faulty plumbing vent causes negative pressure in the drainage system, which prevents water from flowing down the drains and can even lead to a build-up of sewage inside your pipes. The vents allow air to enter the drainage pipes to overcome this negative pressure, so water can flow out of your drains again.