I remember my first day on the job as a digger for a septic installation company. Eager to learn everything I could about this vital part of the civilized world, I asked my boss if there was anything specific that I needed to bear in mind. “Yeah,” he said, “Remember that s%!@ always rolls downhill.” This sage advice has proved useful both literally and metaphorically and is an integral part of one of the most essential conveniences of modern living: plumbing.

(Pixabay / Shutterbug75)
The Two Forces in Your Home
Plumbing is broken down into two systems: one supplies fresh water to your home, and the other removes waste. These two systems operate in harmony so well that unless something is wrong, it is rare that you even notice the two parts at work.
The Freshwater System
The freshwater system is what we think of when we turn on the tap. As if by magic, this system delivers clean water to a variety of fixtures, whether it be a toilet, tap, bathtub, or bidet.
It’s not magic that brings the fresh water to your home, though; it’s pressure. Before freshwater can make it to your house, the clean water is pressurized either by large pumps at the public water supply company or via static pressure when it comes from a water tower. This water is then piped to your home where it may or may not be heated, softened, or filtered. When you open the valves on these systems, the pressurized water exits the freshwater system and starts into the next phase of its journey.
The Wastewater System
As my former employer so crassly put it, wastewater is what happens when we spoil clean water, either by contaminating it with human waste or simply sending it down the drain. This water is then handled by the household waste system and eventually either an on-site septic system or the public sewer utility. Either way, the removal of waste is an essential part of modern plumbing.
Gravity is the driving force behind wastewater removal, so when we send water down the drain, the pipes are angled ever so slightly downward so that the water drains properly. When that slope is disrupted, either by shifting earth or a blockage, wastewater can build up in the pipes and cause failure.
In addition to the septic and sewer system, traps and vents help prevent the buildup of harmful gasses in your home. A trap is an area where water accumulates in a P- or S-shaped bend of pipe just below a drain. This water helps “trap” gasses on the opposite side of the pipe from your home. The venting system carries these gasses away from the sewer pipe and upwards towards your roof. As fresh air blows outside around the vent pipe, these gasses are whisked away, preventing smelly buildup in your home. This exchange of air and gas allows water to drain correctly so that it doesn’t need to be siphoned off.
Because the wastewater system is made up of three parts – drain, waste, and venting – it is often referred to as the DWV system, and its pipes are labeled for DWV use.
The Plumbing Basics
Many homeowner today are comfortable handling basic plumbing tasks. Since we live in a world of online tutorials, to-dos such as replacing a wax ring on a toilet or swapping out a faucet are much more accessible than in the past.
If you want to get to know how the plumbing works in your home, start by identifying the basics for each system, such as the freshwater cutoff and the sewer cleanout.
Most homes have a metered connection so that the water utility company can measure how much water is being consumed. Typically, this meter has a cutoff on it as well. For many homes, there is an additional valve located inside or near the home where the homeowner can cut off the water supply for the house. Before attempting any plumbing repairs in your home, be sure to shut off the water—whether it be to the entire freshwater system or simply to the fixture if it is just a localized fix. (Note that most fixtures have an individual control valve that allows you to shut off water to that fixture only.)
In addition, it is typical for homes to have a sewer/septic cleanout located outside the home. This is usually a four or six-inch PVC cap that you can remove so that you can access the wastewater plumbing in the case of a blockage.
Things to Bear in Mind
- Before you start any plumbing repair, it is essential to make sure that you are legally allowed to do it. Some states and municipalities have plumbing codes that require licensing to work on plumbing systems, and violations can be very costly. Confirm with your local plumbing authority to make sure that you are allowed to perform any work on your home plumbing.
- Even if you are an accomplished DIY-er, you should leave some plumbing repairs to the professionals. While changing out a faucet or replacing a toilet wax ring is fairly simple, more in-depth jobs such as adding a bathroom or extending existing plumbing lines may be done better by professionals to ensure that there are no leaks.
- Be sure to use appropriate fixtures outside. Winter temperatures in Utah can get pretty low, so make sure that your outdoor fixtures or piping are rated for outdoor use. A cautionary tale: homeowners often replace hose spigots in the summertime and forget about them. The problem is that temperatures can turn to freezing by late fall or winter. If your new hose bib is not frost-rated, you could encounter disastrous consequences during the most inconvenient time of the year.
- Always know where the next cutoff in the system is because you might accidentally damage the local fixture cutoff valve during your repair. Knowing ahead of time where the next cutoff in the line is can minimize costly damage.
Plumbing is an essential part of our modern life, and because it often works so well, we don’t even think about it until something goes wrong. Taking the time to understand how plumbing works can help you know more about what to do in case of a plumbing emergency, as well as broaden your ability to solve the simple problems that arise from daily use.