Your home’s plumbing system is obviously one of its most important components as it drains sewage and wastewater out and away from the building. The plumbing stack is what allows this to work properly and is the most vital part of the system. Since most people aren’t familiar with plumbing stacks, let’s take a look at exactly what they are and how they work.

Understanding the Parts of a Plumbing Stack

The plumbing stack is a vertical pipe that runs from the roof down through the house. It continues down through the foundation where it meets your main sewer line that channels waste into the municipal sewer main out in the street.

A plumbing stack is separated into three parts. The pipe that extends through the roof is known as the vent stack. Below this is the drain stack, which is where all of the various branches coming from your toilets, sinks and other fixtures drain into. The lowest part of the stack that extends down through the foundation is the soil stack, and this is where the stack ties into your main sewer line.

What Does the Drain Stack Do?

The role of the drain stack is simple. Every plumbing fixture in your home has a drain pipe and each of these pipes ties into the central drain stack. This allows the wastewater from your sinks, toilets, washing machine and dishwasher to drain into your main sewer line.

What Does the Vent Stack Do?

The vent stack serves an extremely important role by allowing air to enter the drain stack. Whenever you flush the toilet or put water down the drain, it essentially creates a vacuum inside the pipe. If there is no air inside the pipe, then the wastewater would get stuck in the pipe as the vacuum prevents it from draining.

Every time you flush a toilet or use your sink, the pressure from the water moving through the drain system draws air in through the vent stack. This air helps to force the water down through the pipes to ensure everything drains correctly.

The vent stack also serves another important purpose by venting sewer gases out of the plumbing system. Whenever your drain system is empty, all of the sewer gases inside it rise up through the drain stack and out of the building through the vent pipe. This works in conjunction with the P-traps in all of your drains to prevent you from smelling nasty sewer odors rising up through your sinks and drains.

Each branch connects to the plumbing stack using a sanitary tee. There is a slight curve in the bottom part of the tee that directs water down into the stack. Gravity causes the wastewater to flow downwards, and any sewer gases inside the branch rise up from the tee and are vented out through the roof.

Since the vent stack sticks out above your roof, it can often become clogged with leaves and other debris. When this happens, it blocks the pipe and prevents air from entering the drain system. If the vent stack is completely clogged, your drain system won’t work. Instead of traveling down the drain pipe into the drain stack and out of your sewer line, the wastewater gets stuck inside the pipes. This eventually causes a sewage backup since the vacuum prevents it from draining.

What Is the Plumbing Stack Made Of?

Unless you have an older home and haven’t had your plumbing system redone, your plumbing stack will most likely be made of ABS or PVC plastic just like all of your drain pipes. In older homes, the plumbing stack may be made of cast iron, galvanized steel or even lead pipe.

If your plumbing stack is made of anything other than PVC or ABS, we highly recommend that you have it replaced sooner rather than later. The reason is that these metal pipes are highly susceptible to rusting and corrosion, which means that they will eventually start to leak. Should this happen, you could face a huge issue with water damage, mold growth and waste leaking out inside your home.

Identifying the Signs That Your Plumbing Stack Needs Repaired or Replaced

As with the rest of your drain system, the main issue that can affect the plumbing stack is clogging. If the vent pipe or any other part of the plumbing stack is blocked or even partially obstructed, it will create issues every time you flush the toilet or put water down a drain.

These problems usually result from flushing or washing things down the drain that you shouldn’t, such as paper towels, flushable wipes, cotton pads, feminine hygiene products and condoms. It can also happen if you put oil, grease or fat down the drain as these can harden and create a sticky coating inside your pipe that will easily trap other solids and eventually completely clog the pipe.

A full blockage will eventually result in sewage backing up inside your drains or even overflowing out of your toilets. Luckily, there are typically other quite noticeable signs that can indicate when your pipe is beginning to get clogged or the plumbing stack is otherwise not working properly.

One of the most obvious signs is if all of the drains in your home are slower than usual. This can indicate that the vent stack isn’t letting enough air in or that there is a clog in the plumbing stack or your main sewer line. You will often also hear bubbling or gurgling noises coming from your pipes whenever you use the sink or flush the toilet.

Plumbing stack issues can also cause the sewer gases inside the system to back up inside your home instead of exiting through the vent stack. Sewage odors inside the home can also indicate that your vent stack is leaking.

If not enough air can get into the stack, it changes the air pressure inside the system. Each of your drains has a P-trap that prevents sewer gases from coming up through the drain. This works by holding a small amount of water inside the bend at the bottom of the pipe, which creates a seal that prevents the gases from escaping out of the pipe. The water remains inside the bend due to the pressure on the other side of the pipe. When this pressure changes, the water can get sucked out of the trap and gases can freely flow out of the drain.

Visible wet spots or mold on your interior walls are a sign of a more serious issue. In this case, it indicates that either your water lines or plumbing stack are leaking. If you notice these issues, it is vital that you immediately call a professional plumber to inspect your system and find and repair the leak.

Reliable Plumbing Services in Denver

If you’re experiencing issues with slow drains, sewage smells, backups or leaks, you can count on Summit Heating, A/C, Plumbing & Electrical to repair the problem and get your plumbing system working properly again. We specialize in drain cleaning, leak detection and pipe repair, and our experienced plumbers have the knowledge to quickly diagnose any plumbing issue. If the problem is related to your main sewer line and not the plumbing stack, we also specialize in sewer line repairs and replacement. To schedule an appointment to have your plumbing inspected, give us a call today.

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