How Does Plumbing Work in an Apartment Building?


If you live in an apartment, then you share a plumbing system with other inhabitants of the building. Depending on how big the building is and how many floors it has, it will likely have multiple dwelling plumbing systems.

If the building is especially tall then it will be difficult for the water pressure to be enough for the whole building and for all its residents.

So the multi-story plumbing system will be able to create water pressure such that the bathroom and kitchen in each apartment get a good flow of water. The following are some basics of how plumbing works in an apartment:

Multi-Story vs Multiple Dwelling

Apartment buildings are typically divided between multi-story dwellings or multiple dwellings. The former, as has already been explained, is for taller buildings that require greater water pressure, so each unit in the building gets running water.

Multiple dwellings, on the other hand, will also have separate apartment units. However, these buildings may not be as tall and may not require the same kind of water pressure.

The idea of the multi-story plumbing system is that it branches out further so that more plumbing fixtures can get water. It is not too different from a single unit plumbing fixture, except that the system is replicated for multiple apartments.

Are Apartment Drains Connected?

A multi-story plumbing system will typically have vertical stacks, horizontal pipes and branch lines. The vertical stacks for multiple apartments may be connected.

Vertical stacks are what serve as your plumbing vents. These stacks will ensure that there is enough air pressure maintained in the plumbing system so that no harmful sewage gases are trapped anywhere.

There are a few different types of vertical stacks. Leaders are vertical stacks that are used for carrying rainwater collecting on the roof down to the drainage system below.

Soil stacks are what will be connected to the water closet and urinal, while waste stacks will be connected to plumbing fixtures that do not deal with human waste.

Other than that, the pipes that you see in your apartment and immediately surrounding your unit are likely just for your own apartment. But it is often possible that 2-3 apartments may share pipes or just a particular section of the pipes.

At times, the waste line from multiple apartments may run into a common line for all the apartments. In that case, a clog in one of your neighbors’ pipes may cause your plumbing fixtures to backflow.

However, this depends entirely on how old the building is and how the sanitation system has been constructed. Typically, newer buildings will have separate pipes for separate units which will go down directly into the waste line.

Apartment Plumbing Issues

When you live in an apartment building, there may be some common plumbing issues you may have to deal with. The following are some of these issues:

Network of Fixtures

For starters, often you may not know what pipe may affect which apartment. There is a network of pipes and vents, often they may even be common for multiple apartments.

So if you move one or accidentally damage one, it can be difficult to know which apartment has been affected. There is a complex network of pipes, vertical stacks and branch lines that must be navigated so you do not accidentally snag your neighbor’s water supply.


Creating the right kind of pressure is another problem. Each apartment unit needs to get good water pressure so there is running water coming through the pipes. In order to achieve this, some apartment complexes may install roof tanks and a motor that is able to draw water from the ground floor storage tanks.

The roof tanks then offer the appropriate height required for gravity to do its work and allow water to flow into each unit.

You may also need to add a booster pump to pull water from the storage tanks into your home. Each apartment may have its own booster pumps which will, in turn, exacerbate the existing water pressure.

Hydro-pneumatic storage tanks are another option where water from the storage tank is pulled into the hydro-pneumatic storage tank. From there, air pressure will help push the water to different units in the building.

Frozen Pipes

Frozen plumbing pipes during the winters mean that the water supply to all apartments will be affected. If the lines are connected and if the common line does not have insulation, even if you have installed insulation for your drainage pipes, it will create a clog even in your pipe, causing you to be without water.

Even worse, the pipes may burst under pressure and cause important areas in the apartment building to get flooded. The separate apartment units will need to coordinate together to ensure the pipes are insulated. It may also be a building mandate that the heat has to be on in every apartment so that the pipes do not freeze during extreme weather.

Clogged Drains and Toilets

If you share a common line with other apartments, then a clogged drain could cause water to backflow in your plumbing systems as well. This is one of the most common plumbing problems in an apartment building as when one apartment is affected, several adjacent units may also get impacted.

It is, therefore, important to impose strict sanitation rules for the buildings. An older building may enforce rules like no flushing toilet paper. They may even be strict about putting grease down the kitchen drain. A shower drain clogged by hair in an upstairs unit can cause water to backflow in several units below as well.

Final Thoughts

Living in an apartment building to a large extent means committing to a symbiotic living arrangement. What one does in their own apartment unit may have repercussions on somebody living in the unit downstairs.

It is important to maintain a building code that ensures everyone has working pipes and vents, ensuring there is a good flow of running water. The good thing is you can always contact the supervisor if there is a problem in your apartment instead of taking on the headache of fixing a plumbing issue by yourself.

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