shower water down the drain

Where Does Shower Water Go?

The plumbing system in a home is located under the ground and in the walls. Therefore, unless you’ve installed a plumbing system before, or work in a similar trade you won’t be aware of where shower water goes. In this article, I will explain where shower water goes once it goes down the drain in your shower.

As a general rule, shower water goes into the municipal sewage lines that are connected to a home, or into a septic tank. It depends on the plumbing setup a home has. A septic tank disperses water into the soil but needs to be drained once it gets full but a truck that comes and sucks it out. 

The way a septic tank works is a little bit complex, but not difficult to understand once you know how they work. 

There are also more details about how the shower drain is connected to the municipal sewage lines, and whether the water from a shower mixes with the wastewater from a toilet, and kitchen sink. So, below, I will cover this in detail so you will know exactly where shower water goes after it goes down the drain.

Does All Waste Water From a Home Go to the Same Place

Home drain and sewer system vector infographic

There are multiple drains in a home, and a few places where wastewater is produced such as the toilet, and washing machine. Here’s a summary of whether all the wastewater in a home goes to the same place.

In general, all wastewater from a home flows into the same place, either the municipal sewage lines that run underneath the nearest street or into a septic tank installed somewhere on the property. All wastewater connects to a single pipe that goes to either place.

As you may know, the municipal sewers (government wastewater sewers) all flow to a wastewater treatment plant. Here the water is filtered and various processes are done to it such as filtering it and using chemicals to break down bacteria.

But, if your property is fitted with a septic tank, it needs to get emptied periodically once it gets full. You will know if you have a septic tank because you’ll know it needs to be emptied when it gets full. A septic tank disperses some of the wastewater underground on your property. 

There are networks of pipes that run onto a bed of gravel, or similar material beneath the ground. Where it filters into the ground, microorganisms break it down, and it gets mixed into the soil. 

A septic tank only disperses water and not the solids in wastewater. Solids are left in a septic tank and settle to the bottom of the tank. Over a long period of time, the solids build up to a point where it needs to be emptied.

Here’s a video that shows how septic tank emptying works:

This includes the sinks in the kitchen, the toilet, the basins in your bathroom, the washing machine, the dishwasher, and the shower.

There are also what are called greywater sewage systems. These are a way of conserving water so that there is less demand placed on the city or town’s wastewater systems.

For example, if you brush your teeth, or wait for a tap to heat up, the water that goes down the drain is virtually perfectly clean, and could easily be reused. 

Other water such as that from a washing machine or shower is only slightly dirty and can be reused. So, it is a little bit of a waste for all of this water to go to the wastewater treatment plant.

Do Showers and Toilets Share the Same Drain

There are multiple drains located throughout a house. Once used water or wastewater goes down them it goes out of sight. So, here’s whether the shower and the toilet go down the same drain, and connect together in the plumbing underneath the house.

In general, a shower and a toilet do not share the same drain, but they connect to a single pipe, and the wastewater goes to the same place. A shower drain and a toilet have separate pipes that connect together. This pipe either goes to the government sewer lines or to a septic tank.

While showers in a home and toilets don’t have the same drain, they do ultimately connect up into one pipe. This pipe is where all of the wastewater made in a home goes to. Such as from the kitchen sink, the dishwasher, and the washing machine.

Does Sink Water Mix With the Toilet Waste Water

There is water that goes down the drain from the sink in a vanity unit. A toilet has a much wider pipe, and also deals with large amounts of waste and toilet paper, which is very different from the mostly water that goes down the sink in a vanity unit. 

As a general rule, sink water and toilet water mix in the plumbing and go through a single pipe to the municipal sewer lines, or to a septic tank. The sink water goes through the pipe at the base of the sink, and when a toilet is flushed the wastewater goes down a separate pipe.

Both of these pipes connect to each other and go down a single pipe. At the base of both pipes is what is called a p-trap fitting. If this wasn’t there the pipe would be open from the end of the pipe to the drain in the bottom of a sink. 

Therefore, any bad odors from the bacteria in the pipe would come up through the sink. This is less of an issue with a toilet because a toilet has water that sits at the bottom. However, a sink does not. A p-trap is a ‘u’ shaped pipe and water sits at the bottom of it permanently which creates a seal between the sink and the rest of the pipe.

One of the reasons a bathroom can have bad odors is if the p-trap is dry due to a leak or a blockage in the air vents. I explained this in more detail in this article about why a shower drain stinks.

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