A tuft of long fallen hair in the toilet bowl.

Can You Flush Hair Down the Toilet

A toilet will still flush when you put various different things down it. But, over time clogs are common when things that should be flushed are flushed down the toilet. Today, I will explain if hair can be flushed down a toilet.

As a general rule, you should not flush hair down the toilet. The pipe in the plumbing for a toilet is wider than the drains for a vanity unit, and most showers. So, a clog from hair is less common. But, hair can very commonly cause a clog in plumbing.

In general, long hair is much worse to flush down a toilet than short hair. The surfaces of the pipe are completely smooth so it’s unlikely a piece of hair to stick to the sides and build up. But, there are various parts along the sewage system of a toilet where hair can get caught and cause a clog.

Where Hair Will Cause a Clog if Flushed Down a Toilet

The number one reason not to flush hair down the toilet is that it can cause a clog. As you may know when you flush the toilet the waste goes out through the wastewater lines which go into the city sewage system. Here’s a really good video that shows how the plumbing in a house works:

When hair is flushed down the toilet, goes down the shower drain, or goes down a kitchen sink it goes into the pipe that goes to the wastewater. This typically isn’t an issue for the wastewater itself because it gets treated at a water treatment facility that removes it.

I wanted to know how common it is for a blockage in plumbing to be caused by hair. So, I did a survey of plumbers. Here’s a table that shows the results:

How many times has hair caused a blockage in the plumbingPercentage of votes
Less than 10 times9.7%
Over 10 times32.2%
More than 20 times12.9%
More than 30 times45.2%

As you can see, from the responses hair causing a blockage in the plumbing is very common. About 90% of plumbers say that hair has been the cause of a blockage more than 10 times. 

One plumber reported that it’s most common in the bathroom sewage lines. Whereas, in the kitchen, it virtually never happens. This makes sense because it would be very rare for someone to put hair down the kitchen sink. Whereas, in the shower, bathtub, vanity, and toilet it would be far more common.

How a Hair Clog Develops

One of the main reasons a hair clog develops in the sewage is because it takes a very long time for hair to break down. As normal waste such as poop and toilet paper interacts with water it becomes softer. Whereas, hair remains as it is. Some estimates are that hair takes 2 years to decompose (source). 

There are 2 main ways that hair can cause a clog in the sewage if it’s flushed down the toilet:

  • It can snag on the inside of the pipe and then catch small amounts of debris that pass over it, eventually building up into a clog
  • Hair will get tangled in itself. As more and more hair is flushed down the toilet it will create a mesh that traps waste as it travels through the pipe

If you’re lucky hair will travel through the pipe without catching on anything. But, there are joins in the plumbing where a piece of hair can get snagged. Which will eventually snag other pieces of hair. 

In older pipes, the inside can also get a bit rough. And a small piece of PVC pipe sticking out can catch a piece of hair that eventually builds up into a clog.

Older style pipes made of cast iron aren’t used in plumbing anymore. But, can still be around, especially in older homes. 

The reason they aren’t used is that over some time the inside develops rust, which eventually clogs the pipe. Hair running through a pipe that is even a little bit rusty will easily snag and cause a blockage.

What’s the Best Way To Dispose of Hair

Various parts of the body grow hair, and trimming, waxing, or plucking hair is very common. You can have a lot of removed hair or only a small amount. Here’s the best way to dispose of hair.

In general, throwing hair in the garbage is the best way to dispose of hair. Hair takes around 2 years to fully decompose. It can technically be buried in the garden or put into the compost. But, because it takes so long to decompose it’s generally impractical to do so.

The reason is compost is typically ready within 6 months to a year. Sometimes, a lot sooner. Therefore, when you go to use it, the hair won’t have decomposed yet. Burying it in the garden somewhere where it won’t be disturbed is a very good idea. But, it’s typically much easier to throw it in the garbage.

What Happens if You Flush Hair Down the Toilet

A bathroom typically has a mirror, which makes it a very convenient place to trim hair. A toilet can also handle many different kinds of waste such as soft food scraps. But, here’s a rundown of what happens if you flush hair down the toilet.

Overall, flushing hair down the toilet once or a few times won’t do anything. But, plumbers don’t recommend flushing hair down the toilet. Hair very commonly causes blockages in sewage. It’s best not to risk causing a blockage by flushing hair down the toilet.

The risk that it does cause a blockage is far less if you have new plumbing. But, old plumbing and especially cast iron plumbing can cause hair to get stuck, and cause a blockage much more easily. 

For example, old cast iron pipes typically have rust, and rough edges on the interior, which very easily snags hair. Also, older pipes can have imperfections on the interior which can also easily snag hair.

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