Common Causes Of Clogged Drains & How To Fix Drain Clogs

Whether they carry water or waste, nobody likes the idea of clogged plumbing pipes. If plumbing water encounters a full or partial obstruction, that water will redirect itself and cause reactions that may include anything from backups and flooding to slow drainage and low pressure.

Some issues may cause minor headaches and hassle, while others inflict major damage and expense. Many people want to know how to prevent all types of clogged plumbing situations, or they seek solutions to some type of existing problem. More knowledge about the causes of clogged drains is the best insurance against mishaps, and is always a great preventative measure to take against harmful blockage. What you know can then help to both avoid and identify problems.

It seems like it should be a fairly simple task to find a drain clog and remove it, but fixing clogged pipes can be complex and involved, depending on where the clog is located, what it consists of and what must be done to access and remove it.

Common Causes

Sewer and water drainage systems in a house are configured a little bit like a tree and its branches. There’s a main line that’s usually biggest in diameter, and sublines run off it that are typically a bit smaller in size. While the toilet is probably the most common place where clogs originate, they can start, build and disrupt function in and from any location in the system.

A blockage can build and lodge itself anywhere, but analysis will help narrow down the possibilities. You’ll be able to see what’s happening and what exactly the problem affects. If some part of the water or sewer main is clogged, the issue likely affects the whole household or building. If something is stuck in one of the sublines, whatever is happening will more than likely be isolated to one area or section of the building.

common causes of clogged drains

Here are the most common causes of blocked drains:

tree roots blocking sewer main

Tree roots

Tree roots are widely recognized as the number one cause of blockage and clogs in water and sewer mains. While it’s more common to find tree roots invading the pipes of older homes, the roots can find their way into systems of any age. Some experts say the first sign of tree root invasion into the sewer or water line is a gurgling sound.

As living things, the tree roots seek moisture and are more or less naturally drawn to the water in waste and sanitary sewer pipes, especially if one has a crack or springs some other kind of leak.

If you live in a wooded area, or where there are many trees nearby, it’s important to be on the lookout for any tree root invasion. Some people decide to have a video inspection done every few years, since the cost for the service is dramatically lower than addressing a neglected issue.

18 million to fix clogs

“Flushable” wipes

Flushable wipes can be a detriment to the system. Some cities and other entities responsible for wastewater processing and management have begun to discourage people from using the supposedly flushable wipes. A 2015 report indicated that the City of New York had spent $18 million over five years to deal with all the wipes clogging up the wastewater system.

These moist bathroom wipes, which have grown popular in recent years, have also prompted lawsuits over claims that the products disintegrate after they’re flushed. Allegedly, they don’t break up when flushed and are only called “flushable” due to their ability to physically fit into the pipe.

From small cities to the Federal Trade Commission, wipes and their impact on public systems have become a big deal — so much so that millions of dollars are said to be at stake, and public-education campaigns are active in multiple states and cities. Some water treatment entities have dealt with the problem by buying expensive industrial shredders to process the wipes.

The truth about thick toilet paper, paper towels, facial tissue, light cardboard, and other paper products is that they’re not made to be flushed down the toilet. Home and commercial plumbing systems have the capacity to accept and process water, human waste, and biodegradable toilet paper. That’s it.

Feminine hygiene

Feminine hygiene products and baby diapers pose a danger to plumbing pipes because they do not biodegrade and contain cotton and other fibers that have a tremendous capacity to clog and attract other clogging agents. Neither are biodegradable, and both pose a threat to public and private systems alike.

The sewer treatment contains microorganisms that break down the human waste, but they do not disintegrate anything but that — even when pad wrappers and tampon applicators may claim to be “flushable.”

fat, oil and grease are plumbing pipe enemies

Fat, oil, and grease

Fat, oil, and grease are enemies of plumbing and all its accessories. Another increasingly publicized movement is one to educate consumers about the benefits of keeping oily substances from going down the drain, where they can build up and cause clogs. Employees in a commercial establishment must have specialized training on what does and does not belong in the drain and public system, but people in many private places could benefit from the same knowledge.

We like to think that most of us know better than to pour a pan of bacon grease down the drain or garbage disposal, but we may not think of some of the other things that contain fat, oil, or grease. For example trimmings from a steak or other meat, butter, vegetable oil, chocolate, cream, and more.

It’s easy to think that water just washes everything along, but fats are sticky, binding substances that are prone to causing buildups and eventually clogs. The trash can is a far better place to dispose of fat, oil, or grease. Bacon grease and many other fats and oils can be left to cool and will solidify or congeal for easy cleanup. Another preferred practice is to pour the oil or grease into a disposable container and then toss it in the trash.

hair can accumulate in drains


Hair can accumulate to the point where it creates slow flow or total blockage. We can’t help that hair comes out of our heads naturally, but we can try to protect the drain as much as possible with small screens and good practices, such as sweeping hair out of sinks and cleaning the hairbrushes over the trash can.

When you see hair accumulate on the drain, or maybe hanging from it, use needle-nose pliers or work carefully with long tweezers to pull the hair out regularly, as opposed to letting it sit or wash down the drain. There are also a number of drain screens available that keep hair from going down the drain and make removal easier.

Pipe scale

Pipe scale is a product of nature that interacts with your pipes and can actually build to the point where you have a clog or blockage from the mineral deposits water leaves behind. Scale deposits usually result from dissolved calcium and magnesium and sometimes other metallic elements that are left behind as water flows.

These particles react to temperature as well as constant wet-dry conditions. The scale begins to collect in one spot, which attracts more scale until it grows to an obstructive size. Not only does mineral scale build-up inside pipes, but it can also affect other water-using appliances, such as clothes and dishwashers.


Food bits and chunks should be placed in the garbage — never in the sink, bathtub or laundry drains. It especially should not be flushed down the toilet. None of these drains tolerate much of it, because that isn’t what they were designed to carry. Edibles can be sticky, stringy, sharp or hard, none of which will be good in a water pipe.

While we’ll discuss garbage disposals in greater detail a bit later, know that certain foods are wholly incompatible with even powerful garbage disposal systems. The key to disposals is that they cut the material into tiny pieces that will travel through the drainage pipe without accumulation. Unfortunately, many of the foods we eat aren’t easily shredded.


Disintegration of the pipes can happen, especially with older homes or homes that may have aging concrete, clay or terra cotta pipes. Joints can come apart and drop and soil can erode away, which allows the pipe to sag.

Where it freezes hard in the winter, there exists the possibility that pipes can shift under the continuous pressure and heave of the freeze-thaw process. Even with modern pipes that are usually made of a super-hardened plastic, damage is possible simply from natural soil shifts and seasonal changes.

blockages in drains


Nature sometimes works its way into sewer or water lines, especially where pipes have separated. Leaves, sticks, dirt, rocks and even rodents can create blockages underground that are difficult to detect. Leaves are pervasive and efficient clogging agents, so it’s generally a good practice to keep the yard clear of them and definitely not wash them down the storm sewer drain.

We’ve all seen a tiny weed sneak through the smallest of cracks, and any breach in the plumbing pipes is an opportunity for roots, plants and soil to invade, build and end in blockage.

only human waste and toilet paper should enter system


Objects such as bar soap can break off in chunks and become lodged in the drain, as well as other things that should not end up in there, such as jewelry, children’s toys, condoms, dental floss and food. Again, nothing but water, human waste and degradable toilet paper should go down the system.

The importance of that concept is proven by many articles and entire programs on “how to train” small, learning children and by numerous, humorous bathroom signs that remind adults to only deposit the basics.


Combinations of materials can also team up and stick together to form a big, gooey ball of blockage that leads to strange sounds, slow drains and, eventually, backups. Soaps and detergents can build up, attract other materials and create a clog, especially in septic system drain fields.

The recommendation from laundry experts is to use soaps that do not contain phosphates and which have natural (or no) surfactants, as opposed to ones developed from a petrochemical product. They also advise that those with a septic drain field pace the rate at which they wash clothes, instead of washing them one load after the other, so the system has time to work and doesn’t get overwhelmed.


Slope of the sewer and water pipes must be correct, or it will cause drainage problems and possibly blockage. Gravity drives most of the function of water systems, so it’s crucial that the pipes have the correct slope to flow properly. The standard pitch of any drainage pipe should be at least 1/4 inch per foot, and sometimes more if some other characteristics of the terrain or household demand more slope to properly process the water and waste.


Undersized sewer pipes can be the root cause of blockage and clogs. Unless you’ve been the sole owner of a property since its structures were newly built, it might be difficult or impossible to ascertain its complete plumbing history. Sometimes, people add onto a home or building without compensating for the added plumbing load, and there are plenty of instances where an unlicensed technician or inexperienced do-it-yourselfer miscalculated the system loads.

minimum drain size

The size of sewer drain piping used in a home or other building is determined by the number of water-using units, such as toilets, sinks and bathtubs, that discharge to it. A widely accepted minimum standard for the main drain of a home is four inches in diameter, but many plumbers and consumers will go with one bigger than that based on household needs and usage.


Overload is also possible, even when the sewer main is properly sized — particularly if the household is on a septic system and its waste capacity has grown. The drain field and other workings of a septic system can become overwhelmed and fail to drain, which usually produces bad smells and/or backups.

cat litter belongs in the trashLeaks

Leaks are an enemy of the sewer and main drains, because if water is leaking out underground, the soil will erode as well as become soaked, which will allow the pipe to drop, sag or otherwise change position. The leaking water changes the chemical composition of the soils around it, so the pipe becomes displaced and may even break.

Cat litter

Cat litterbelongs in the trash and not down the toilet or any drain, and the same is true for dog waste in a bag. All kitty litter is made of clay-based material that can actually harden like concrete when it’s been wet and dry enough times. The litter pieces are sharp and can easily catch on other things, which only increases the chances of a clog.

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