Usually, when a drain clogs, you can either plunge it or use drain cleaners -- and it then starts flowing freely again. But what if the drain seems to get clogged repeatedly? If your drain seems to be spending more time clogged than not, there may be a bigger issue brewing. Here are some of the most common causes of repeated drain clogs.

Scum Buildup Inside the Drain

Sometimes, drains may accumulate a thick layer of scum at certain points. This scum grabs onto larger debris like hair or food particles, leading to a clog. When you plunge or clean the drain, you dislodge the larger components of the clog and get water flowing again, but the scum remains -- allowing the drain to reclog the moment something sticks to the scum again.

So, what is the scum inside drains comprised of? In some cases, it may be soap scum, especially if you use a lot of all-natural or clay-based soaps, which tend to leave more scum than shower washes and conventional detergents. In other cases, the scum may be comprised mainly of grease. This is often true in kitchens where people rinse grease and fat down the drain. In recent years, however, grease clogs have been appearing in bathroom drains as people are using coconut oil to clean their mouths and moisturize their skin.

If you suspect a layer of scum may be to blame for your repeated drain clogs, try rinsing the drain with a big pan of boiling water. Pour some vinegar down the drain periodically to get rid of soap scum, and stop putting any form of oil or fat down the drain.

Plugged Sewer Vents

Homeowners usually assume the drain pipe is to blame for the slow movement of water down the drain. However, sometimes the problem is in the vent stack that allows air to escape from your sewer lines. The vent stack lets air escape from the pipes so that suction does not keep drain contents in place. If leaves, a birds' nest, or some other debris ends up in the vent stack, air can't escape the sewer pipes, so water won't go down, either.

If you are confident climbing on your roof, take a look down your sewer vents. Shine a flashlight in there, and see if you spot any debris accumulation. If there is debris in the vent, call in a professional to clear it out. (If the debris is right near the top of the stack, you may be able to just reach in and grab it.)

A Clog in the Main Line

Another possibility is that the clog is located further down in the drain line -- perhaps in the sewer main that empties into the public sewer. With enough pressure, the clog may dislodge partially, allowing water to pass through. But then more toilet paper and debris gets stuck, and the flow slows down. 

Unfortunately, clogged main sewer lines are difficult to deal with. This is not an issue you can handle yourself. A professional would have to dig up the line, either remove the clogging material or replace the whole pipe, and then rebury the pipe underground. This can cost a few thousand dollars. A drain cleaning company can send a camera down into your main pipe to see if this is a problem before they dig it up.

If you are sick of dealing with repeated clogs, take action. There's probably something bigger going on, and until you address that bigger problem, your drains will likely keep backing up and clogging. Contact a plumber in your area, such as Complete Plumbing, to learn more.