Reasons Your Toilet Keeps Clogging


A clogged toilet can be incredibly frustrating, not to mention unhygienic. Few things are worse than reaching for the handle to flush, only to watch the water rise dangerously close to the rim as the contents swirl but don’t budge.

If you find yourself plunging on repeat, you’re not alone. Toilets clog for many reasons, and pinpointing the exact cause is key to preventing future problems. Understanding common culprits can also help you unclog your toilet as quickly and effectively as possible when needed.

Below we’ll explore the most likely reasons your toilet keeps clogging, from everyday items flushed down to serious plumbing problems. We’ll also provide tips to remedy clogs and prevent them from occurring in the first place. Read on to learn why your toilet may keep getting stopped up, and what you can do for smoother flushing ahead.

Reasons Your Toilet Keeps Clogging

There are several common causes of recurring toilet clogs:

1. You’re flushing inappropriate items

One of the most prevalent reasons toilets clog is inappropriate items being flushed down them. Many people use their toilets as small trash cans, flushing things that should be disposed of in the garbage.

Some commonly flushed items that can lead to clogs include:

  • Paper towels – Paper towels are thicker and stronger than toilet paper. They don’t break down easily in water.
  • Facial tissues – Like paper towels, facial tissues are designed to be sturdy and won’t break down in water.
  • Cotton balls – Cotton balls can quickly accumulate in drains and trap other debris.
  • Dental floss – Dental floss is meant to stand up to the friction of teeth; it won’t break down in your toilet.
  • Cotton swabs – The cotton tips may come off the sticks, but the sturdy stems can clog drains.
  • Condoms – Condoms are very resilient and will clog drains and pipes.
  • Cat litter – Kitty litter turns into a heavy, clay-like substance when wet.
  • Sanitary pads and tampons – These absorbent products won’t disintegrate in water.
  • Diapers – Diapers are specifically designed to absorb liquid and will swell to clog pipes.
  • Cigarette butts – Cigarette filters will accumulate in pipes.
  • Paper and plastic – Any paper or plastic inserted into the toilet may cause a clog.

Flushing anything other than human waste and toilet paper will up your clog chances. Be sure to toss out the trash instead of flushing it. Educating children and houseguests can also help prevent inappropriate flushing.

2. Blockages in the drain pipes

Your toilet relies on a series of drain pipes to remove waste from the bowl into the main sewer line. If any of these pipes are obstructed, draining will be slowed or stopped completely.

Some common causes of drain blockages include:

  • Build-up – Years of drain use can create thick build-up inside pipes. This build-up narrows the diameter and impedes flow.
  • Roots – Tree roots can invade pipes through cracks or joints, blocking flow.
  • Damage – Cracked, broken, or misaligned pipes prevent waste from flowing freely.
  • Clogs – Accumulated wipes, grease, and other debris plug pipes.
  • Rust – Corrosion and rust eats away and thickens pipe walls, narrowing the path.

Blocked drain pipes under the toilet can make flushing sluggish or impossible. You may be able to remedy this by using a plumber’s snake to remove the obstruction. In some cases, drain repairs may be required.

3. Vent stack issues

For a toilet to drain properly, air needs to enter the drain system so water can displace it. This enables waste to essentially get “sucked” down the pipes.

Vent stacks allow air to enter the system. If vent stacks are blocked or improperly installed, air can’t enter and waste can’t drain. This results in gurgling noises, slow draining, and recurrent clogs.

Vent stack problems include:

  • Clogs – Debris blocking the top opening of the vent stack.
  • Blockage – Damage or improper installation blocking air flow in the vent stack.
  • Height issues – Vent stack that does not rise high enough to proper vent air.

Problems with your home’s vent stacks will require professional repair. A drain technician can assess your system and make needed corrections.

4. Low water levels in the tank

Your toilet relies on a siphon action triggered by tank water to create flushing power. If water levels are too low, siphoning won’t initiate properly when flushed. The contents may drain sluggishly or not at all.

Some reasons for decreased tank water include:

  • Leak – Small leak at the supply line, tank fittings, or flapper allowing water to escape.
  • Crack – Hairline crack in tank or bowl leaking water.
  • Valve issues – Fill valve not opening enough or closing prematurely.
  • Warped tank – Tank warped and no longer holding correct volume of water.

Take a look inside your toilet tank and check for issues. Adjusting the fill valve may fix minor problems. Larger leaks, cracks, and tank warping will require toilet replacement.

5. Weak flush

Even with adequate water levels, your toilet bowl shape and siphon may be inefficient at creating a strong flush. Weak flushes don’t create enough “scouring” water flow to clear waste in the bowl and drain lines.

Common causes of weak flushes include:

  • Low water level – As mentioned, low tank water diminishes flushing power.
  • Small trapway – Older toilets often have very narrow drain pipes that don’t allow vigorous flow.
  • Warped toilet bowl – A warped or misaligned bowl can break the siphoning action.
  • Plumbing leaks – Leaks downstream of the toilet can reduce flush strength.

You may be able to improve your toilet’s flush by adjusting the tank water level or replacing flapper and fill valves. In many cases, however, the only remedy is to replace the entire toilet. Newer models are specifically designed for more effective siphoning and clearing.

6. A fouled flush valve

The flapper or flush valve at the bottom of your toilet tank plays a key role in initiating a flush. When you press the handle, this valve is lifted and the tank water rushes into the bowl.

Over time, flush valves can become weighted down with mineral deposits from water. They may warp or develop cracks. A fouled flush valve can’t seal properly between flushes, resulting in leaks. It may not lift fully when flushed either, allowing debris to remain stuck in the bowl. A faulty flush valve is a common cause of double flushes and ghost flushes too.

Inspect your flush valve and replace if necessary. Scrape and clean off any large mineral deposits. Modern flappers are very inexpensive and easy to swap out.

Preventing Recurring Clogs

While occasional clogs happen in all toilets, frequent backups indicate an underlying problem needs to be addressed. Here are some ways to prevent repeated clogs:

  • Avoid flushing anything besides waste and toilet paper – This simple habit prevents many objects from obstructing your drains.
  • Use a toilet-safe cleaner regularly – Non-abrasive cleaners designed for toilets help break down waste and debris before flushing.
  • Check for leaks – Slow leaks allow mineral buildup and require more frequent plunging. Fix any leaks promptly.
  • Inspect your vent stack – Ensure your vent stack is free of debris and rising properly from your roofline.
  • Upgrade old or faulty equipment – Switching to a high efficiency toilet with a wider trapway and more effective flush can prevent future clogs.
  • Call a plumber for persistent problems – If DIY efforts aren’t working, call in a professional to inspect for blockages or faulty plumbing that needs repair.

Unclogging a Repeatedly Clogged Toilet

When faced with a chronically clogged toilet, here are some tips for clearing the obstruction:

Try a plunger

A simple plunger is incredibly effective at dislodging blockages. Follow proper plunging steps:

  • Prepare the plunger – Ensure the bell is tightly attached to the handle. Wet the rim to form an improved seal.
  • Position the plunger – For sink clogs, cover the drain tightly with the plunger. For toilets, position it several inches over the drain to cover water in the bowl.
  • Plunge vigorously – Work the plunger up and down rapidly 10-20 times to dislodge the clog. Repeat until water starts draining.
  • Flush again – Once water is moving, flush the toilet again while keeping the plunger positioned to clear any remaining debris.

Use a closet auger

If plunging fails, a closet auger (or “toilet snake”) can break up stubborn obstructions:

  • Insert the auger – Feed the auger down into the toilet drain past the trap. Don’t force it.
  • Crank the handle – Turning the handle will advance the spiral end through the curves of the drain and break up the clog.
  • Retract the auger – Once water starts draining, slowly extract the auger while cranking to clear any remaining debris.
  • Flush – Flush the toilet again once fully retracted to ensure the drain is fully cleared.

Try a drain snake

A longer drain snake fed through the toilet access port and into the drain line can dislodge clogs further down the pipes. Use a screwdriver to remove the toilet base access panel. Insert the drain snake into the drain and turn the handle while pushing forward. Retract the snake once the drain is cleared.

Use a closet auger

For severe blockages, an extra-strength chemical cleaner can help dissolve the clog. Caution should be used, as these cleaners contain concentrated acids or alkalis.

  • Wear gloves – Corrosive cleaners can cause skin burns. Eye protection is also a good idea.
  • Read instructions – Follow product directions closely to avoid accidents or damage.
  • Apply the cleaner – Pour the cleaner into the bowl according to package directions. Most cleaners require allowing time to work before flushing.
  • Flush carefully – Flush slowly at first to allow the acidic water to drain. Repeat treatment if needed.

Call a plumber

For frequent or unresolved clogs, calling a professional plumber is advised. They have the high-powered equipment needed to clear difficult blockages in drain lines that are inaccessible to consumers. A plumber can also diagnose and repair any underlying issues, like pipe damage or vent issues. Though pricier, professional drain cleaning services can save you from chronic clog headaches.

When to Call a Plumber

While many toilet clogs can be cleared with some elbow grease, several situations warrant calling in a professional:

  • Inability to clear clog after multiple attempts using a plunger, auger, and drain snake.
  • Foul sewage odors emanating from toilet.
  • Leakage coming from base of toilet.
  • Very slow draining not improved with plunging.
  • Water draining out of the overflow pipe on the toilet exterior.
  • Toilet completely backed up and unable to flush at all.
  • Drain gurgles loudly after flushing.
  • Suspected issue with vent stack or main sewer line.
  • Chronic clogs continue occurring after repairs and upgrades.

A plumber has the tools and know-how to fully clear drains and diagnose issues that may require reconstruction. For severe clogs or ones that keep returning, a professional assessment is recommended.

FAQs about Clogged Toilet Troubleshooting

What is the most common cause of a clogged toilet?

Flushing inappropriate items down the toilet is the most prevalent cause of clogs. Paper products, personal hygiene items, and trash should always go in the garbage can rather than the toilet.

Why does my toilet clog after flushing just once?

A toilet that clogs after one flush often has severe buildup of mineral deposits and waste in the drainage pipes that limit flow. Calling a plumber to clear the blockage is recommended.

Why does my toilet clog for no apparent reason?

Unexpected clogs that occur out of the blue are often caused by a sudden shift in the blockage within pipes. Something previously stuck in the drain finally moves enough to fully obstruct water flow.

Why does my toilet bubble when it clogs?

Gurgling bubbles are caused by air trapped in the drain system. A venting issue, blocked vent stack, or siphon problem can cause this. A plumber should diagnose and repair the underlying issue.

How can I unclog my toilet without a plunger?

For mild clogs without a plunger on hand, a couple cups of hot water poured from waist height into the bowl can help clear the blockage. Add a couple squirts of liquid soap to lubricate the contents. You can also wrap the end of a coat hanger into a small hook to fish out debris. For severe clogs, however, a plunger or snake is required.

Why does my toilet keep clogging after I use it a few times?

If a recently-emptied toilet re-clogs after only a few flushes, there is likely an obstruction caught in the trap curve of the toilet drain. A plumber’s snake should be able to break up and extract the debris.


Dealing with a frequently clogged toilet can try anyone’s patience. While it may seem like a lost cause, understanding the common reasons toilets clog can set you on the path to smoother flushing.

In most cases, simple adjustments to equipment, plumbing, and household habits provide a long-term solution. For more severe or recurring issues, professional drain cleaning and repairs may be needed. But by knowing what typically causes toilets to clog up, you can take the right steps to prevent problems before they arise.

With some awareness and preventative care, a chronically clogged toilet doesn’t have to be accepted as part of life. Take back your bathroom by addressing the root causes so you can flush with confidence once again!