Toilet Fills Up Then Drains Slowly (Causes and Solutions) 

According to a survey conducted by Kohler Co, there are over 28 million clogged American toilets every month. That included my toilet at some point I might add, and maybe yours too. The study also divulged that over half of recorded respondents said their fixtures were more than 10 years old. What this means is, if you experience a toilet drainage issue, you are not alone.

While there are a number of causes for a slow drain, oftentimes the reasons are not so far-fetched and often are caused by us. One of the common causes of a slow drain is a clogged drain and this happens when you put an undissolvable substance into your toilet. While the toilet doesn’t come with a manual, in your next maintenance appointment, ask about what shouldn’t go down the toilet. 

Now, Although clogged toilets are a common phenomenon, it’s not a situation anyone desires. So, if you are experiencing a clogged toilet, you need to know the causes and solutions. Knowing the causes will help you prevent possible pitfalls and a solution will always be handy. In this guide, you’ll find the common causes of a slow-draining toilet and how to fix it. 

Let’s take a look.

Why is my toilet draining slowly? 6 common reasons 

Below are six common reasons responsible for slow-draining toilets; 

Clogs caused by non-flushable Items 

A clogged toilet from non-flushable materials is common in family homes. Kids may put non-flushable items down the drain. You may also flush some difficult-to-drain materials unknowingly. 

Paper materials, sanitary, and grease may look drainage-friendly, but they are not. Your toilet’s inability to break down these items will cause a blockage that makes your toilet drain slowly. So, avoid flushing fats and oil, paper napkins, cotton buds, diapers, and other sanitary down the toilet. Instead, dispose of them in the bin and keep all non-flushable items from your kids. 

Maintaining a clog-free toilet can be as simple as keeping away non-flushable items from your toilet. But this is only one of the reasons your toilet may clog. Keep reading to learn more. 

Low water level in the toilet tank 

Is your toilet draining slowly because of a low water level in its tank? Remove your toilet tank lid to check. If the water in the toilet’s tank isn’t enough, your toilet won’t have the ability to flush quickly. So, you’ll notice a slow drain rather than the quick flush you are used to. 

If the tank is full, it can generate enough pressure for the water to flow seamlessly. But if the tank is almost empty, some contents may flush down the drain, but most of it would be left in your toilet. 

Your toilet tank water level can be low for many reasons. First, it could be because your fill tube is damaged or broken. If this is the case, water stops flowing before filling the tank, causing your toilet water tank to be low. 

The problem may also be from your float height, drain line, or toilet bowl. If your toilet bowl breaks or drain-line blocks, contact a professional for help. If you notice an issue with your toilet float, adjust the water float to fill the toilet tank before the valve shuts. This way, there will be enough water in your tank, creating adequate pressure to let the water in your toilet bowl drain properly.

Clog in rim jet or toilet port

Rim jets are openings where water travels from the toilet tank to the toilet flow during a flush. The rim jets are structured to create a circular flow to flush properly. Toilet ports are tiny holes inside the toilet bowl that transfer water from the tank to the bowl. 

Minerals, debris, and grease often block these holes, affecting how your toilet drains water. Your toilet’s rim jets also get clogged with lime, minerals, and other tiny substances over time. If this happens, your toilet will begin to flush slowly. Bacteria also builds up on your jet rim, clogging it further.

If you suspect this is why your toilet is clogged, place a small mirror on your jet rim. If you notice a black or orange spot, it is filled with bacteria. If it’s a scaly color you see, the jet rim is blocked with mineral deposits. The solution to both problems is a thorough cleaning process.

Damage to the flushing mechanism 

The toilet mechanism is connected to the toilet’s flap handle. Ideally, the chain that links the flap to the mechanism should be tight and not slack. If it’s slack, it’s malfunctioning, and it will affect the flush process (even causing the toilet bowl not to fill correctly). So try to make it taut if it’s slack. But you may need to install a new one if it’s completely damaged. 

Flushing mechanism 

A blockage between the toilet bowl and tank 

Your tank may be draining slowly because of a blockage between your toilet bowl and tank. If minerals or other substances build up in the tank, the water will transfer into the tank slowly, resulting in slow drainage. 

How do you know if there’s a blockage between the toilet bowl and the tank? Check to see if water is coming from under the rim. If it’s not, then the flow is probably affected. To fix this, drain the water in the tank. Afterward, press down the hole or use white vinegar to dissolve the substances causing a blockage. 

Damage sewage venting 

A sewage vent is an open pipe on your roof. It enables air to pass through the plumbing pipes for water flow.  It also controls air pressure so that gases and stenches from the toilet can escape through the roof. So, your sewage pipe must be in good condition to maintain your home’s air quality. 

Unfortunately, different substances can clog the pipe, from dust to dirt, leaves, etc. As a result, it affects the air quality and slows down your drainage system. Since checking the sewage vent for clogging signs can be daunting, look for other signs. For example, if you notice prolonged stench in the house, it could be because your sewage vent is damaged. You can contact a professional to confirm your suspicion and fix it. 

How To Fix A Slow Draining Toilet (4 solutions) 

After you’ve identified the major cause of your slow toilet drain, the next step is to fix it so your toilet’s drainage system can return to its best condition. Here are four possible solutions to help fix this issue. 

Unclog toilet with DIY remedies 

You can use various DIY methods to unblock your toilet drainage system. A plunger is one of the easiest ways to unclog your toilet to get rid of the substances obstructing a quick drain. To use a plunger, insert it into the toilet and make your first plunge. Expect water to splash backward at you when you do this. Afterward, push the plunger back and forth to clear any buildup in the system. 

You can also use baking soda and vinegar to unblock your toilet’s drain. First, add a cup of baking soda to your toilet, and wait for two minutes. Afterward, pour two cups of vinegar into the toilet. Vinegar and baking soda cause some bubbles, so pour the vinegar into the toilet slowly to prevent the bubbles from overflowing. 

Hot water and dish soap is another way to dissolve substances buildup and unclog your toilet. To do this, heat water and pour soap dish soap into the toilet while you are at it. Don’t let the water boil. Instead, pour it into the toilet when it’s hot. Then, wait some minutes and flush the toilet with water to unclog the drainage system.  

A toilet auger can also unblock your toilet and allow the water to flush out quickly. Like other drain snakes, a toilet auger has a metal cable penetrating the drainage to unclog substance buildup. You can try these methods to eliminate dirt and substances that block your toilet drainage. For convenience, start with the materials available in your home.

Clean toilet ports and rim jets 

Regular cleaning and maintenance of your toilet ports and jet rim can prevent slow water drainage. You can also clean your jet rim and toilet ports if you notice stains and bacteria to stop the toilet from draining slowly.  

Add water and bleach to the tube and flush the toilet if you find bacteria in your jet rim. Wait for a while after this. Then, clean the jet rim with a cleaner. Afterward, add more bleach to the tube, leave for a few minutes, and flush the toilet. 

If the jet rim is blocked by mineral scale, warm one and a half cups of white vinegar,  put it in the tube for about thirty minutes, and flush. Next, clean the jet holes to eliminate dirt and mineral deposits.

Coat hangers and muriatic acid are two major ways to clean toilet ports. For the coat hanger method, twist and bend at a 45- degree angle. Next, put a tiny mirror on the coat hanger bed. Afterward, check the toilet rim to locate toilet ports with mineral deposits. Then, plug in an inch of wire to clean the ports carefully. 

For the Muriatic acid method, mix muriatic water with water and put a funnel in the overflow valve. Pour some of the mixtures into it. Leave it for about thirty minutes. Afterward, pour the rest of the solution into the funnel in the overflow valve. Wait for another thirty minutes and flush the toilet until all substances are gone. 

Cleaning your jet rim and toilet ports is often a quick fix to a slow-draining toilet. So, if your toilet isn’t draining as fast as it used to, check the jet rim and toilet ports for mineral and bacteria growth.

Unblock sewer line vent on roof 

You may need to contact an expert to unclog the vent on your roof for convenience. However, follow these steps carefully if you decide to do it independently. 

  • The first thing is to confirm if the drainage issue is coming from the vent. You must ask yourself some questions to do this. Do you notice a rotten egg smell in your tubs and sinks? Does your entire home stink? If it does, follow the next steps. 
  • Climb the roof, and ask your aid to flush the toilet. Then, place your hand over the vent. The vent is likely clogged if you don’t feel any suction. 
  • Unclog the vent with a plumber’s snake.
  • Afterward, ask your aid to flush the toilet again. If you feel a suction this time, your vent is unblocked and in proper condition. 

You can clean the vent from inside your home to prevent it from clogging in the future. To do this, put a PVC directly in the vent’s position, whether it’s your kitchen or bathroom. Then, insert a plumbing snake inside the PVC and run downwards or upwards till you locate and clean the clog.

When in doubt, contact a plumber 

Although this step-by-step guide will help you fix most issues with a slow-flushing toilet, you don’t have to do it alone. Reach out to a professional for help if you think you can’t fix them independently. 

Also, contact a plumber if the problem persists after you’ve tried the solutions in this guide. An expert will help you: 

  • Remove a damaged fill tube by draining the toilet tank,  locating the toilet fill valve, and detaching the faulty toilet valve. 
  • Replace the new valve by removing it, installing a new valve, and carefully tightening the valve nut. 
  • Replace a broken toilet bowl by detaching the toilet tank, removing the toilet bowl, and installing a new one. 
  • Change the sewage vent on your roof by removing the nails keeping the vent in place, removing the existing vent, and placing a new vent in its place. 

You can use a plumber’s help to fix your toilet drainage problems, whether it’s the toilet jet rim, port, vent, or tank. So, don’t hesitate to contact a professional if you aren’t confident in your repair skills and if your toilet water keeps draining slowly. On average, the hourly wage for a Plumber in the U.S. is $29 as of October 27, 2022, but the range typically falls between $25 and $33.


Many people experience a slow-draining toilet regularly. However, quickly identifying and fixing the causes will prevent further damage and help your toilet drain correctly.

This guide highlights and discusses the common causes of a slow toilet-flushing process and provides solutions. You can try tips in this article to fix a slow-draining toilet. However, we recommend contacting a plumber if you consider any of the methods discussed challenging. A plumber will assist you in areas you find difficult to handle.

Finally, avoid draining non-flushable materials, and inspect and clean various toilet parts to prevent recurring issues.

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