Best Flushing Toilets

Toilet Fills Up With Water Then Drains Slowly: Reasons & Fixes

If the toilet draining process becomes slow, it becomes one of the most terrible issues in the house. It may clog the system or decrease the flushing power. As a result, you need multiple flushes to clear the waste.

Possible Causes:

  • Clogged Drain
  • Low Flow Toilet
  • Blocked Vent Pipe
  • Faulty Flapper
  • Blocked Rim Holes
  • Sediment Buildup
  • Weak Fill Valve
  • Chain Length
  • Septic System Issues
  • Sewer Line Issues
  • Improperly Installed or Damaged Pipe

Reasons Why a Toilet Fills Fast But Drains Slowly

If anything happens like this, it means the toilet cistern is problematic. A toilet cistern contains a number of functional tasks that must be completed on time. Some other reasons include the following-

Problematic flushing system

If the toilet flushing system is not working properly, it can be blamed for the slow draining issue. To detect the issue, you have to look inside the toilet tank and flush the toilet with the flushing handle. There is a flush toilet apparatus. It is connected to the handle and opens the flap when you flush the toilet. If you notice that the apparatus is not working, you can be sure that it is one of the reasons for the slow flush of your toilet. So, change the flushing apparatus and repair the toilet cistern.Problematic flushing system

Clogged drain line

If the drain line is clogged, it will not be able to drain sufficient water and garbage through the line. There are several reasons why a drain line becomes clogged. Throwing tissue paper into the toilet, making the toilet dirty with inorganic materials, and throwing plastic, paper, and other things can clog the drain line quickly. Even if you flush the toilet several times, these elements remain in the line. So, you must unclog the line with a plunger and flush it again.Clogged drain line

Problems with the air vent

The air vent with a pipe is necessary for transferring the toilet’s inside and outside air. But the vent should also be clear; otherwise, the toilet flushing system can slow down. The fallen leaves, rodents, or birds can stay inside the air vent and clog it. As a result, your toilet flushing can be problematic.

If you find yourself in this situation, check the air vent immediately and take the initiative to clean it as soon as possible.

The low water level in the toilet tank

Sufficient water in your toilet tank is necessary for power flushing. But if there is a jam inside the pipe of your toilet tank, it will fill up slowly. As a result, there will be a low amount of water, which will make it impossible to flush the toilet forcefully.

The blockage between the tank and bowl

The flushing water comes from the toilet tank through a pipe and goes to the toilet bowl. The flushing water cannot forcefully fill the toilet tank if the pipe becomes clogged. As a result, the toilet drain pipe becomes filled with garbage and is clogged.

Mineral accumulating on jet holes

If your toilet flushing water contains many minerals, they will accumulate in the jet holes when you flush the toilet.

If your toilet’s jet holes are contaminated with minerals, you can remove them by using a mineral remover and a wire hanger. Now, try to remove the accumulated minerals with the remover and the hanger. When the jet hole is entirely cleared, the toilet will be released from the clog again.

These brushes have the perfect ability to clean the minerals from the toilet jet holes. The nylon of the brushes is so thick that they can easily remove the minerals from your toilet’s jet holes.

Related: How often can you use Drano?

How can I take proper care of my toilet?

Every toilet user faces several problems with their toilets. Sometimes they have to pay a lot of money to the plumbers. So you should take some initiative to keep your toilet safe. Now, we are going to discuss them.

i) Do not use bleach tablets

The bleach tablets are corrosive to the rubber seals and pipes. These tablets cause water loss or leakage issues. Finally, the major problem with these tablets is that some cannot dissolve properly in toilet water. As a result, the toilet drainpipe becomes contaminated with the tablets, and toilet clogging happens.

ii) Never pour hot water down a porcelain toilet

Some toilet users apply hot water for a better cleaning experience. It is good for cleaning the toilet because hot water removes germs faster. But it is not perfect for porcelain toilets. Heat can easily crack the porcelain toilet surface. So, you can use a dishwasher detergent to clean the surface efficiently.

iii) Avoid using drain cleaners made of sodium hydrochloride

Drano is a popular drain cleaner. But it is made of sodium hypochlorite, sodium hydrochloride, aluminum, sodium chloride, sodium nitrate, etc. Some of the materials are reliable for corroding toilet pipes.


The slow draining happens in clogging. However, sometimes toilet users notice that the toilet is clear of clogs but still cannot drain quickly. This issue happens because of the obstruction in the drain pipes. In this situation, you must take a plunger and clear the drainpipe.

Sometimes the toilet remains clogged after taking several initiatives. The inexperienced users must call a plumber to solve the issues. Moreover, every user should be aware of how to unclog the toilet and the drainpipes. If the problem still remains, you can call a professional plumber because they are experts in this work.


Question: Why does my toilet fill up with water then drain slowly?
Answer: This is usually due to a clog in the toilet or drain pipe, problems with the venting system, or issues with the flapper in the tank.

Question: What can cause a clog in my toilet?
Answer: A clog can be caused by excessive toilet paper, non-flushable items, or build-up of waste material over time.

Question: How can I fix a clogged toilet?
Answer: Using a plunger is the most common and easiest way to unclog a toilet. You may need a toilet auger or snake if the clog is stubborn.

Question: What is a venting issue in a toilet?
Answer: Venting issues occur when the vents that allow air to escape from your plumbing system get blocked. This can slow the draining process.

Question: How do I fix a blocked vent?
Answer: You’ll need to inspect your roof vents and ensure they’re clear of debris like leaves or bird nests. Call a professional if you can’t do this yourself or the vent is hard to reach.

Question: What is a flapper in a toilet and how can it cause slow draining?
Answer: The flapper is a toilet tank component that controls the water flow into the bowl. If it doesn’t function properly, it can cause the toilet to fill and drain slowly.

Question: How can I fix a faulty flapper?
Answer: If the flapper isn’t sealing correctly, it may need to be replaced. Turn off the water supply, drain the tank, remove the old flapper and install a new one.

Question: How can I prevent my toilet from clogging?
Answer: Regular maintenance, including using a mild drain cleaner periodically, not flushing non-flushable items, and using a moderate amount of toilet paper, can help prevent clogs.

Question: Can a slow-draining toilet lead to other plumbing problems?
Answer: Yes, if left unaddressed, a slow-draining toilet can cause overflow, water damage, and other plumbing problems.

Question: Do I need to replace my toilet if it’s draining slowly?
Answer: Not necessarily. Most issues causing a toilet to drain slowly, like clogs, venting issues, or flapper problems, can be fixed without having to replace the entire toilet.

Question: How often should I clean my toilet vents?
Answer: Generally, you should check your vents at least once a year. If you live in an area with lots of leaves or birds, you might need to check them more often.

Question: What tools do I need to unclog a toilet?
Answer: A plunger is the most basic tool for unclogging a toilet. For stubborn clogs, you might need a toilet auger or snake.

Question: Can I use chemicals to unclog my toilet?
Answer: While chemical drain cleaners can sometimes clear clogs, they can also damage your pipes if used excessively. It’s generally better to use a plunger or toilet snake.

Question: How can I tell if the problem is with the flapper?
Answer: If the toilet seems to be constantly running or if it doesn’t flush correctly, the flapper might be the problem.


Hi, I am Jose S. Franz. Currently, I am working as a professional plumber, and our team offers various plumbing services at an affordable price. After my college education, I completed a vocational certification course in plumbing systems and worked with several construction companies. Since then, I have fixed lots of different toilet models, from older to the latest versions. So I have more than 22 years of experience installing plumbing systems and toilets in both residential and commercial buildings.

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