Slow Draining Toilet? Here is How to Fix It Quickly

Why is My Toilet Draining Slowly?

Toilets depend on gravity in order to produce a suction/siphon effect which pushes waste from the bowl up and down the trap, and out into the drainpipe. For that to happen, both the toilet trap and drainpipe have to be free of obstructions.

A slow draining toilet is almost always caused by a partial clog in the toilet trap or drainpipe. The clog creates a restriction which prevents waste from flowing out as fast as it should, and may even develop into a full clog if not fixed.

Slow draining toilets can sometimes be caused by a clogged vent stack. A clogged vent stuck will however affect other fixtures in the house and you will also notice the bathtub or sink draining slowly as well.

To fix a slow drain bathtub, pour half a cup of dish soap in the bowl followed by by a gallon of hot water. If that does not fix the problem use plunger to dislodge the clog or a toilet auger to pull it out. In case of a blocked vent stack climb to the roof of the house and unclog it.

Let us now look at all the things that cause a slow draining toilet in more detail.

1. Clogged Toilet Trap


A toilet trap is the U-shaped bend at the bottom of the toilet which looks like an inverted P, and that is why it is also known as a P-trap. Every fixture in your house has P-trap for 2 reasons:

  • It holds a steady amount of water in the bowl which acts as a barrier preventing sewer gases from coming up into the bathroom.
  • It traps potential clogs, preventing them from clogging the drainpipe further below where it would be way harder to unclog

The toilet trap unlike other drain traps has one more importance. This is what allows a toilet to flush. The siphon effect is generated here.

It has a short leg and a long leg. Once you flush the toilet, water fills the bowl all of a sudden which also fills the toilet trap’s short leg. When that happens, wastewater flows and fills the long leg as well.

The weight of water in the long leg will pull the water in the short leg and the bowl as well until all wastewater has been siphoned out. This is how a basic siphon works.

If there is clog in the toilet trap, you will notice that the siphon is not as strong as it used to or should be and you may also need to flush the toilet twice.

2. Clogged Drainpipe

All the fixtures in your house have separate drainpipes. All this separate drainpipes are further down connected and drain to the main house drainpipe which in return drains to the city’s sewer lines or septic tank.

If the toilet drainpipe is partially clogged, you will have a slow draining toilet. You will notice that when you flush the toilet the bowl fills with water which then drains slowly.

If you have several toilets in the house, check if the problem is with only one toilet or all of them. Also check if other fixtures in the house like sinks and tubs/showers are draining slow as well.

Sometimes slow draining fixtures are caused by tree roots in the sewer lines. If not killed while still small, tree roots in sewer lines will force you to replace the sewer pipes, which is not cheap.

3. Clogged Vent Stack

A vent stack is the vertical pipe running from your house’s drainpipe through the roof of the house. It provides a way for sewer gases to flow out of the drainpipe and also allow free circulation of air in the drainpipe.

If the vent stack is clogged, pressure will build up inside the drainpipes causing a slow draining toilet. Other signs of a clogged vent stack are:

Unless the problem is with all of your other fixtures, a clogged vent stack cannot affect one toilet only.

How to Fix a Slow Draining Toilet

Fixing a slow draining toilet is quite easy and in most cases you will not even need to call in a plumber. There are several ways you can use to fix a slow draining toilet, depending on what is clogging it.

Here are some of the ways to unclog a slow draining toilet starting off with the easiest to the hardest:

1. Use Hot Water and Dish Soap

This is the best method to unclog a slow draining toilet without a plunger or snake. Here is how to proceed:

  • Use a sponge to soak up the water at the bottom of the toilet bowl. Please remember to have your gloves on.
  • Pour about half a cup of dish soap in the toilet bowl.
  • Dash to the kitchen and boil about 1 gallon of water.
  • Dump the water in the bowl and give it time to work out its magic.
  • After about 30 minutes flush the toilet and check if its draining rate has improved.
  • You might need to do this a few times to completely fix the problem

If your toilet trap or drainpipe was clogged by toilet paper or bar of soap, the hot water will help break the clog into smaller pieces and in the process unclog the toilet improving its draining rate.

2. Use a Toilet Plunger


A toilet plunger is an effective tool for dislodging clogs from the toilet trap or drainpipe. It works by creating a pressure differential between the top and bottom of the clog, where the pressure at the top is more than the one below it.

This forces the clog to move further down the drainpipe and in the process restore your toilets draining rate.

Remember to select the right plunger for your toilet. There are 2 types of plungers. Flat-bottomed plungers and bell-shaped plunger. The right toilet plunger is the bell-shaped one.

It seals perfectly round the toilet bowl opening allowing you to send maximum pressure down the drainpipe. This is how to fix a slow draining toilet using a toilet plunger:

  • Add some water in the bowl. In order to plunge effectively, the bottom of the plunger needs to be fully immersed in water.
  • Position the plunger gently on the toilet bowl’s opening and ensure it seals all around the opening. Some people opt to apply Vaseline around the rim of the plunger to help it seal better.
  • Start plunging. The first plunge needs to be gentle to help the plunger form a tight seal on the toilet bowl opening.  After the first plunge start plunging aggressively for a few minutes.
  • Lift off the plunger and flush the toilet. Has the draining rate improved? If not plunge some more

In case you would like to explore more ways of unclogging a toilet without a plunger, check out this post.

3. Use a Toilet Auger


A toilet auger, also known as a plumber’s snake is a device used to unclog toilets by shredding the clogs into smaller pieces or even pulling them out. It has a helical and hooked head, flexible cable and cranking handle.

The main problem with using a toilet auger is that if you are not careful it can badly scratch your toilet bowl. Fortunately, it comes with a protective guide that helps you introduce and pull the head without coming into contact with the surface of the bowl.

Here is how to unblock a slow draining toilet using a toilet auger:

  • Pull the cable inside the tube such that the head of the auger is at the bowl guard.
  • Slow introduce the auger inside the bowl and position it on the bowl’s opening.
  • Start pushing the cable down through the toilet trap until you encounter resistance.
  • Crank the handle clockwise until you go through the restriction. If it feels too hard crank the handle in the opposite direction and start again.
  • When you finally go through the restriction or if it feels too hard pull the cable inside the tube and lift off the bowl guide and tube without making contact with the inside of the bowl.
  • If you manage to pull out the clog, flush the toilet and check if it is draining properly again. If not insert it again and try once more.

For more information on how to unclog a toilet with a plunger check out this post.

4. Unclog the Vent Stack

If the toilet and other fixtures in your house indicate that you have a clogged vent, then unclogging it is quite easy. Here is how to unclog a vent stack:

  • Climb to the roof of your house with a garden house in hand.
  • Check if there are blockages at the top of the vent that you can easily remove with your hand.
  • Stick the end of the garden hose inside the vent and use it to probe it. You might just dislodge the clog.
  • Have someone turn on the water to the garden hose. The weight of the water is usually enough to unclog it.
  • If the water doesn’t do it, upgrade to a plumber snake.
  • Push the snake in the vent until your encounter a restriction. Crack the handle until your hook the clog. Pull it out and push the snake back again to check if there are more clogs.
  • Flush the toilet and check if the draining rate has increased.

Slow Flushing Toilet?

Often people confuse slow flushing toilet with slow draining toilets. Slow/weak flushing toilets are cause by several factors one of them being clogged siphon jet and rim holes.

This is usually a problem for people living in areas with hard water. Minerals and specially calcium block the rim holes and/or siphon jet meaning that water from the toilet tank enters the bowl slowly resulting in a weak flush.

Cleaning the toilet siphon jet and rim holes will without a doubt solve the problem. More information about how to unclog siphon and rim jets in this post.

Another cause of a slow flushing toilet could be as a result of loose lift chain. A lift chain is the chain which connects the toilet handle and the toilet flapper. When it is too loose, it will not fully lift the flapper during flushing and hence the water will drain from the tank to the bowl slowly.

I have written a detailed post on how to fix a slow flushing toilet. Read it here.