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Toilet Won’t Flush or Has a Weak Flush? Causes & 8 Solutions

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Nobody wants to use the toilet and a weak flush makes them flush two times or even more. It’s even worse when they have to pour water down the toilet in a gallon container just to empty the toilet bowl.

If it always takes you two or more flushes to clean up the bowl instead of accomplishing this in a single flush, it may be time to fix the problem. Most likely, a low water pressure issue in your toilet.

Low water pressure can affect the toilet flush making it slow and less powerful in carrying waste down the hole at the base of the toilet.

Without a doubt, a toilet with a weak flush can be frustrating, embarrassing, and even messy. Especially in the guest bathroom. After all, you wouldn’t want to give our guests a hard time when they use the powder room, right?

Scroll below to understand and solve this problem.

What Causes Low Water Pressure In The Toilet & How To Fix It

If you’ve realized the signs of a weak flushing toilet, it’s most likely that the water pressure in your toilet has dropped. The following could be possible reasons and solutions for them:

Cause 1. There’s Not Enough Water in the Tank

The first thing you should take a look at when assessing the possible cause of low water pressure in your toilet is the water level inside the tank.

First, remove the lid of your toilet tank to look inside. New toilet models will have a mark on the side of the tank to indicate where the water level should be for optimal flushing power.

Usually, it is below the edge of the overflow tube in the tank to keep the tank water from siphoning into the overflow tube as this will continually run the toilet and wastewater.

When there is not enough water in the tank, your toilet will not be able to deliver enough water per flush.

Solution: Adjust the Float

If the water level in the tank is lower than it should be, consider adjusting the float assembly that will either be a cup float or a ball float.

If the toilet has a ball float, adjust the ball float height by turning a screw at the top of the fill valve with the water still on and the tank full. This adjusts the tension in the arm and raises the float to in turn raise the water level.

Now, flush the toilet and monitor the water pressure. Generally, with more water in the tank, the force it exerts on the bowl should improve.

Cause 2: A Clog in the S-Trap

Toilets have an S-trap that sits between the toilet bowl and the drain line.

It functions to stop foul gasses and water from flowing back into the bowl as well as filter debris and other objects that might stop wastewater from flowing through your sewage pipes.

Because of this, clogs tend to occur in this area of the fixture. The trap can clog when a significant mass of excess waste, toilet paper, and other non-flushable items like sanitary pads and diapers are flushed and get stuck in the toilet trap.

Such a clog causes a slow and ineffective flush unless removed.

Solution: Remove Clogs Using a Plunger or Auger

If a clog seems to be causing the reduction of pressure in your toilet, try plunging the toilet to clear the blockage. A flanged plunger will force water through the trap and move the clog.

A toilet auger is another way to unclog the toilet if plunging doesn’t work. Insert the auger into the toilet drain and move it until you hit the resistance. Now rotate the auger to dislodge the clogged material, then hold on to pull what’s left out of the drain.

If you still can’t get the clog to clear on your own, it’s time to call a plumber for drain cleaning services.


After using a plunger to unclog your toilet, it may fall t a low water level, and in some cases, not flush. This should not worry because it is a result of pushing water out of the S-trap with the plunger. The next time you flush, it should be normal again.

Cause 3: A Blocked Toilet Vent

Toilets are connected to a vent, usually through the roof that allows fresh air to enter your home’s plumbing system, increasing the flush pressure.

But if the vent is clogged with any debris like leaves, then the toilet loses flushing pressure. Poor pressure causes the toilet to clog more frequently, and eventually, this becomes a recurring issue.

Other household problems brought on by a blocked toilet vent include gurgling sounds coming from the toilet, slow drainage throughout the house, and sewage odors indoors.


To unclog the toilet vent, climb up to the point of the roof where the vent is, remove the vent cap and using the nozzle spray on your garden hose, send water down the vent to clear the blockages.

You can also use a toilet auger to remove the blockages. Afterward, try flushing the toilet to confirm if the blockage is cleared. If the water pressure is still low, get help from a plumber.

Cause 4: Clogged Rim/Siphon Jets

Also known as flush holes, or siphon jets, these rim jets are small holes located underneath the inside of the rim of the toilet bowl to push water from the tank down the sides of the toilet bowl so all wastewater flushes down the drain.

With every flush, minerals accumulate around these jet holes, and over time, the buildup causes pressure to get less and less powerful. To provide more water pressure, it is, therefore, necessary to clear up these mineral deposits.

Check for clogged flush holes if your tank is full of water and your drain is free and clear.


To fix this problem, clear the jet hole buildup by using a hot vinegar solution. Simply heat up white vinegar to up to 120 Degrees and pour it down the overflow pipe in the toilet tank using a funnel.

Let the vinegar sit to an hour or two. Generally, it will be sitting on top of the rim jets. After the vinegar loosens the mineral deposits, use an Allen wrench to clear our the buildup.

Cause 5: A Running Toilet from a Worn-Out Flapper

The toilet flapper is a rubber seal that covers the opening between the toilet tank and the toilet bowl by closing off the flush valve to keep water in the tank.

It also opens up the valve when the handle lever is pressed allowing water to flow into the bowl.

Over time, the flapper can become warped, dirty, or broken, and no longer provides a full seal. Other times, it just won’t close so your toilet continues to run. This significantly reduces the flush pressure.


Start by flushing your toilet repeatedly to completely empty the tank before examining the flapper. The flapper can then be detached from the tank’s base and pulled upward for a closer look.

If the flapper has any stains, discoloration, damage, or build-up, see if you can clean it so that it will once again function. However, if the flapper is damaged or cannot be cleaned, it can be easily replaced.

NOTE: The best way to fix an old, worn-out flapper is to replace it.

Cause 6: A Loose Handle & Chain

The flush chain is connected to the flush lever( toilet handle) and the flapper.

If the chain is too short it will constantly pull up on the flapper allowing water to trickle into the bowl and if too long, it might stop the flapper from closing properly and sealing the water in the tank.

A loose handle and chain cannot initiate a proper flush, requiring more flushes to clear waste. Therefore, solve this issue first by checking the length of the chain by jiggling the flush lever and watching the chain between the lever and the flapper.


You can easily replace a loose chain with a smaller one that is the appropriate length.

Cause 7: Water Level in the Bowl Is Too Low

Your toilet won’t flush effectively if there is not enough water in the bowl.

If the water level in the tank is normal but that in the bowl is low, there could be a problem with the fill valve device located in the tank.

Remove the tank lid and flush it a few times to determine whether your fill valve is causing the water level in the bowl to be too low. It has a leak if water is spraying out of the fill valve’s top.

In such a scenario, the fill valve has a leak therefore, the tube that fills the toilet bowl loses water pressure as the fill valve splits and shoots water.


To fix this, simply upgrade your fill valve to a better model.

Cause 8: An Old Toilet & Old Pipework

The toilet itself may occasionally be the cause of the low water pressure – an old-generation toilet to be precise. These toilets, especially those from the mid-to-late-1990s, have limited force when it comes to moving waste down the drain.

More so, the old pipework in such houses can also cause clogging in your toilets. Such pipework that is aged is also prone to collapsing hence a source for clogs.


If living in an old home from the 90s with old toilets, it might be time to consider an upgrade. Switch to modern toilets that have low-flow designs that prioritize efficiency and water use.

Additionally, you will need to get a plumber to assess the condition of the pipes. Be prepared to repair or upgrade your pipes if necessary.

You May Also Like: Low-Flow Toilets: Are They Worth It?


How Do You Fix Low Water Pressure In A Toilet? (10 Solutions)

How can I quickly fix my slow-flushing toilet? Above are the main causes of an inadequate flush and solutions that can help you out the next time you have a weak flushing toilet.

NOTE: Unless, you have technical experience, we always recommend the services of a professional plumber.

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