Low Water Level in Toilet Bowl- Not Filling After Flush: Causes & Fixes!

The toilet bowl holds about three cups of water at the bottom, right before the toilet trap. The water acts as a seal keeping away foul smells from the drainpipe from getting into your house. In some cases, you will see that the water level has receded and it’s lower than the level you’re used to seeing.

Low water level in the bowl especially after flushing is a common toilet problem that indicates an issue with the fill valve or fill tube, a crack in the bowl, a clog (partial or full) in the trap or rim jets, or a blockage in the vent pipes.

All you need is to inspect the right places and quickly fix the problem before it blows out of hand. The following are details on the possible causes and solutions.

Faulty Fill Valve-Poorly Positioned/Damaged

The fill valve usually controls the volume of water flowing into the tank once you flush the toilet. When in the wrong position, the tank will have a low water supply, therefore, your bowl will not fill.

fill valve
Float cup fill valve


A quick fix for this issue is to adjust the position to raise the level of water in the tank. Adjusting the fill valve will depend on the type of fill valve in your toilet tank. The following is how to increase the amount of water on the most common types of fill valves.

Float-Cup Fill Valve- Some come with a plastic screw mechanism that allows you to slide the float up to raise the water level while others come with a metal spring clip that you pinch to raise the float up on the rod to raise the level of the water.

Plunger/Piston and Brass Diaphragm Ballcocks -Gently bend the float rod up to increase the water fill level in the tank

Plastic diaphragm ballcocks-These come with an adjustment screw on the top that adjusts the height of the float rod and ball. To raise the level of water use a screwdriver to turn the screw counterclockwise.

Internal Float Fill Valve-Twist the top head of the fill valve counterclockwise to unlock it, then move the entire head up to raise the water level in the tank.

Floatless or Pressure-Activated Fill Valve- Empty the tank to access the valve. On top of the valve, there is an adjustment screw that you can turn clockwise to raise the water

Further Reading: How to Adjust Toilet Fill Valve to Lower/Increase Water in the Tank

Other issues to fill valves include;

Stuck Metal diaphragm Fill Valves

These fill valves are usually made of cast brass and tend to rust over time. When this happens, the metal arm tends to get stuck, leaving the floating ball in the same position. The solution is to clean up the rust and adjust the fill valve. Replace the cast brass fill valves with plastic (PVC) ones that are durable and moisture(rust)-resistant

Worn-out/Damaged fill valve

Just like any other item, over time fill valves will wear out resulting in leaks and other issues. Simply replace the old one with a new one.

A Cracked Toilet Bowl

In some cases, there could be a crack in your toilet that gives off water slowly leaving the bowl empty or with reduced water levels. The bowl can crack anywhere, at the base, the back, or the sides.

The cracks can be hard to find especially if they are tiny or in hidden and inaccessible parts of the bowl.

The only evidence you will have to ascertain that there’s a leak in your bowl is if there’s water around your toilet unit.

This shows that water is leaving the bowl and dripping to the floor.

Cracks in toilet bowl


Because the bowl bears a lot of weight from various users and the bowl itself, replacing the cracked bowl is the best long-term solution. This might be costly especially if you have a one-piece toilet.

If the crack is small and above the water level, you can use a waterproof plumber’s putty to seal it. A good recommendation is Harvey’s Stainless Plumber’s Putty

Plumber's Putty for toilet bowl cracks
Harvey’s Putty

Even though the sealant will do the job, it’s only temporary, meaning you may have to fix the toilet again in the future. Replacing the bowl is a better option. Call in a plumber to have them fit it in properly, especially at the base. This should fix your problem if you were also experiencing bowl leaks.

Damaged Fill Tube

The refill or fill tube is a small flexible plastic hose, usually black in color, that links to the overflow tube within the tank.

Its function is to instruct control the amount that flows through the overflow tube into the bowl after every flush.

Toilet Overflow and refill tube
Overflow and refill tubes

Without a properly functioning refill tube, the toilet bowl will either have too little/no water, or overflow with too much water.

After some time, the tube can unclip from the overflow tube or wear out leading to the toilet tank filling with water and discontinuing water flow before the bowl fills adequately.


Open the tank to visually inspect the refill tube for any damages and if it is properly clipped. If it’s worn out and cannot be fixed, replace it immediately and if it’s in good condition but not connected to the overflow tube, position or clip properly.

Partial Clog in the Toilet Trap

Whenever there’s a clog, there’s a siphoning effect in the trap of the toilet. Waste from the drainpipe keeps sipping on the water as it tries to unclog itself. The water may get sipped enough to lower the usual water level in the bowl.

To confirm if this is what is causing the low bowl water level, you should flush the toilet and observe what happens. The water overflows a bit up to the rim of the toilet, after which it sips slowly until it passes the normal water level on the bowl. Sometimes it can even drain the bowl completely.

A blockage can be anything from as small biodegradable waste to tampons, foreign objects, and more. Check the trap of the toilet as it may be siphoning water from the bowl. If you find the blockage, there are several things you can do;

  • Establish what type of clog is in the trap
  • For biodegradable waste, fill a five-gallon bucket with water and pour it quickly into the bowl. You can also vinegar, baking soda or bleach. Plunging is also an option. This will release any blockages from the trap way. Check for any water backing up.
  • Use an auger or snake for tougher clogs.
  • For large pieces of waste such as diapers, stuck in the drain, wear rubber gloves and use your hands to locate and remove them.
  • Here are more good unclogging techniques.

Dirty/Clogged Toilet Rim/Siphon Jets

Siphon/rim jets are openings underneath the bowl rim that let in water from the tank into the bowl when you flush.

If these openings have some dirt in them or are blocked, the amount of water that will flow into the bowl won’t be enough. At the same time, the pressure at which the water will flow will be quite low. All these mean a weak flush which results in a low bowl water level.


Inspect the source of the dirt/blockage, ensure the tank is clean. Use a vinegar solution and a scrub brush to clean the jets;

Further Reading: How to Clean Toilet Siphon/Rim Jets for a Stronger Flush

Blocked Sewer Vent Pipe

In addition to removing gas and odors from your home, the vent pipe system also regulates air pressure and plays a role in how water moves through the pipes.

Sometimes, if there’s a blockage, the vent pipe will try to seek air from other outlets in the house. You will hear gurgling noises as water is siphoned along with the air.

In other cases, the moment you flush, water exits the trap way very fast, down the pipes leaving the bowl empty, followed by loud gurgling sounds and sometimes some foul smells. This means the air seal has been broken and there is no more suction. Water may return to the bowl, but just a little.

If you stay somewhere that’s filled with lots of trees, this is a very likely problem for you as leaves, small branches, debris, birds’ nest among other things are some of the most popular causes for vent blockages.

Apart from the blockages, the pipes might also be worn out and might be leaking, therefore reducing water pressure.

Generally, a problem within your vent system always affects the water pressure, drainage, and flushing power.


Use a ladder to get on the roof and clean and clear the plumbing vents to allow free flow of air in the venting system which in turn balances the pressure.

If you experience this issue of blocked vents often, consider getting a cover for your vents, or just a grid to prevent the leaves and branches from getting into the vent, blocking the pipes again and again.

If the blockage is beyond your reach, call a plumber immediately. Professional plumbers will inspect the vent pipe on your roof and use specialized equipment to check for any blockage.

Failure of Water to Flow from the Supply Valve

This will happen in case your pipes are old and they leak. It also happens in case the valve that controls the flow of water into the tank is shut.

The valve is probably placed behind the toilet tank and is adjacent to the wall. In case the valve shuts itself or someone mistakenly shuts it off, it prevents water from flowing into the tank.

Quick Fix

Simply turn the supply valve counterclockwise to allow water flow. In case the pipes are old and worn out, call a professional plumbing company to repair your damaged pipes.

Poorly Positioned Trip Assembly

The trip assembly connects the toilet tank to the flush handle. According to some pro plumbers, when poorly positioned, the trip assembly blocks itself, therefore, interrupting the flush cycle. Your toilet will fail to flush correctly thus; the bowl will not fill.

Trip Assembly Toilet
Trip Lever

Quick Fix

Simply open the toilet tank lid and inspect the positioning of the trip assembly. In case the trip assembly is broken, worn out, bent, or damaged, replace it.

To replace a broken trip lever, you can detach the flapper chain/clip, and then reconnect the new trip lever to the handle and clip.

The Float Ball Maybe Low

This is the other reason your toilet bowl never fills with water after every flush. The toilet tank always contains water most of the time and once you flush the toilet, water flows to the toilet bowl.

Float ball

The float ball floats in the toilet tank. When water attains the peak level in the tank, the float ball should prevent water from flowing in by adjusting the float arm.

In case the float ball is low, this may prevent water from flowing into the tank. The float ball might also be worn out resulting in your toilet tank not filling up which will result in an insufficient supply of water to the bowl thus a low water level.

Quick Fix

To fix this issue, simply adjust the float ball by bending the floating arm. This will increase the amount of incoming water. In case your float ball is worn out, purchase one from a local plumbing outlet and replace it.

Effects of Low Water level in the Bowl

First off, with low water levels in the toilet bowl, it means the water seal has been broken and there will be an influx of scents in the bathroom.

You will not have the barrier that protects you against bad smells and toxic gases in the drain. This can be a safety and health hazard.

Secondly, the low water level may affect how your wastewater leaves the toilet. Normally, water flushed from the tank will mix with the water in the bowl and carry away the waste. But without water in the bowl, there can’t be the wash away effect.

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