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 especially after flushing is a common toilet problem that indicates there could be a clog (partial or full), a blockage in the vent pipes, an issue in the tank that restricts water from reaching the needed water level, or a crack in your toilet bowl that’s leaking water from the bowl.

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.

Poorly Placed Fill Valve

The fill valve usually controls the volume of water flowing into the tank once you flush the toilet. In case it is poorly placed, then the tank will have a low water supply, therefore, your bowl will not fill.

fill valve

Quick Fix

There are two types of toilet tanks in the market. You either have a tank that has an adjustable cylinder or one with a float ball. Both tanks have fill valves; the only difference is how you inspect whether the valve needs adjusting. Here is how to fix both tanks:

  • In case your tank has a float ball, inspecting the fill valve requires a flat- head screwdriver. First, place the screwdriver in the adjustment screw found on the fill valve then turn the screwdriver clockwise to allow more water into the tank. Flush the toilet after adjusting the valve and inspect whether you have achieved the required water level. Keep adjusting the valve until you are satisfied.
  • If your tank has adjustable cylinders, simply locate the fill valve then pinch the float clip that you can see beside the valve. Slide the fill valve upward to allow more water into the tank then flush the toilet. You will have solved the problem and the bowl will fill correctly.

Low Water Pressure

You might wonder why your toilet is in the perfect state yet the bowl never fills with water.  This is often a result of low water pressure in your house. It can also be due to poor piping in your plumbing system.

In case you experience water problems and you notice a high-pitched faucet noise, then your toilet bowl might fail to fill upon each flush. Your pipes might be worn out and might be leaking, therefore reducing water pressure.

Quick Fix

If the low pressure results from poor piping, you should contact a plumbing professional. They will effectively determine the root cause of low water pressure and correct it.

In case the pipes are old and worn out, the plumbers will fix the problem by replacing the pipes with new ones. You should never play around with drainage systems. Always contact professionals in such cases.

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.

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, you will have to replace it.

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 you may be going on in your toilet, you should flush the toilet.

The water may overflow a bit up to the rim of the toilet, after which it will sip slowly by slowly until it passes the normal water level on the bowl. Sometimes it could even drain the toilet completely. Here’s where some good unclogging techniques come into play.

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

  • Fill a five-gallon bucket with water and pour it quickly into the bowl. This will release any blockages from the trap way. Check for any water backing up.
  • Wear rubber gloves and use your hands to locate any blockage in the pipes. This is best for large pieces of waste such as diapers, stuck in the drain.
  • Plunge or auger the toilet to ensure you really unclog any waste.

Blocked Sewer Vent Pipe

The sewer vent pipe depends on air/ sewer gas to allow for the free-flowing of air in 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. This means the air seal has been broken and no more suction. Water may return to the bowl, but just a little.

If you stay somewhere that’s filled with forestry, 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.


Use a ladder to get on the roof and clean and clear the plumbing vents. You need to allow for the free flow of air in the venting system to ensure the plumbing system is operating at the right 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.

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.

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.

Cracks in the toilet are very hard to find and you may not even find let alone see the crack in the toilet.

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 somehow and dripping to the floor. This is a very serious problem compared to the other causes above.

Quick Fix

Lastly, you will need to replace the cracked toilet bowl. You can opt to repair the bowl instead of buying a new toilet unit. However, the bowl can crack anywhere, at the base, the back, or the sides.

And in most cases, you won’t find the crack. Hence, getting a new toilet and replacing it is the best option for a long term solution.

If you happen to see a crack in your toilet, you can use a sealant or caulk to coat the crack. Use a good silicone sealant to cover the area, and repeat whilst pushing the sealant into the crack. Ensure it’s waterproof and can do the job effectively. This will ensure it dries in place to prevent another leak.

Even though the sealant will do the job, it’s only temporary, meaning you may have to fix the toilet again in the future. Your best guess is to replace the toilet as a whole. Call in a plumber to have them fit it in properly and use caulk to seal the base. This should fix your problem if you were experiencing leaks.

The Float Ball May be 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 to insufficient supply of water to bowl thus 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. Also, consider consulting a professional to fix this issue since you might fail to adjust the arm correctly.

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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