Why Is My Toilet Tank Not Filling

Not having enough water in the toilet tank is frustrating in that you don’t get a complete flush after using the toilet.

That may force you to linger in the toilet some more as you wait for the tank to fill up for a subsequent flush. It’s both embarrassing and frustrating.

The reasons why your toilet tank is not filling up include a poorly adjusted fill valve, poorly positioned floater, low water pressure or a bad trip assembly.

You can fix a slow-filling toilet tank by readjusting the fill valve and the float rod. Clean the inlet pipes to make it fill faster.

Quick Fixes: A running toilet or one whose tank doesn’t fill up quickly can be solved through the following:

  • Readjusting the float rod
  • Readjusting the fill valve
  • Cleaning the fill valve
  • Readjusting the trip assembly
  • Cleaning the toilet tank.

What Causes A Toilet Tank Not To Fill Up?

tank filled with water

Finding the reason behind your toilet tank not filling up properly is the first step to solving the same. A majority of these solutions can be undertaken as DIY at home within a few minutes.

Normally, the toilet tank should fill up in a minute or two after flushing the toilet. If this isn’t the case, there is an issue with the structure of the tank, or the water coming in.

If you want to skip these problems altogether you can buy no tank toilet.

The complete list of the causes behind this has the following causes:


The water level in the toilet tank is kept at a certain level by a floater mechanism. This mechanism works by floating a ball on the surface of the water.

As the water fills the tank, it raises the ball with it. Being attached to the float rod, the floater then reaches a certain level where it stops any further flow of water into the tank.

If the ball is hanging too low, it’ll let very little water into the cistern. This can be the case when the ball is damaged or has a puncture such that it has the weight of the water inside it.


fill valve malfunctioning

If the position and structure of the floater ball isn’t an issue, then it could be the fill valve which is either poorly adjusted or not working.

The fill valve is located at the point where the float rod starts (away from the float ball). This valve has adjustments that determine how much water will enter the toilet tank. If it’s been adjusted too tightly, it’ll let very little water into the toilet tank hence it won’t fill completely.


If there’s just too little water pressure from the inlet to your toilet tank, it’ll take quite a while for the tank to fill between flushes. This can be due to faulty pipes or even dirt in the piping system.


The trip assembly refers to the mechanisms from the toilet handle, the trip lever all the way down to the valve seat where water leaves the toilet tank and into the toilet bowl. If any part of this setup is faulty, the tank won’t fill completely.

The most likely culprit is the flapper chain. When it’s too tight, it’ll leave space in the valve seat (below the flapper) through which water can sip and empty the tank even when the toilet isn’t being flushed.


clean debris in toilet tank

If your toilet has been in use for a long time, it could be that the tank has filled up with debris that could be taking up space in the cistern. Kids may also throw items into the toilet tank if they find it open.

You may have one or a few of these causes occurring together. Checking each part mentioned will reveal the actual cause(s).

5 Ways To Fix A Slow-Filling Toilet Tank

If, after checking your toilet tank and the other parts connected to it, you’ve identified the issues above, you then need to carry out the following procedures to restore your tank’s normal function:


tank with floater

In most toilets, the float rod is made of bendable metal.

As such, if you find that the floater ball is too low into the water, one solution is simply bending the rod upwards to lift the ball such that it allows in more water before stopping the inlet. If the toilet is a tabbed one, lift the float manually.

If the rod is a plastic one or too rigid to bend, you’ll need to check whether the attachment of the ball to the rod has a mechanism for changing the elevation of the ball from the water directly. Some have two points of attachment for the ball above each other.

If the ball has a puncture, you’ll need to get a new one as its function will be compromised.


The fill valve can be adjusted with the adjustment screw located at the beginning of the float rod. The screw can be directly on top in which can you can use a screwdriver to adjective it, or on the side whereby a hand twist can do the trick.

Given that the issue is the toilet tank having too little water, ensure you turn the fill valve in a direction that provides more allowance for water to get in. This will ensure that the float ball is freer and thus allows in more water before locking the fill valve.

Be careful not to release the fill valve too much as it may lead to a leaking toilet tank due to overfilling.


man checking inlet pipes

If it’s a case of low water pressure into the toilet tank, you can check the piping from the main tank to the cistern for problems. At times, it’s just a leaking pipe that needs refitting.

Other times, it could be a partially blocked pipe with sediments in it. The worst case is when the pipe is broken and needs to be replaced.

For pipes with sediments, lightly hitting them on the side (in the exposed sections) can dislodge the dirt. Otherwise, forcing water through them at a high pressure can solve the problem.

There are commercial solvents that can be poured into pipes to clear debris in them. At home, you can use bleach or a mixture of white vinegar and baking soda to clear the debris.


Check if the toilet handle is stuck, if the trip lever is broken, and if the flapper chain has the right amount of tightness. The chain should just be tight enough to open the flapper valve when the handle is pressed, and loose enough to let the flapper valve stay closed when the toilet isn’t being flushed.

Also, check the integrity of the flapper valve and the valve seat to ensure that no water is sipping out of the toilet tank.

If any of these parts isn’t in working condition, find its replacement for the toilet to work properly again.


Start by shutting off the inlet to the toilet tank then flushing the toilet to clear out all the water from the toilet tank. Follow that by removing the flapper from the assembly.

Clean each part then let water into the tank again. Wash the walls of the tank as the water carries the dirt to the toilet bowl. Any parts with sediments should be cleaned in this stage.

Next, shut off the water inlet then return the flapper into place. Let water into the tank then observe if it fills up properly or not.

These fixes should restore the workings of the toilet tank. After every fix, let the water run into the toilet tank and observe the level and time taken to fill the tank. It should take about a minute to fill the tank and the water level should be just below the drain pipe.