A toilet tank is made to fill up with water whenever it is flashed. The water level is supposed to be about half an inch below the overflow tube that should take approximately 10 seconds to refill. Why then is the toilet tank not filling up?

Some of the problems that might be causing it not to be filling up include a low float ball, a broken chain in the trip assembly, or a plumbing issue where pipes are leaking and rusty. Assuming the pipes are not the problem, most of these issues are easy to repair or troubleshoot on your own.

Here’s what to look out for and how to go about fixing it.

Check How the Float Ball Is Seated

Whether your toilet is the old or modern version, it will either have a float cylinder/cup or a float ball. Float cups are usually smaller and are installed in modern toilets, while float balls are found in old models. It is connected to the fill valve and controls its opening and closing.

When your toilet tank is not filling up, this is usually the first suspect you should take a look at. It is supposed to sit above the water and stops the water influx once it reaches its maximum height. It does this by moving its float arm as the water rises to block water inflow. When you find there’s no water in your tank, the float ball is most likely seated too low.

In this case, you need to adjust it using the following steps:

  1. Turn off the toilet’s water supply by reaching for it behind the toilet, and then turn the shut valve clockwise to turn it off.
  2. Hold down the lever for a long time to flush the toilet and get most of the water out.
  3. Remove the lid and place it in a safe place and check if you have a float cup or float ball.
  4. If you have a float ball and it’s seated too low, check where the float arm connects to the fill valve and turn the screw clockwise to raise the water levels.
  5. If you have a float cup, there is a long plastic screw alongside and connected to the float. Turn the screws clockwise using a screwdriver to raise water levels.
  6. As you make the adjustments, turn the screws minimally and in stages as you turn back on the water supply until the water level is halfway below the overflow tube.

Adjust or Replace the Fill Valve

The fill valve connects the toilet tank to the water supply line. On the inside, it is connected to the toilet float and refill tube. When you flush the toilet, it is responsible for filling up the tank.

The toilet float lowers to the bottom hence opening the fill valve, and water starts filling up. A faulty fill valve will cause water not to fill up, and in most cases, this results from debris accumulation, a worn-out seal, or the valve is too old.

If the fill valve is new and it’s still not filling up, debris accumulation could be the problem. You can easily fix this by yourself by following the following steps:

  1. Shut off the water supply and flush the toilet.
  2. Hold the bottom of the fill valve’s shaft on the one hand, and use the other to turn it 1/8 counterclockwise and remove it.
  3. To prevent water from splashing, place an empty cup over the fill valve and turn on the water supply. Its pressure will force out the debris.
  4. Once it’s unblocked, place back the fill valve cap.

If your fill valve is worn out/old, the best option is to replace it. Here’s how to go about replacing your fill valve:

  1. Shut off the water supply and remove as much water by flushing the toilet and holding the lever down.
  2. Turn the coupling that connects the toilet tank to the water supply line counterclockwise to remove it hence disconnecting the water supply.
  3. Turn the lock nut counterclockwise to uninstall it.
  4. Detach the fill tube from the overflow tube and lift away the fill valve.
  5. Thoroughly clean the area where you will place the new fill valve, slide it in, and screw the lock nut in.
  6. Connect back the supply line, install the fill tube to the overflow tube, and turn on the water supply.
  7. Adjust the water levels if required.

Adjust or Get a New Toilet Flapper Flush Handle/Chain

When you find that water keeps running, but it is not filling up in the tank, the flapper could be the problem. It’s a seal found at the bottom of the tank; once you flush, it opens up to allow water to enter the bowl and closes afterward for the toilet tank to hold water and fill up for the next time you flush.

A lift chain connects the toilet handle and the flapper. If the chain hooks to other parts of the cistern or is too tight, the flapper unseats, causing water to run continuously without filling.

Sometimes, the flapper will not seal due to debris and mineral accumulation. Also, if the chain or flush rod is too long, you’re likely not to get a full flush. Cut off excess rod links, and be sure to leave just an inch to prevent tangling.

Adjusting the chain linkage, leaving a bit of slack, or cleaning the flapper and flush valve can solve this problem. However, if the flapper is worn out, it’s best to replace it by following a few steps:

  1. Turn off the shut valve and flush the toilet.
  2. From the flush handle, remove the lift chain.
  3. Detach the flapper from the overflow tube by removing the pegs, holding them together, and lift it.
  4. Thoroughly clean the part where the flapper will sit.
  5. Peg the lift chain to the flush handle.
  6. Turn the water supply back on and ensure it is not leaking.

Check the Trip Assembly and Replace It

The trip assembly is the part that connects the tank and the flush handle. When the lid is placed, this part may get blocked hence disrupting the flush cycle. You can establish if this is the problem by lifting the lid and checking if the trip assembly is bent, worn out, or broken. If either of these is the issue, find a close replacement or the same from the store.

Check the Fill Tube for Any Damage

This is a small pipe that is connected to the vertical/overflow tube and fills the tank whenever you flush. If it is disconnected, the valve shuts off the water supply before there is enough in the tank. Check to see whether it’s unclipped and fix it. However, if it’s broken or worn out, get a replacement.

Switch Damaged Overflow Tube

This is the large tube found in the cistern’s mid-section that allows excess water to channel to the toilet bowl and prevents overflowing. Although it is not common, this tube can crack, therefore channeling more water to the toilet bowl continuously.

If this is the case, your cistern will not fill, but water will keep running. To replace it, just pull it out and place the new one. Ensure the new overflow tube is the right size.

Check the Water Pressure

Sometimes, there is nothing faulty with your toilet tank; it’s just filling up slowly or not filling up at all because the water pressure is low. Old, rusty pipes that are damaged cause leakages while most are clogged, therefore creating a weak flow of minimal water to your home and toilet tank.

Low pressure not only affects your toilet tank but the entire house. Old homes are more susceptible to this problem, while in new houses, it could be an issue of bad piping. In this case, unless you’re well versed with plumbing, you will need to call in a professional to assist with rectifying the damage.

Check the Shut Off Valve

The first thing to check when your toilet tank is not filling at all is if your shut off valve is open. You can locate it behind the toilet on the wall and open it by turning it counterclockwise. Some toilets have a pull/push valve; in this case, push in the handle to open for water to start flowing in your toilet tank.

  1. If the valve is open, but there is no water running.
  2. Shut it completely by turning it to the right.
  3. Afterward, check the cistern and remove the cap that shuts the fill valve.
  4. Turn back on the water supply and, using a cup, redirect it so that it goes into the tank.
  5. In case the problem persists, shut off the valve and disconnect the supply line from the fill valve to establish if water flows through it when you turn it back on.
  6. If it doesn’t, this is an indication that the valve is blocked.
  7. Use a flashlight to peek and unclog it if possible using tweezers or a hooked wire.
  8. Put back everything in place, and switch on the water supply.

Check for Any Cracks in the Toilet Bowl

Cracks on the toilet bowl, although rare, cause water to leak. You may fail to notice and think it’s your toilet tank. When this happens, purchase a new toilet bowl and call in a professional to replace the old one.

Here is a video on how to fix a leaking toilet tank:

Things to Consider Before Repairing or Replacing Parts of a Toilet Tank

  • Whether you have the technical know-how and time to shop for parts and conduct repairs or call in a licensed professional.
  • Codes that you need to follow regarding your work.
  • Avoid over-tightening connectors like nuts and bolts, as this would damage the cistern and the plastic fasteners.
  • Use care by taping the plier jaws and wrenches to protect the metal fasteners.
  • Ensure safety when removing and placing the toilet tank lid to avoid breaking it.
  • Safety precautions to avoid injuries like cuts and wounds that may be caused by broken and rusted parts. Wear protective and waterproof gloves.
  • Purchase repair parts that fit your toilet measurements.

Bottom Line

Your toilet is a necessary part of the house that is taken for granted until it experiences a problem like not filling up. When your cistern is not filling up, you may start to contemplate whether it needs replacement or it’s an issue that can be fixed. In most cases, these are problems that require a simple fix that you can conduct yourself with a bit of knowledge and skills.

You may also consider future problems that might occur and fix them. If you have a tight schedule, you might consider calling in a professional to handle all the repairs.

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