A normal toilet mechanism is to flush the toilet- water goes down to bowl-then flush away to the drain. Reversely toilet tank begins to fill with water for the next use.

But while the flush component shows some issues, either tank water getting low or leaking from tank to bowl.

One day, I freak out to see my toilet water Level in Toilet Tank Drops and immediately call a plumber. I lost so many bucks to know why am I losing water in my toilet tank.

He explained everything to me. After knowing the cause, I almost fainted due to a silly job. Why had I not researched before?

I don’t want to go same you. You can do it yourself by spending a few bucks instead of a hundred dollars.

As if you read it till now. It means, unfortunately, You have the same problem with your toilet water level in the toilet tank dripping slowly.

No, worries. Let’s check out the reasons and how to the toilet that water level in tank drops slowly.

Why is Your Water Level in Toilet Tank Drops Slowly and How to Fix It

There are a few reasons to water level suddenly drops from the tank. Including

  • Flapper
  • Overflow Tube
  • Flush Valve
  • Tank Gasket
  • Crack Tank

Follow the table of signs and symptoms, fix according to cause.

DefectSign & SymptomsFix Idea
Flapper tight
Faulty Flapper
Slowly Drain
Neither slow nor too Fast Flow
Adjust Chain Height
Change into New
Overflow TubeDrain continuous & Hiss soundReplace with new
Flush ValveDrain Continue, Leak behind the tank, seatChange
GasketSame sign with more waterChange into new
Crack TankSlowly drain, water drop floor, seat, not fillChange into a new tank

Cause NO.1- Toilet Tank Losing Water But No Leak Due to The Flapper

The very first cause for losing a toilet tank water is the flapper. Either it is tight to sit or damage the sealing.

Tight Flapper

While you see the water level slowly drop from the tank, at first check the flapper seal. 

The flapper is the seal component that is placed on the flush valve, which allows the water to flush while sealing the water when not in use.

The flapper connects with the flush lever by one chain, and the chain length determines how close and open the flapper is while used or not handled.

How to Fix a Tight Flapper

  1. Turn off the water supply to the toilet
  2. Flush completely
  3. Observe the chain. There is a clasp present holding the chain between the lever arm and flapper.
  4. If possible, untied the flapper and clean the base.
  5. Remove the clasp or hook, peg one step forward to increase the chain length. So the chain length becomes a long little bit.
  6. Long-chain flapper now seal is firm.
  7. Turn on the waterline, allow the water to fill the tank. Observe after 30 mins. See what is happening, water drop or stop.
  8. If it discontinues, congratulation. You don’t need to spend a single penny, and the problem is solved.
  9. If, yes Go for the next step. Change the flapper.

How to Fix a Defect Flapper to Stop Water Leaking From the Tank

Defect flapper is another reason to decrease the water level in the tank. By changing the flapper, you may resolve the problem.

How To Change a Flapper

Changing a flapper is as simple as boiling the water. Just buy one flapper according to your model number or universal flapper.

  1. Turn off the water supply to the tank.
  2. Flush completely
  3. Remove extra water by sponging.
  4. Now, unhook the clasp connected with the chain.
  5. Disconnect the chain from the flush lever arm
  6. Remove the flapper and clean the baseline with a cloth.
  7. Examine the sealing place with a flashlight, presence of any debris or lime deposition
  8. After cleaning the base area. Simply place the new one, peg the two arms with a flush valve.
  9. Then connect the chain as see before it removes
  10. Check the length of the chain, too tight again leaking, and too loose not flush properly.
  11. Flush several times and adjust the height of the chain and finally observe over 30 minutes. If any development the condition or not.

If your flapper has made the issue, changing or adjusting can solve the problem.

Note- If you have recently changed your flapper, adjusting the height is significant to know either its flapper or other cause. Don’t go for another new one. Check other possible reasons.

Cause NO.2- Why am I Losing Water in My Toilet Tank? Is it For the Damage Overflow Tube!

Overflow tube generally does not break or crack very quickly. But due to water pressure, it happens sometimes.

The overflow tube is present in the middle of the tank. It is comparatively broad and has a long tube. 

The overflow tube is placed over the flush valve and attached to the flapper.

How to Replace an Overflow Tube

Buy a new overflow tube, then start the process-

  1. Turn off the water supply line, then flush the toilet once
  2. Pull out the overflow tube gently
  3. Match the height of the previous one
  4. Place securely at the position
  5. To check, turn on the water, allow the water to fill the tank, and then as I mentioned before.

Cause NO.3 Drops Water Level from Tank Due To Tank Gasket and Flush Valve

The flush valve is mounted at the bottom of the tank and ranges from 2 inches to a 4-inch flush valve.

Larger flush valve, high volume water, including water pressure release to the bowl.

After a long time of use of the toilet, the flush valve may have cracked, or the seal can break even mineral can ruin the valve.

This is why the water of the tank slowly sinks and your tank becomes empty.

The same happens for the gasket. The gasket is placed beneath the tank, secure a tight seal tank and bowl. The gasket is rubber material, so it may sometimes be worn out.

How to Change Flush Valve and Gasket

  1. Buy one flush valve according to size and model or universal flush valve.
  2. Shut off water line, flush completely
  3. Sponge out the rest of the water.
  4. Take out the flapper.
  5. Now beneath the tank, you can find some nuts ( most toilets have two tank bolts, some have three)
  6. Unscrew them, so you can take off the toilet tank.
  7. Now, can see the gasket right there(black, blue, or red) take off that too.
  8. As you see, you have a very large plastic nut on the bottom of the flush valve. So got a large channel lock and unscrew it.
  9. Now pull the whole flush valve and change with the new one.
  10. Place the new, it’s placed, screw down the large nut.
  11. Tie everything that you just unscrew from the tank
  12. After placing the tank as before-connect the waterline and waiting to fill and observe for leak

Cause NO.4 Tank waterfall and leak due to Crack Tank

Oh! my God. If this happens. Unfortunately, you have to change the whole tank.

If you have a two-piece toilet, only replacing the tank is sufficient. However, if you have a one-piece toilet, the entire toilet should be changed.

Check- Best One-piece toilet all the time.

Tricks to know Where is the Leak Coming From 

  1. Take one food color. (red, blue, green, whatever you have) 
  2. Pour a few drops ( two-three is enough)
  3. Now see where the coloring water is going on the bowl or the floor.
  4. Then match
Color In BowlFlapper, Overflow tube issue
Color on FlowGasket & Flush Valve Problem
Color on Floor, behind the tank, seatCrack tank, Gasket

Final Thought- Water Level In Toilet Tank Drops Slowly

The problem you are currently dealing with cannot be avoided. After you’ve identified the problem, you must take action.

You see a well with water slowly flowing into it. Is the water dripping on the floor or running into the bowl?

Examine the table I created and solve the problem as it is.

I’m hoping you’ll be able to address your problem on your own.

FAQs- Drain Water From Tank

Q1. How do I know if my toilet flapper is bad?

To know your flapper is bad, observe the toilet. Either toilet leaking from the tank to bowl or have flushing issue.