Toilet Tank Losing Water But No Leak? Fixed!

Your first instinct is to find the leak when your toilet tank keeps losing water. It’s a confusing and, unfortunately, common issue when you can’t find the source of the leakage. Even if it doesn’t look like it, there may still be a hidden leak.

In most cases, the leaking toilet results from a hidden internal leak caused by a faulty fill valve or flush valve system. In an internal leak, water from the tank seeps into the toilet bowl, making it difficult to detect.

This article will explain how to detect these internal leaks and methods for plugging them up.

Why Does My Toilet Keep Losing Water in the Tank? 

Do you know your toilet takes up 30 percent of your water usage? The figure is relatively higher in large households. In fact, a leaking toilet can waste as much as 200 gallons in a day. 

To avoid paying exorbitant utility bills, here’s why your toilet tank keeps losing water. 

Toilet tank losing water

Faulty Flush Valve System

A faulty inlet valve is often the reason why your toilet tank keeps leaking. The inlet valve or flapper is directly above the flush handle. It creates a seal that prevents water from leaking into the inlet valve. 

The seal usually forms a watertight seal and prevents water from leaking into the toilet bowl. However, the seal deteriorates with time, causing water to leak into the bowl. 

Malfunctioning Fill Valve

A fill valve connects the inlet valve to the floating plastic ball in your toilet tank. If the ball or fill valve is faulty, water will overflow into the toilet bowl or outside the tank. A broken or incorrectly-placed fill valve will cause water spills in your toilet. 

External leaks are often easy to detect. In most cases, all you need is to spot the wet area. You have a loose or faulty locknut if you see water pooling at the base of the toilet tank. You also check the washer on the fill valve. 

Sometimes, a defective supply line to the toilet may leak water on the toilet floor and within the walls. Plumbers often advise changing the supply line at least once in five years. 

What Is Ghost Flushing? 

Imagine hearing a toilet flush without anyone using it. It’s scary when it happens in the middle of the night. Don’t fret—your house is not haunted. 

Ghost flushing, also referred to as phantom flushing, occurs when there is a leak between the toilet flapper and flush valve. The defective seal causes water from the toilet tank to seep into the bowl or outside the water tank. 

Ghost flushing may occur every few minutes or randomly. It’s a cause for alarm if it happens every few minutes. Also, you should fix a slow leaking tank before the damage becomes severe. 

How Do I Know If My Toilet Tank Has an Internal Leak? 

It’s not normal for your toilet tank to refill without anyone flushing. It’s infuriating when you can’t pinpoint the leakage.

Toilet flush system

You may see water running along the surface of your toilet bowl. If you don’t see that with the naked eye, you can use the help of dye or coloring to detect it. Using it, you’ll see the dye-stained water flowing into the toilet bowl. 

First, get a dye. Toilet dyes are free at your hardware store. Talk to the store clerk if there’s none on display. 

Note: Get two toilet dye capsules for a brighter color. Alternatively, a food dye or coloring is also suitable for this process. 

Pour the dye capsules into the toilet tank and wait. After waiting a few minutes, expect one of two outcomes:

  1.  The colored water stays in the tank, indicating that there’s no internal leak. 
  2. The water in the toilet bowl gradually becomes colored, signaling a leak.

Congrats on getting to the first half of the process. Now, it’s time to find out the root cause of the leakage. Here’s a simple, sure-fire method to detect it:

Water enters the bowl via the open flapper valve and the fill tube. The fill tube is situated under the rim of the toilet bowl, and it’s responsible for those tiny jets of water when flushing. 

On the other hand, the flapper directs water flow through a siphon jet into the deepest part of the toilet bowl. 

There’s a problem with the refill tube if there are dye stains on the sides of the toilet bowl. However, the flapper is defective if there are no dye stains around the bowl. 

How Do You Fix a Toilet That Keeps Losing Water Without a Visible Leak?

Why do you need to do this? You’re losing thousands of gallons of water every year while racking up a higher utility bill. Don’t waste time when you notice your toilet tank water disappearing without a leak.

Replace the Toilet Flapper

You can start by replacing the toilet flapper. An incorrectly misplaced flapper is often the cause of water leaking into the toilet bowl. So, visit your nearest hardware store to get a replacement. And no, you don’t need to call a plumber. There are different flapper sizes, but it’s preferable to choose a 2-inch flapper. 

How to Install a New Flapper to Stop Internal Toilet Leaks 

  1. Take off the toilet lid;
  2. Reach into the toilet tank and remove the old flap (you don’t need to turn off the water supply).
  3. The substitute flapper has different settings: Use the highest setting to minimize water use and a lower setting for a powerful toilet flush. 
  4. Attach the chain on the flapper to the flush lever, and you’re good to go! 

Replace the Fill Valve to Stop Internal Toilet Leaks

Hardware stores sell the fill valve as a complete kit. To stop internal water leaks:

  1. Unscrew the fill valve using a wrench.
  2. Replace the defective valve with a new one.
  3. Adjust the valve height to ensure it is at least one inch above the water level. 

Note: Switch the water supply before removing and replacing the fill valve. 

toilet fill valve


DIYers, save yourselves the extra costs in utility bills by utilizing these simple solutions to the internal leaks. You can also share this article with anyone with a similar problem. Remember, DIYers’ got to stick together.