Why Does My Toto Toilet Keep Running? (4 Reasons Explained!)

Are you having problems with your Toto Toilet? One major issue with Toto toilets, like any other, is water overflow. Then you wonder,’ why does my Toto toilet keep running?’

Your Toto toilet could be running because of a defective fill valve that fails to control the amount of water filling the toilet tank, an overly raised float height, or a faulty flapper or flush valve that needs replacing.

Note that the biggest risk with a Toto toilet that keeps running is that it can lead to lots of water wastage and expensive water bills. According to EPA, an unrepaired running toilet can waste one gallon every hour.

That’s much water if you ask me! And much money too!

So, act first to fix the issue, and it starts with identifying the source of the overflow. If you cannot, then calling an expert plumber is advisable.

But before you do, how about you try the tips that I’ll share with you in this post? They are practical and will fix most issues relating to a running Toto toilet.

But first, let’s first look at how your Toto toilet works.

How Your Toto Toilet Works

Usually, water enters the Toto toilet tank through the fill valve. As it fills the tank, the flapper prevents it from running to the bowl.

And when water fills the tank and reaches a certain height, the fill valve shuts off, stopping more water from entering the tank until you flush.

Once you flush, the flapper opens and releases water to the bowl through the toilet’s rim holes, pushing the waste down the main drain.

Note, however, that if there is an issue with the fill valve, float, flapper, or flush valve, your toilet may keep running until you fix it or shut off the water.

Let’s now look at how all these issues affect your toilet.

Why Does My Toto Toilet Keep Running?

Generally, your Toto toilet could be running because of any of these four reasons:

1. Defective Toto Toilet Fill Valve

Under perfect conditions, a fill valve controls the amount of water that gets into your Toto tank until the water reaches the set level. But if the fill valve is dirty, broken, or just too long, it won’t execute its job correctly, and so the toilet is likely to keep running.

The Fix

Each issue with the fill valve requires a different fix. Let’s discuss them briefly:

a) Dirty Fill Valve

If the flush valve is dirty, you should clean it using these tips:

Turn off the toilet water supply
Flush the water that is in the tank
Take a piece of cloth or sponge to suck the reaming water inside the toilet tank
Remove the fill valve and clean off any dirt deposits
Place the fill valve back after cleaning
Turn on the toilet water supply and wait for the tank to fill to check for leakage

b) Broken (or Worn Out) Fill Valve

A broken fill valve is one of the reasons behind a Toto toilet running constantly. The fix for that is getting a replacement flush valve and then fitting it using these tips:

Turn off your toilet water supply and drain all the water in the tank until its dry
Using a screwdriver, unscrew the old fill valve from the locking nut at the bottom of the tank
Take the new fill valve and adjust it to a perfect height of your Toto tank water level
Remember, the threaded fill valve end should go at the bottom of the tank
Lock the nuts tightly, ensuring to create a tight seal
Turn on your water supply, and if the installation were a success, water would stop running to the bowl

Overall, if you are looking for the best Toto fill valve to replace your old one, you cannot go wrong with the TOTO TSU99A.X Adjustable Fill Valve (View on Amazon). It’s pretty adjustable to any height and has a universal design, thus likely to fit all Toto toilet tanks.

c) An Extra Long Fill Valve

If your fill valve is too long, it causes a suction effect that pulls water from the fill valve.

So, to fix it, you first need to pull it out and trim it to size using cutting pliers. Once you have the right size, clip it and place it properly around the overflow tube.

2. Overly-Raised Float Height

The typically adjustable float controls the tank’s water level. If it sits too low, it will result in a weak flush. However, if it’s set too high, it will encourage an overflow as the tank is likely to hold more water.

The problem with an overflow is that it causes the water to leak into the bowl via the overflow tube.

The Fix

Adjust the float height to achieve the correct water level. You can do that by adjusting the screws on the float arms

3. Defective Flapper

Generally, a flapper’s job is to close off the toilet flush valve to retain water in the holding tank. However, if the flapper is defective, it won’t help the tank retain water, and the toilet is likely to keep running.

Overall, a flapper can be defective if it’s too long or if it’s worn out. In the first case, the flapper will keep hitting the tank lid and will not let the flapper open fully for a powerful flush.

In the second case, the flapper fails to work completely. Old and worn-out flappers don’t seal well, making water run from your toilet tank to the bowl.

The Fix

If the flapper is too long, consider resizing it using cutting pliers. Ensure you only leave an inch to prevent chain tangling in the tank.

But if you cut your flapper chain and your Toto toilet continues to run, the chances are that the flapper is worn out, and that calls for a replacement.

Here are the steps for replacing your Toto flapper:

Turn off your toilet water supply
Flush the toilet to drain the water in the holding tank
Drain the excess water using a towel or a sponge
Remove the worn-out flapper and replace it with the new one
Turn on your water supply and check if your toilet still leaks

You can buy the Essential Values 3-inch Toto Toilet Flapper if you want a replacement flapper for your Toto toilet. This universal flapper, thus compatible with many Toto toilet models and comes in a quality build.

4. Faulty Flush Valve

If your toilet flush valve is faulty, your toilet tank won’t create a seal to contain the water. One way to tell a defective flush valve is running toilet water. You can also tell if the flush valve is making a screaming sound.

Fix (Toto Flush Valve Troubleshooting)

You should replace your faulty flush valve using these steps:

Turn off your Toto toilet water supply
Flush the toilet to drain all the water
Drain the excess water using a piece of cloth or a sponge
Remove the old flush valve by unscrewing the bolts that hold it in place
Install the new flush valve and tighten it in place
Place the tank-bowl gasket in position
Turn on your Toto toilet water supply
Let the tank fill and then check if there are leaks
If not, the installation was successful

If you want a replacement flush valve, you can consider the TOTO TMT1LN32#CP HET Universal Flushometer Valve (View on Amazon). This flush valve comes in a standard size ideal for replacing many flush valve toilets.

When to Call an Expert

While most running toilet fixes are DIY, a few others require the input of a professional plumber. Sometimes you may not be sure of the issue, especially after going through all the potential culprits. In such a case, you should give an expert plumber a call.

Since plumbers are well-versed with the anatomy of the toilet system, they can diagnose issues that are not apparent to you. Moreover, they have the right tools and know what to buy, saving you from making a wrong purchase.

Why Does My Toto Toilet Keep Running? (4 Reasons Explained!)

How Your Toto Toilet Works