How to Fix a Continuously Running Dual Flush Toilet? [DIY]

A dual flush toilet is specially designed to save water with its low flush option.

But it can be so annoying when your dual flush toilet begins to waste water by running water continuously.

how to fix a running dual flush toilet

If you don’t repair a continually running dual flush toilet right away, you’ll lose money on water and might be forced to pay higher utility bills.

The good news is, you can fix a continuously running dual flush toilet on your own without having to hire a professional.

All you need is a few tools and to follow the steps outlined below.

Why is My Dual Flush Toilet Running Continuously?

When you know the reason(s) why your dual flush toilet is running continuously, then you can apply the right fix.

Below are some common reasons for a continuously running dual flush toilet:

1. A Bad Seal

This is usually the most common cause of a continuously running dual flush toilet.

Unlike the normal flush toilets that use a flapper valve, dual flush toilets use a rubber seal. The seal is located under the canister flush valve.

Being rubber, the seal can become warped, cracked, worn out, or hardened over time. It can also misalign or become dirty and slippery due to mineral or debris buildup.

When any of these problems occur, the seal will no longer work properly. In most cases, the seal will leak water, causing water to run continuously.

2. A Clogged Fill Valve

Another reason for a continuously running dual flush toilet can be a clogged fill valve.

The fill valve can get clogged with dirt, debris, or mineral buildup and malfunction. A malfunctioning fill valve may not shut properly after the tank is full.

This will cause water to overflow and the excess water will go into the overflow tube and continue running into the toilet bowl.

3. A Broken Fill Valve

Unlike the normal flush toilets, dual flush toilets feature fill valves with a zip tie.

The fill valve connects with the toilet tank using the zip tie. The zip-tie locks the bottom of the fill valve firmly in place in the tank.

However, the zip tie can break or wear out over time.

Once this happens, the fill valve will no longer be firmly locked. It will wobble and water will pass through it.

This will cause the toilet to run continuously. Aside from the zip tie, other parts of the fill valve can break too causing the same issue.

4. A Misadjusted Toilet Float

The toilet float opens and shuts the fill valve to regulate the amount of water in the toilet tank.

Normally, the toilet float should be properly set so that the level of water in the tank is about a half-inch below the overflow tube.

However, a misadjusted toilet float – one set higher – will allow more water into the tank above the overflow tube.

The excess water will continuously run down the overflow tube into the toilet bowl.

How to Fix a Running Dual Flush Toilet?

As you know the reasons behind the issue, let’s consider how to fix these problems to stop your dual flush toilet from running.

The Solution to a Bad Seal

As stated earlier, there are several different reasons why your toilet seal would stop working properly. Irrespective of what the reason is, the following steps should be followed before going over any other methods.

Because in most cases, it’s just the washer in the flush valve that gets damaged and causes this kind of issue.

So, here we go-

  1. Shut the water supply to the toilet tank and flush the toilet to completely drain out the tank.
  2. Gently remove the lid.
  3. Hold the canister flush valve firmly and gently turn it in a counterclockwise direction to remove it.
  4. Check the seal properly to see if it is warped, cracked, worn out, hardened, clogged, or misaligned. You may need to remove the seal from the canister flush valve by pulling on it to better inspect this.
  5. If the seal is damaged, the only solution is replacement with a new seal.
  6. If it is clogged and dirty, wash it with water or clean it with vinegar. Handle it gently to avoid warping in the cleaning process.
  7. If the seal is misaligned, adjust it to its right position for a perfect and leakproof seal.
  8. Once you’ve fixed the old seal or gotten a new one, slide it on the canister flush valve.
  9. Fix back the valve by turning it in a clockwise direction.
  10. Gently replace the lid and open the water supply.

Fill the tank fully and inspect it carefully. If you have done everything right, the problem of a continuously running dual flush toilet should be fixed by now.

The Solution to a Clogged Fill Valve

If the problem isn’t with a bad seal but a clogged fill valve, then try the following:

  1. Shut the water supply to the toilet, flush the toilet, and remove the tank lid gently as usual.
  2. Hold, turn the fill valve counterclockwise, and lift it to remove it. If there is a mounting nut, remove it with an adjustable wrench.
  3. Check for debris and mineral buildup. Remove it using a small brush or tweezers, whatever may be effective in doing so.
  4. Once you have completely removed the debris and mineral buildup, replace the fill valve.
  5. Open the water supply and fill the tank.
  6. Carefully check if your toilet no longer runs.

The Solution to a Broken Fill Valve

If a broken fill valve is the problem, the best solution is to replace it with a new one. Though you may try to fix the broken valve to see if it works it won’t hold up for long. Here’s how to replace a broken fill valve:

  1. Again, shut the water supply, flush the toilet, and open the lid.
  2. Gently remove the toilet float ball, if any. The float cup or cylinder doesn’t need additional removal as it remains attached to the fill valve.
  3. Turn the old fill valve in an anticlockwise direction and lift it to remove it. If yours is held by a mounting nut, carefully loosen the nut with an adjustable wrench.
  4. Set the height of the new fill valve to about an inch higher than the overflow tube.
  5. Fit the new fill valve into its place and turn in a clockwise direction. If applicable, tighten the mounting nut.
  6. Reattach the refill tube to the overflow pipe.
  7. Open the water supply and fill the tank
  8. Carefully check to ensure that the new fill valve is working fine.

If it’s not working, you need to remove the fill valve and reinstall it again carefully. Check the rubber gasket underside while installing. Sometimes, it goes missing and water keeps dripping from the supply connection.

The Solution to a Misadjusted Toilet Float

Finally, if you have applied all the solutions above and nothing seems to work, try this last one. Readjust the toilet float and see if that fixes the issue. Here’s how to go about is it:

  • Shut the water supply and flush the toilet.
  • Carefully remove the lid and keep it somewhere safe
  • There is a long plastic screw vertically along the toilet float. This screw adjusts the height of the toilet float, which, in turn, determines the level of water allowed in the tank.
  • Turn on the water supply and start filling the tank. Use a screwdriver to adjust this plastic screw gently in an anticlockwise direction. Adjust the screw until the new water level is about an inch below the overflow tube. There would no longer be excess water.
  • Put the lid back and enjoy a perfect dual flush toilet tank.

Using Dual Flush Toilet Repair Kit

If the problem still persists, you need a dual flush toilet repair kit, which is easily available in any hardware store.

The kit comes with easy-to-follow instructions and all the required tools to fix your toilet tank.

These kits are simply the replacement of the whole flush system inside the toilet tank.

So, you can rest assured that the issue will be gone if you can follow the installation instructions correctly.


A continuously running dual flush toilet can be quite annoying, not to mention the wastage of water. The good news is that it’s usually an easy problem to fix. Most of the time, it’s either a problem with a seal or a fill valve.

In this article, we have gone over some of the most common causes of a continuously running dual flush toilet and how to fix them. We hope you found this helpful and that your problem will be fixed in no time!

If you are feeling that a video guide might have helped you in the process, follow this-

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