Common Dual Flush Toilet Problems + Troubleshooting

Some of the most common dual flush toilet problems include water constantly running and leakages, malfunctioning of the flush mechanism and problems with water levels either in the toilet tank or the bowl.

Below are details of the issues and how to troubleshoot them. Also, find out the known disadvantages of double flush toilets

Water Keeps Running after Flushing

Water constantly running or filling the toilet tank suggests that the system is either allowing water to pass through the flush valve flapper or that the water within the tank is going into the overflow tube.

A leak might be slow and difficult to detect, leaving you wondering why your water costs are so high despite the fact that your usage remains constant.

By putting a few drops of dye or food coloring into the tank, you can quickly determine whether the extra water is pouring into the toilet bowl or the overflow tube.

The problem is most likely with the flush valve or flapper mechanism if colored water streams into the toilet bowl but if the water in the toilet bowl remains clear, the problem is most likely with the fill valve or overflow tube system.

Check to determine if any of the following issues are the source of the problem if the water leaks to the bowl:

  • When a dual flush toilet leaks, it’s mainly due to a worn out flush valve seal at the base of the center canister. To remove old parts, follow the manufacturer’s instructions. Many manufacturers include repair videos on their websites that show you exactly what parts you’ll need to fix your model. Some parts are sold as kits, while others are sold individually.
  • Constant flowing water in both standard and dual flush toilets is also frequently caused by malfunctioning flappers or seals due to wear or misalignment. This rubber or silicone piece may degrade with time, becoming brittle or porous , or the flapper might just be merely misaligned, allowing water to leak through which is easily fixable.
  • Zip ties are fitted in most dual flush toilets to keep the overfill tube in place. This could break over time, so you’ll have to replace it if it does. To eliminate persistent leaks, zip ties can be replaced or a second one can be added. When the tube base wobbles constantly, this can happen.
  • The presence of foreign elements in the tank water, such as dust, pieces from broken parts, and other debris, may cause some of the flush mechanism’s functions to be altered.

The most prevalent issue caused by the presence of debris in the water is leading to the failure in the valves and the flapper functions. The majority of them are constructed of rubber and silicone and are supposed to press against each other to form a flawless seal; however, if any debris gets in between, compatibility fails and leaking occurs.

If you discover the problem is with the fill valve or overflow tube, you can simply identify and manage it as shown in the last part of the post.

Malfunctioning of the Flush Mechanism

Your dual flush toilet buttons or lever could actually fail due to either a direct problem on them or indirectly, that is the other mechanism inside the tank. Check the flush mechanism inside the tank if the toilet is not flushing properly. The toilet will not flush if the flush valve chain has gotten detached from either the flush lever or the flush ball. Make sure the chain isn’t too slack so the flush ball lifts when the toilet is flushed.

Dual flush system picture
Dual flush system

Adjust the water level in the tank using the float if the toilet isn’t flushing well. To allow full pressure for the flush and to fill the tank faster, fully open the water supply shut-off valve. Check to see if the increased pressure aids in flushing.

If the toilet is generating too much noise when flushing, Close the water supply valve slightly to reduce the pressure entering the flush. Try a test flush and adjust until the flush is satisfactory.

Water Level Problem in the Toilet Bowl

If the water level in your toilet’s bowl sits higher than normal, or overfills with water after flushing the cause may be a partial or complete clog in the toilet’s drain.

You can confirm or test out a clog in your toilet bowl by pouring a bucket of water into the bowl. If the water level sits high it means there is a complete clog and if it drains slowly the speed will tell you the size of the clog.

When there is a clog in the drain, some toilets might not overflow, but others do overflow even when there is only a partial clog.

One of the main worries, when the toilet bowl fills up with far too much water, is that the water will run out over the bowl’s rim and out onto the floor, posing a health hazard to people and even structural damage to the house as water seeps through.

Regardless of whether the problem is a partial or complete clog, it needs to be fixed real quick before it gets out of hand.

If it is a complete clog, high chances are that the obstruction is close to the bowl. If it is visible from the bowl, you can remove it while putting some safety gloves on. If it is far you can use a toilet plunger to unclog the drainage pipes.

In case of a partial clog or if the plunger method doesn’t help for the complete clog, you can use an unclogging auger to effectively do the task. You can also improvise using a strong flexible wire most preferably with a hook at the end but take care not to scratch the bowl.

Flush in the end to confirm whether the problem is still there or not and if the water level doesn’t get to normal you should seek professional help.

 Another rare problem is the water level in the bowl staying lower than usual.

This might be caused by low pressure in the toilet drainage system due to poor plumbing thus creating a ‘sucking’ effect keeping the water level low.

The common cause of low bowl water levels is water level and flushing power problems in the tank.

Water Level Problems in the Toilet Tank

When the water level is higher than it should be in the cistern, it leads to unnecessarily high water usage consequently increasing your costs.

In some cases, the water might even start overflowing from the tank.

If there is no obstruction in the toilet’s drain or if the issue comes up on a regular basis, the water level in the toilet’s tank could be to blame for the extra water in the bowl.

Another issue is that the level of water remains low. A low-than-normal level of water diminishes the toilet’s flushing capacity. With a lesser flushing force, the toilet bowl will drain more slowly than previously.

The most typical cause of a low water level is a damaged or broken fill tube.When it is damaged, the water cuts off before the tank has had a chance to fill fully.

The issue could possibly be small, and all you need to do is make a few modifications to resolve the water level issue.

Many toilets allow you to change the water level. Raising or lowering the toilet’s float height affects the water level in the tank.

In a dual flush toilet, adjusting the water level is simple. The water flow is controlled by an integrated float assembly that rises and falls with the water level. The float is a ring-shaped device that goes around the toilet’s left-hand fill valve.

Depending on the valve, there are two methods for adjusting the level. One is a screw on top of the fill valve assembly. Tightening this screw counterclockwise reduces the water level, while loosening it allows the float to rise higher as the tank fills.

To adjust the water level the two sides of the lock that join the float valve to the fill valve assembly rail placed on the side can also be pressed together.

You may observe water filling the tank as you raise the water level in the dual flush toilet, but this is normal and should not be a cause for concern. It will turn off when the water level reaches its new level. Similarly, lowering the water level will not affect the situation until the following flush.

Flush the toilet and check the new level after you’ve done all of the necessary changes. If it is still not at the right level, make more changes. Flush as needed to check.

You may need to experiment with different water levels to ensure that the toilet bowl does not overflow, but that waste is effectively flushed down the drain.

 Some people prefer a lower water level in their tank since it saves them money and conserves water. However, if the water level in your toilet is too low, flushing may be hampered.


Unlike other types of toilets, dual toilets are more likely to clog, especially if they’re connected to a waste drainage system that is not designed especially for them, mostly those designed for traditional single flush toilets.

 This happens because most traditional flush toilets use a lot of water to flush waste thus they can work on drain pipes with a relatively small diameter effectively thus when you fix a dual flush toilet on such a drain, chances are that it will clog up fast or often.

 To prevent clogging, you should be cautious so as not to flush any foreign materials that can not dissolve in the wastewater or break down easily.

 To reduce the likelihood of someone flushing foreign goods, place a garbage bin in the restrooms, preferably near the toilet, and encourage everyone to dispose of foreign materials such as paper towels, diapers, cleaning & facial wipes, and feminine hygiene products in it.

You should also avoid flushing solid waste with the low volume option even if it appears to be effective in flushing everything from the bowl.

Another common source of clogging is flushing too much waste at once, which leads to drain pipe obstruction. As a result, it is recommended to flush the toilet twice to ensure that all waste is washed down the drain.

Incompatibility with the plumbing system can also lead to high chances of clogging as the previous drainage systems might have been installed designed to rely on large amounts of water and high velocity to drain out solid waste.

Thus, installing a dual flush toilet system on old drainage systems might lead to clogging as the small amount of water used to flush waste might not be effective in pushing the waste all along the drainage system pipes.

Dual Flush Button Dilemma

The flushing mechanism on many dual-flush toilets is operated by buttons rather than handle levers. The majority of them are located on the top of the cistern or toilet tank, which can be inconvenient for some people, especially children.

The high volume and low volume flush buttons are also not always clearly labeled on all models, which can be confusing to guests who aren’t used to using dual flush toilets. It’s possible that guests should be given a quick tour of the equipment.

Stiff buttons might be difficult to press for the elderly and individuals with disabilities. Buttons can also become stuck, forcing the toilet to run continuously leading to water wastage and increased costs.


You should expect to clean your dual-flush toilet more frequently than you did your basic toilets. The reason for this is that each flush leaves less water in the bowl. When choosing the low volume flush option on several models, some residue may remain in the bowl. Dual flush toilets, on the whole, necessitate more frequent cleaning..

The toilet might get stained and dirty thus becoming filthier far faster than standard-flush toilets. You’ll have to clean the bowl more frequently unless you choose a sophisticated self-cleaning dual flush toilet.

Other Dual Flush Toilet Cons/Disadvantages


The cost of dual-flush toilets is higher than the cost of other toilets. They are unquestionably more costly than a regular toilet. Purchase and installation costs are both more than for a normal toilet.

However, even when compared to other high-efficiency toilet designs, a dual-flush toilet is frequently more costly. Dual flush variants, on the other hand, are becoming more popular as a result of their efficacy and ability to save water. As a result, they’re getting more affordable thus accessible to the general population.


Dual flush toilet models that come with handles may confuse users who used to standard single flush toilets

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