Dual Flush Toilet Troubleshooting Guide (7 Issues Fixed!)

The dual-flush toilets’ water conservation capabilities which in turn lower your water bills, is their most significant selling point and why many homeowners install them. However, just like other toilets, these have their own set of issues that necessitate knowledge of dual-flush toilet troubleshooting.

The most typical dual flush toilet problems include water continually running, clogging and leaks, fill valve problems, and water level problems in the toilet bowl or the tank. Moreover, plumbing compatibility issues should also raise your eyebrows.

With a dual-flush toilet troubleshooting guide, you can rest assured that you can handle issues that may arise confidently. So, keep reading for comprehensive steps on how to handle dual-flush toilet problems.

Dual flush toilet not flushing completely

Dual Flush Toilet Troubleshooting (Problems & Fixes)

In a hurry? here is a summary of most likely dual flush problems, their probable causes and suggested fixes.

 ProblemPossible CauseQuick Fix
1.Dual flush toilet keeps runningA misaligned or worn-out flapper or sealA broken zip tiePresence of foreign elements in the toilet tank  Replace the defective flapper or seal. Replace the broken zip tie and remove debris in your toilet tank.  
2.CloggingInstalling toilets on sewage systems not suited for themAccumulation of human waste and tissue paperConsult professionals before installing dual-flush toilets. Avoid flushing foreign materials down the toilet drain
3.Fill valve problemsA broken Cistern valveClear anything blocking the seal
4.Dual flush won’t flush properlyLow water level in the tankClogged drainage systemOld and faulty flapper.Check the water level in the tank Replace faulty flapper
5.Incompatibility with plumbingOld plumbing mechanismsConsider getting a different toilet
6.Maintenance and cleaning problemsFailing to clean regularlyMaintain a regular cleaning and maintenance routine
7Water level issuesClogs or loose screwClear clogging. Turn the screw counterclockwise or clockwise to lower and raise the water level, respectively

1. Dual Flush Toilet Keeps Running

One prevalent problem to look out for in dual-flush toilets is water running continually into the bowl. You will notice this after determining how long it takes to fill your tank after flushing, but water keeps dripping into the toilet bowl.

It signifies that the mechanism lets water flow past the flush valve flapper or that water from the tank is entering the overflow tube. Failure to detect this early enough could skyrocket your water bills.

To troubleshoot the fault, check out the following:

a) A Misaligned or Worn-Out Flapper or Seal

A skewed and worn-out flapper and zeal can cause leaking and water to run continually into the bowl even after filling the tank. This silicone or rubber component may deteriorate with time, becoming porous.

Additionally, you may have misaligned the flapper, causing water to seep through.


  • Consider replacing the worn-out flapper and seal.
  • Try re-aligning the flapper or seal.

b) A Broken Zip Tie

Dual flush toilets usually have fill valves with zip ties to hold the valve base. Unfortunately, you can expect the zip tie to wear out and break after many days of service, causing water to flow into your toilet bowl continuously.


You can add a second zip tie or replace it to curb the leaks.

c) Foreign Elements in the Toilet Tank

In some situations, foreign materials, such as pieces of broken materials, debris, and dust, can find their way into your toilet tank and inhibit the normal functioning of the flapper and valves.


  • Stop the water supply to your toilet and lift the fill valve cover. Look for debris and remove it.
  • You can use a small brush to clean the valve. After that, restore the water supply and check for leaks.
  • If foreign elements were the genesis of the problem, this procedure should fix it.

2. Dual Flush Toilet Clogging

Clogging is a somewhat inevitable and common phenomenon, especially with dual flush toilets built on a sewage system not ideal for them. It’s also a prevalent issue with siphon flush toilets fitted in seldom-used restrooms.

Remember, dual flush toilets function better in regularly used restrooms because constant flushing limits waste material buildup inside the drain pipe.


Minimize flushing foreign materials down your toilet drain apart from human waste and toilet paper since these models weren’t designed to flush cotton swabs, menstruation products, diapers, and dental floss. Also, include a small label on each button to eliminate confusion about which button to press after using the toilet.

Additionally, full-flush the toilet twice to give the waste you flushed enough momentum to get to the street sewage and thus prevent clogging.

Are dual flush toilets hard to repair?

3. Dual Flush Toilet Fill Valve Problems

A Cistern fill valve is an essential part of this toilet model, meaning any fault with it could result in the continual running of water in the toilet bowl. A defective fill valve won’t efficiently monitor the water level required to cut off the water supply.

Any remaining water goes down the tube that connects to the toilet bowl. Consequently, it would trigger an unending trickle of water into your tank and result in massive water wastage.

If you just installed a new valve but observe that water is still trickling into your bowl, it is conceivable that debris could be obstructing the component. Apart from that, look out for rust and scale buildup in the toilet tank, which might appear little at first but end up causing significant damage with time.


Always make sure the water supply is working, and change the flushing system regularly. Additionally, clear anything in the way of the seal, and watch out for too much water in the tank.

4. Problems with Water Levels in the Tank

A higher water level in the cistern than the recommended one will cause excessive water use, culminating in astronomical water bills. In certain situations, the tank may overflow, and if this problem recurs in the absence of clogging, the higher-than-recommended water level in the tank is the cause.

Apart from that, you could also face a lower-than-usual water level in the toilet tank that impairs the toilet’s flushing efficiency. It would cause the bowl to drain slower than before.

A broken or damaged fill tube is the chief cause of low water levels in the toilet. It cuts off the water supply before the tank fills.


  • Tightening the screw atop the fill valve anticlockwise lowers the water level, while turning it clockwise will raise the float while filling the tank.
  • Squeeze the two sides of the lock connecting the fill valve and the float valve to change the water level.

NOTE: Raising the water level in your dual flush toilet will probably cause water to fill the tank. As soon as the water reaches its new level, it will shut off. Likewise, reducing the water level does not affect the condition until the next flush.

5. Incompatibility with Plumbing

Plumbing networks in modern homes normally work with low-flush toilets, unlike in older homes. Since the plumbing in older homes was designed for high-flush toilets, fitting a dual-flush type may cause compatibility concerns.

Old plumbing mechanisms might dip or have other issues hindering the toilet from performing efficiently. Furthermore, the older the pipe network, the greater its probability of influencing the operation of your toilet.


Before getting a dual flush toilet, ensure your plumbing system can handle and is compatible. Alternatively, consult a reliable plumber or a professional to evaluate your plumbing system and determine whether you can install a dual-flush toilet in your newly acquired apartment.

Why is my dual flush toilet not flushing properly?

6. Dual Flush Toilet Won’t Flush Properly

The sight of waste in the toilet is annoying, and it is worse when your dual flush fails to flush properly. It could stem from problems with the flush mechanism, for instance, a disconnect between the flush valve chain and the flush ball or the flush lever.

Here are causes and fixes.

a) Low Water Level in The Tank

The bowl won’t receive enough water to flush the waste when you have a low water level in the tank.


Adjust the float after ascertaining the water level in the tank is below the required level.

b) Blockage In the Toilet Drainage System

Your toilet won’t flush properly if there is a blockage in the drainage system.


Unclog your toilet to restore proper flushing and drainage. If this doesn’t work, seek professional help.

c) An Old or Faulty Flapper

An old or broken flapper causes water to seep out of the toilet tank. Failure to adjust the chain to the right length would also cause improper flushing since it reduces the amount of water meant for flushing.


Check your flapper chain and ensure it has about ½ inch of slack, ensuring it is not too tight or loose, and well adjusted. Additionally, check whether you have an old or defective flapper and replace them.

7. Problems with Cleaning and Maintenance

Many homeowners rush for dual-flush toilets because of their ability to use less water. However, this could be a drawback when it comes to cleaning and maintenance because these models reserve little water in their tanks, potentially causing dirt and bacteria buildup.


Clean your toilet regularly, and use a toilet brush to scrape the bowl.

Final Thoughts on Dual Flush Toilet Troubleshooting

Dual flush toilets come in handy in water conservation and keeping water bills in check. However, understanding their problems would help you make an informed purchase.

If the problems persist, seek professional help.

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