Problems With Dual Flush Toilets

Installing a dual flush toilet in your home is an excellent way to conserve water and a great step towards being more environmentally friendly. By giving you the option for a full or half flush, dual flush models can significantly reduce toilet water consumption by 60 to 80%, without sacrificing on performance.

However, any toilet has its issues that prevent it from functioning as it should and dual flush models are no different. Knowing the potential problems of these toilets can be useful and save you money since you won’t need to keep hiring professional plumbers every time something crops up.

If your dual flush toilet hasn’t been functioning the way it should and you’re not sure what could be wrong, we’re here to help. In this article, we’ll be covering some of the most common issues of dual flush toilets and what you can do about them.

But first, here’s a brief look at how dual flush toilets work.

How Dual Flush Toilets Work

Flushing toilet

Dual flush toilets use two buttons to flush different amounts of water according to your needs. These are push-button toilets that depend on gravity to remove waste from the bowl.

The toilet comes with two buttons on the cistern, one delivering 3 liters of water for liquid waste and the other one delivering 6 liters for solid waste.

Dual flush toilets have a larger 10cm trapway to make it easier for waste to be flushed out. They’re excellent at saving water, as they retain only a little water in the bowl at any given time compared to traditional toilets.

Installing a dual flush toilet is an excellent way to save water, but if this isn’t an option, there are other water-saving devices for standard toilets. However, while dual-flush toilets have many benefits, there are some common issues that are associated with them. Here’s a look at the most common problems of dual flush toilets.

Running Water

One of the most common problems with dual flush toilets is water running into the toilet bowl even after the tank is supposed to be completely full. A lot of water can get wasted this way if you don’t notice that it’s leaking. If this keeps happening, check to see if any of the following issues could be the cause.

Dual flush toilet tank

Inside a dual flush toilet tank

  1. The flapper or seal could be misaligned or worn out: check for any cracks in the flapper or seal because this could cause the leaking. If so, this component needs to be replaced. If the problem is misalignment, see if you can re-align the flapper or seal to stay in place without moving about.
  2. The Zip Tie could be broken: most dual flush toilets have a fill valve with a zip tie. This is included to keep the base of the valve set in one place. Expect the zip tie to wear down and break over time. But when this happens, the result would be water running continuously into the toilet bowl. In this case, the zip tie can be replaced, or you can add a second one to stop the constant leaking.
  3. Debris: in some cases, the water may not be as clean as you think it is or dirt and dust can enter into the toilet, resulting in malfunctioning of the fill valve. If you suspect this to be the problem, turn off the water supply to the toilet and remove the fill valve lid. Check for any debris and if any, make sure to remove all of it. To make the job even more thorough, use a small brush to brush out the valve. Once the valve is well cleaned, turn on the water supply and check to see if it works. If debris was the issue, the problem should be solved.


Dual toilets, especially those that are installed on a sewage system that wasn’t designed for them, tend to clog more often. This is a common problem with siphon flush toilets (the toilets that come with a lever on the side of the tank) installed in bathrooms that aren’t used much. Wash-down flush toilets (those that use a push-button flush) need to be cleaned more but don’t clog up as often. 

Dual flush toilets work best when installed in bathrooms that are used frequently since regular flushing prevents building up of waste material inside the drain pipe. Here are some ways you can prevent your toilet from clogging up too often.

  1. Be careful about what you flush: don’t flush anything that doesn’t come from your own body and isn’t toilet paper. The toilet isn’t made to dispose of things like diapers, feminine hygiene products, cotton swabs or dental floss so dump these in a trash can and use the toilet the way it’s meant to be used.
  2. Try double flushes: for bigger jobs, try flushing the toilet twice. Most toilet clogs occur due to excess toilet paper so if you’re using a lot of it, try flushing half of it at a time. This will help to minimize the chances of clogging your toilet.

Cleaning and Maintenance

As we mentioned before, dual flush toilet models need to be cleaned a lot more than standard single flush toilets. This is because dual flush models hold less water in the bowl which can result in accumulation of dirt.

To prevent the dirt from building up, clean the toilet regularly. Use a powerful toilet bowl cleaning solution and apply it on every corner of the toilet that you can reach, scrubbing both the inside and the outside as well. You might also want to try pouring distilled vinegar in the flush tank water and letting it dissolve. Then, flush several times to remove the vinegar and clean out the bowl.

It’s important to make sure that the water holes along the rims of the toilet don’t clog up as this can impair its function and increase the dirtiness, so brush well to keep them clean and unclogged. Aim to clean your toilet bowl every day if possible to keep it sparkling and prevent any bad odors.

Incompatibility with the Plumbing

Plumbing systems of newer residential construction are made to be compatible with low-flush toilets but with older homes, however, this isn’t the case. In older homes, the plumbing systems were made for high-flush toilets, so when installing a dual flush model, there can be issues with the compatibility.

Old plumbing systems can begin to sag, dip or have other problems that may prevent your toilet from working as it should and the older your plumbing system is, the more it could affect the performance of your toilet.

If you’re worried about the compatibility of your plumbing system with a dual flush toilet, talk to a professional before you go ahead and choose a toilet for your home.

The Cost

Dual flush toilets are more expensive than single flush models. You can expect the cost of one of these to start from around $175 whereas a single flush model would typically cost less than $100. However, the demand for dual flush models is increasing due to their effectiveness and water conservation abilities. As a result, they’re becoming increasingly affordable to the public.

Although the initial cost of installing a dual flush toilet can be rather high, you’ll be saving a large amount of water in the long run which means that you’re likely to see a significant difference in your water bills. These toilets also comply with federal water regulations and are typically WaterSense certified.

The Bottom Line

So there you have it: the most common problems that you’re likely to experience with a dual flush toilet.

Most of these issues are unlikely to occur in a brand new toilet. However, with time they may emerge depending on how much you flush it and how well you maintain it and keep it serviced.

Every toilet has its issues sooner or later but being informed about them and how to deal with them will help you in the long run.

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