How To Fix A Toilet That Randomly Runs: A Complete Guide

Likely the most used fixture in homes throughout the United States and throughout most of the world, toilets see quite a lot of use throughout the day. As a result, they frequently see a lot of wear and tear, but are appropriately built to last a very long time. 

Depending on the type of toilet and what it’s made of, there may come a time when you might need to replace or repair it. There are, in fact, a number of different potential issues that can pop up, beyond simple clogged pipes.

One such issue that can happen is that you find your toilet spontaneously running. Also referred to as a phantom flush, the sudden flushing of the toilet bowl often ends up with you gaining quite a high cost on your water bill if you don’t take care of it quickly. More often than not, people often ask themselves questions like, “how do you fix a toilet that runs randomly?”, as it can also interfere with daily life. 

Thankfully, the solution is quite easy to find if you know what caused it.

To help you find the answer to the question, “what does it mean when your toilet runs randomly and how to go about fixing it yourself?”, we’ve collected some of the most common causes. 

If you would rather avoid trying to fix the issue yourself, call our team at Clover Contracting for an estimate.

How do toilets work?

If you’ve ever got the chance to lift your toilet’s lid off to check what was happening, chances are that you might have gotten a little baffled by all the parts in there. Surprisingly, how it all works is far easier than it seems at first glance. With a simple lever system and a few sensors, your bathroom’s toilet easily gets rid of any lingering waste or nasty water before refilling again.

The process begins by flushing, the handle on the outside lifting the stopper like flapper at the bottom of the tank. The water that was in the toilet’s tank is released into the bowl and whatever that’s in there gets pushed down and into the piping via siphon jets. 

In the tank, the flapper drops back down and the toilet’s fill valve opens due to the decreased water. Through gravity and siphoning, the waste is pulled through into the drain system. From there, the fill valve draws in water from the connected supply line and the bowl is refilled again.

What makes a toilet run randomly?

There are a number of potential reasons that can cause your toilet to randomly run at some of the worst times. 

One of the most common reasons is that your home’s water supply has an excess of sediments or is too hard. Hard water minerals or sediments can cause a range of different problems inside the toilet tank, building up and potentially damaging parts inside it. Sometimes, though, this isn’t always the main issue, and you need to consider other causes.

The tank’s float might need to be lowered

In order to tell the toilet’s system to fill the tank with a certain amount of water, it has a small part called a float. This little part quite literally floats on top of the water in the tank, only lifting up a part inside the overflow tube when the tank needs to draw in water. When the float is too high, the toilet’s system draws in too much water, only for the overflow tube to drain it out.

If the float is the main cause of why the toilet keeps running, the part is typically stuck too high up for it to properly drop, forcing the overflowing water to continuously drain. The toilet can flush as usual, but it won’t solve the problem. Instead, all you’re left with is a continuously hissing toilet.

The toilet flapper may be cracked

When it comes to knowing the answer to the question, “how do you fix a toilet that runs randomly?”, the most common issue is that the flapper is degraded or cracked. 

Since the main purpose of the flapper is to only let a specific amount of water out before it drops and reseals the tank, a cracked one does the exact opposite. 

Though it may be a far slower “leak”, the water that leaves the tank via the flapper goes into the bowl, and too much of an overflow inside the bowl is likely to cause the entire toilet to flush despite no one pressing down on the handle.

The chain may caught or the wrong length

Another possible reason as to the problem of “my toilet randomly runs” is that there’s a problem with the toilet’s chain. This chain is what forms a sort of lever system, attached to both the lever or handle and the flapper to release the tank’s contents into the bowl. 

If the chain gets caught under the flapper or tangled on something, the flapper won’t seal properly and water will escape. This is the same problem if the chain is too long. On the other hand, if it’s too short, the flapper is more likely to dangle and won’t seal at all.

How to fix this problem yourself

Many of these issues can easily be solved quite easily once you know what the cause is. In the case of a cracked flapper, all you need to do is purchase and replace the flapper. 

If the chain is too long, too short or gets stuck, removing or adding a few links lets it be just long enough to not interfere with the flapper. And when it comes to the toilet’s float, you can loosen or even tighten the part’s arm to lower it.


People often ask why my toilet randomly runs, and there are a number of different causes as to why it does happen. Knowing the answer to the question, “how do you fix a toilet that runs randomly?”, can show that it can be quite simple to solve the potential causes yourself. 

However, if you find that none of these solutions fix the cycling issue, contact our team at Clover Contracting and we’ll be at your service.

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