Toilet Running Periodically and Randomly? A Minnesota Plumber Explains

If your toilet runs on and off when not in use, you’re probably pretty annoyed and ready to figure out what’s wrong with your toilet. So what’s causing this?

A toilet that runs for a while and then stops most likely has a bad “flapper”, the rubber seal that stops water from flowing from your toilet tank to the bowl.

The #1 reason we see flappers in the MN area “go bad” is because of hard water, i.e. water that has high mineral content. Toilet flappers usually last several years but wear out much faster in hard water.

A worn out or damaged flapper will allow water from your tank to slowly and randomly leak into your bowl even if it’s not being used.

The solution? Replace the flapper. (Don’t worry, we’ll show you step-by-step how to do this.)

But before you roll up your sleeves and dive in, let’s take a closer look at how your toilet should work. (Trust us, this quick tutorial will make your DIY toilet fix much easier...and cleaner.)

How your toilet (should) work

When your toilet is flushed, several steps must happen in order for the bowl to empty and refill for the next use:

Step 1: When the handle is pulled, prompting the “flush”, it pulls up on a chain connected to the flapper.

Step 2: The flapper lifts and releases water into your toilet bowl

Step 3: When the tank is completely drained of water, the flapper closes and makes a tight seal.

Step 4: Water from your home’s water line enters the tank from a connected valve to ready the tank for the next use.

How your toilet is actually working (with a bad flapper)

If you have a bad flapper, it’s unable to form a tight seal.

When that happens, water from the tank will slowly leak out whether or not the toilet is flushed. The water draining from the tank to the bowl is the “running” noise that you hear. 

If enough water enters the bowl, the toilet may even flush on its own at random times.

So what causes a flapper to go bad? Over time the rubber flapper can accumulate sediment buildup, warp, break or harden.

If any of the above sound like your flapper, let’s get you on your way to the next step: replacing it.

How to replace the flapper

What you’ll need:

Step 1: Remove the top of your toilet tank (you won’t even need to cut off your water for this). Locate your old flapper and lift the chain to drain the tank of water. 

Note: this will prompt your fill valve to begin filling the tank with water but as long as the flapper is not in place, the water will not fill up and get in your way.

Step 2: Disconnect the old flapper chain from the flush lever. Then, remove the old flapper by pulling the sides off of the “ears” of the overflow tube or by using your pliers to pop them off. Throw away the old flapper.

Step 3: Connect your new flapper valve to the ears on the overflow tube. They should snap in place. Make sure the flapper positions naturally directly over the drain.

Step 4: Clip the new chain to the flush lever. Be careful here because the measurement of the chain needs to be precise. If it’s too long, the excess can get stuck under the flapper and prevent it from sealing properly. If it’s too short, it won’t allow the flapper to reposition over the drain properly.

Make sure that there is some slack in the chain (but not too much). 

Then, fiddle with the handle to make sure that the range of motion on the chain allows the flapper to open and close back down directly over the drain.

Use your needle-nose pliers to cut any excess chain length.

Need help from a Minnesota plumber?

Don’t feel like dealing with the hassle of replacing your own toilet flapper?

No worries.

Just schedule your appointment with On Time Service Pros, and we’ll send over a reliable MN plumber in no time.


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