How to Fix a Toilet That Randomly Runs

Does your toilet seem to have a mind of its own? Random flushes that happen when no one is using the toilet are a result of "phantom flushing." It's not ghostly spirits messing with your toilet, but it does mean something isn't quite right with your toilet's inner workings. To stop wasting water and to stop the annoying sounds, troubleshoot your toilet to determine if you need to adjust the fill valve or replace a part.

Phantom flushing sounds like spontaneous flushing at random times, but it's actually a refill rather than a flush. It happens because the toilet tank is losing water, and the toilet refills it when it gets low. A common offender is your toilet flapper, which can slowly let water trickle into the bowl if it doesn't seal tightly. Your tank can also lose water if there's an issue with the fill valve. Many of the issues that cause phantom flushing involve simple replacement parts that are relatively easy to install yourself.

An easy way to determine if your toilet flapper is leaking is to squeeze a few drops of a dark-colored food dye into the water of your toilet tank. Don't use or flush the toilet. Check back in about 15 minutes to look for traces of the food dye in the toilet bowl. If you spot the coloring in the bowl, it's your confirmation that the flapper is bad and needs to be replaced.

If you determine your toilet is leaking, replacing the toilet flapper can help you remedy the issue. A replacement flapper is inexpensive and easy to install. Check your current flapper to ensure you get the same size and type of flapper as a replacement, which helps you get a tight seal. You can take your old flapper to the hardware store to get help finding a suitable replacement if you're unsure of what to buy.

To remove the old flapper, shut off the water to the toilet using the shutoff valve below the tank. Flush the toilet to empty the tank as much as possible. With the water supply shut off, it won't refill after you flush it. Taking a picture of the inner workings makes it easier to put the new flapper in place correctly.

Disconnect the flapper chain from the flush lever and pull the flapper off the pegs. Wipe the area where the flapper sits so your new flapper can seal tightly. Slide the new flapper onto the pegs. Connect the chain to the flush lever. Turn the water back on and test the flapper.

If the flapper isn't the issue, the fill valve is the other likely culprit. The tube in your toilet tank is the overflow tube. If the float is adjusted properly, the water level should stop about 1 inch below the top of that tube. You can adjust the float if the water level isn't correct. The adjustment method depends on the type of fill valve you have.

Some models use an adjustment screw to change the water level. Others have a clip that you pinch to release and slide. You might need to test different positioning to get the correct water level.

If adjusting the float doesn't fix the issue, replacing the fill valve or the refill tube might be necessary. To replace it, you'll need to shut off the water supply and drain the tank. The valve extends out the bottom of the tank to connect to the supply line, and a lock nut holds it in place. You'll disconnect the supply line to remove the old fill valve. Then, install the new fill valve, turn the water back on, and test the new fill valve.