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How to Fix a Running Toilet

Fixing a running toilet is a lot easier than you might think. In this article, we'll show you how to identify and solve the problem. Don't be intimidated by the plumbing. The fixes are straightforward, even if you don't have any plumbing experience. So stop wasting water and fix the toilet!

By the DIY experts of The Family Handyman Magazine

How to Fix a Running Toilet

Fixing a running toilet is a lot easier than you might think. In this article, we'll show you how to identify and solve the problem. Don't be intimidated by the plumbing. The fixes are straightforward, even if you don't have any plumbing experience. So stop wasting water and fix the toilet!

By the DIY experts of The Family Handyman Magazine

Stop a running toilet

The mysteries of a running toilet can drive you nuts. Whether you hear water running constantly or cycling on and off, we’ll help you decipher the clues so you can stop most leaks. Hardware stores and home centers carry the parts for almost every repair. One cause of a running toilet is a flapper that doesn't seal. If water from the tank seeps around the flapper and into the bowl, the flapper is probably shot. Test for a leaky flapper as shown in Photo 1.

To replace the flapper, first shut off the water supply valve under the toilet (or the main supply if the valve leaks!). Flush the toilet to drain out most of the water, and unhook the old flapper. Buy a new flapper of the same type and install it according to the instructions on the package. Hook the flapper chain onto the flush lever arm so there’s a little slack when the flapper is closed.

If the flapper doesn’t leak and the water still runs, inspect the fill tube connected to the overflow pipe (Photo 1).The end should be above the water line. If the end is under water, cut it back. Next, inspect the fill valve for visible signs of wear and test the float (Photo 2). If the float is improperly adjusted, the tank water level can rise above the overflow pipe and drain into it. Replace the old fill valve if it doesn’t completely shut off or it hampers the float-arm operation (Photo 3).

Install a new “floatcup”-style fill valve as shown in Photos 4 and 5. Adjust the float according to the package instructions to establish the proper water level. Finish the installation by attaching the flapper chain to the flush lever as described above. Turn on If the end is under water, cut it back. Next, inspect the fill valve for visible signs of wear and test the float (Photo 2). If the float is improperly adjusted, the tank water level can rise above the  overflow pipe and drain into it. Replace the old fill valve if it doesn’t completely shut off or it hampers the float-arm operation (Photo 3).

Install a new “floatcup”-style fill valve as shown in Photos 4 and 5. Adjust the float according to the package instructions to establish the proper water level. Finish the installation by attaching the flapper chain to the flush lever as described above. Turn on the water and test flush the toilet.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Hacksaw
    • Pliers

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Depending on your fix, you may need a new fill valve

Comments from DIY Community Members

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1 - 8 of 8 comments
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August 20, 10:08 PM [GMT -5]

I've looked at a couple of websites about this little problem and I'm amazed that no one is doing the diagnostic this way:
1. Turn of the water at the valve below the toilet
2. Flush the toilet so the empty (well, almost empty)
3. Pour in a quart of water from the sink using some kind of container
4. Now observe if you have any water running into the bowl
5. If you do, then the problem has nothing to do with the float, the float valve, etc.
This makes me sound like an expert, but I still haven't solved my toilet problem. It runs with only a quart of water poured in it, and I've replaced the flapper. Doesn't help. So what's up?

May 13, 12:02 AM [GMT -5]

It sound like running water but it is air. I live on the first floor of an apartment building and I changed out the fill valve it made no difference. Even when I turn off the water it still runs, if I drain the tank then it stops. why, it is air bubbles?

March 19, 5:49 PM [GMT -5]

The flapper is fine. If I remove the fill tube from the overflow, water flows from it, fills the tank, it shuts off, does not leak. I can flush the toilet.

If I do not remove it, water goes into the bowl, and water keeps running into the overflow tube but it never fills the tank, it just keeps running.

I cannot figure it out.

July 31, 8:23 PM [GMT -5]

Still a mistery... if I empty all water inside the tank and shut off the water supply, I still can see running water on the bowl. The water level is below the flapper and leaking continues.. Should it be the wax ring??

September 23, 9:56 AM [GMT -5]

what does "check the fill tube length and cut it back" mean??? How do I check the length? And what am I trying to see? And how would I "cut it back?" You assume too much background knowledge!

August 17, 5:19 PM [GMT -5]

The fill valve shown in the picture has a nob on the cap that adjusts the water level without having to bend the float rod. The overflow tube tht is being cut with a hacksaw should be set below the tank handle level or above the waterline marked on the toilet tank. The setting on the fill valve can be misleading since the fill valve has an adjustable height. Older toilets with brass flush valves can be nearly impossible to get to stop dripping because the brass seats get etched over time and even emory cloth wont polish them smooth. Some plastic flush valves are very particular as to which type of flapper will seastr properly. Most important of all if you are using a flapper that has one of those round rings attached to it and your flush valve has little tabs to hook the flapper on, you MUST cut the round ring off.

August 06, 4:52 PM [GMT -5]

I have done this and it still runs. Does anyone have anymore ideas or hints on how to fix it besides having to keep turning the water valve off? Thanks

June 03, 12:07 AM [GMT -5]

This is a great way to save $$ on your water bill and it's pretty easy to do.

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