Yes. A leaky toilet can be something besides the flapper, and where the water shows up tells you the part. Water into the bowl points to the flapper or fill valve. Water under the tank means the tank gasket or bolts. Water at the supply line means a worn connection. Water at the base means the wax ring or flange.
Where is the water showing up?
Start by drying everything. Wipe the tank, the supply line, the wall valve and the base with a paper towel, then watch where the first bead of water returns. That spot points you to the part.
| What you see | Most likely part | Do it yourself? |
|---|---|---|
| Toilet refills on its own, or tank color shows in the bowl | Flapper | Yes |
| Water keeps running into the overflow tube, or a hiss after the tank is full | Fill valve | Usually |
| Water dripping under the tank where it meets the bowl | Tank-to-bowl gasket or tank bolts | Usually |
| Damp spot or drip at the wall valve or supply line | Supply line or its connections | Yes |
| Water pooling around the base of the toilet | Wax ring or closet flange | Sometimes, but it's messy |
| Water coming from a crack in the tank or bowl | Cracked porcelain | No, replace the toilet |
One caution on that last row. Cracks can be hairline and hard to see, especially inside the tank. If you can't find any other cause, look closely at the porcelain, and feel along the inside of the tank with a dry paper towel.
How do you rule the flapper in or out?
Do the dye test first, because it takes two minutes and settles the most common cause. Add a few drops of food coloring to the tank and wait without flushing. If color shows up in the bowl, the flapper is leaking. If the bowl stays clear, the flapper is fine and the leak is somewhere else.
The EPA recommends the dye test, and it says "an old or worn flapper can cause your toilet to flush on its own or silently leak thousands of gallons a year." A toilet can waste water all day without a sound or a puddle. The same EPA page puts the average household leak at over 9,300 gallons a year, and toilets are one of the first places it tells you to look. It also says to replace a damaged flapper at least every five years. Our step-by-step for the swap is in how to replace a toilet flapper and fill valve.
What if the dye still shows up with a brand-new flapper? The flapper isn't the only thing it seals against. Check these four, in this order:
- 1The flush valve seat. The flapper seals against the rim of the flush valve, and a rough rim leaks past even a new rubber flapper. Fluidmaster says to "check the flush valve seat for corrosion or unevenness" by moving your finger around the rim to feel for nicks. Mineral crust can be wiped off, but a pitted seat needs a repair kit or a new flush valve.
- 2The chain. A chain that's too short holds the flapper open a crack, and one that's too long can slip under it. Fluidmaster's guidance is 1/4 to 1/2 inch of slack, and to cut excess chain that interferes with the flapper seating.
- 3The flapper fit. If the back half of the flapper leaves a gap against the seat, it isn't sitting square. Fluidmaster recommends swapping it for a flexible-frame style. Take the old flapper to the store and match the size to your flush valve.
- 4The water level. If the tank fills past the top of the overflow tube, water spills down it and the fill valve keeps cycling. Lower the float or adjust the fill valve so the water stops about an inch below the tube. Fluidmaster also puts the overflow tube at least one inch below the tank lever hole, so water can't leak out around the handle.
Those four fix most "new flapper, same leak" cases before you need to look at anything else.
If the flapper checks out, you can move on to the rest of the list with a clear head.
What causes leaks at the fill valve, the tank, and the supply line?
The fill valve. Fill valve leaks are easy to miss because the water often runs into the overflow tube and out of sight. A fill valve that won't shut off keeps sending water into the overflow tube. Listen for a hiss or trickle after the tank should be full. Oatey lists a bad fill valve connection or gasket as the cause when water shows up beneath the tank, and it says to hand-tighten the nut and not overtighten. Check that the float moves freely so the water shuts off when the tank is full. A stuck float is a small fix. Our page on how to fix a running toilet walks through both.
The tank-to-bowl gasket and bolts. Two things live between the tank and the bowl: a gasket and the bolts that hold the tank on. Oatey lists loose bolts among the main causes of toilet leaks, and it says to check the bolt rubber washers and bolts for cracks or corrosion. The rubber gasket can also wear and fail. Oatey's fix is to drain the tank, remove the bolts, lift off the tank, replace the gasket and any worn washers, reinstall the tank, and hand-tighten the bolts, alternating sides. If the leak only shows after a flush and it drips from where the tank meets the bowl, this is the likely cause.
The supply line. The braided line from the wall valve to the toilet can loosen or wear. Oatey suggests replacing it every three to five years. Turn off the water at the wall valve, disconnect the old line at both ends, and hand-tighten a new one. Wipe the connections dry, then check them again in an hour. If the wall valve itself drips, that's a separate repair, and it's a good reason to have a plumber look at the valve.
When is it the wax ring or the flange?
Water on the floor around the base points to the wax ring or the closet flange, the fitting the toilet sits on. Oatey says water pooling around the toilet base usually points to a wax ring or flange failure.
That's the one to act on quickly. A slow seep at the base can soak a subfloor for weeks before you see damage. Our page on why a toilet leaks at the base has the signs and the steps, and fixing a broken toilet flange covers the case where the flange itself is cracked. Oatey rates the wax ring and flange repair as an expert job and suggests calling a plumber, and that's fair. Pulling a toilet and resetting it takes some know-how to get the compression right.
How do you know the fix worked? Don't trust a dry floor after ten minutes. Once you've made a repair, dry every joint and the base, flush a few times, and press a fresh piece of toilet paper against each connection: the tank bolts, the supply line, the wall valve and the base. Paper shows a slow bead of water that your eye misses. Then repeat the dye test in the tank, and check again the next morning before the first flush. A toilet that's silent and dry after a night is fixed. If you can't say for sure, keep a dry paper towel under the tank overnight and look at it in the morning.
If you replaced a flapper, a supply line or a fill valve and you're still seeing water, go back to the table at the top. It's easy to fix the wrong part first. The EPA says toilet leaks are often silent, so give it the paper-towel and dye tests rather than your ears alone.
What if none of that fits, or you can't stop the water?
Sometimes the leak isn't a leak at all. A tank can sweat and drip water down the outside on a humid day, which looks like a leak but isn't. If the dye test is clear and the drips come from the outside of the tank, look at the pattern and the weather before you take anything apart.
If you've worked through the list and the water is still showing up, a plumber can trace it. HQ gives free estimates and upfront pricing, and we offer 24/7 emergency service if water is on the floor and you can't stop it. Meanwhile, close the wall valve behind the toilet, and that stops the water. That's the fix for tonight.
A leak that makes the fill valve cycle by itself is explained in why a toilet flushes on its own.