The short answer
The flapper is the rubber seal at the bottom of the toilet tank. In a Northern Virginia home, a toilet that runs on its own, refills by itself every so often, or needs the handle jiggled usually has a worn flapper or a chain that’s the wrong length. The part costs a few dollars and the swap takes about 15 minutes. Get the size right, 2 inch or 3 inch, give the chain a little slack, and keep cleaner tablets out of the tank so the new one lasts.
Test it in ten minutes
- Take the lid off the tank and set it somewhere flat. It’s heavy and it breaks.
- Look at the water level. If water is spilling into the open top of the overflow tube, the tall tube in the middle, that’s the fill valve, not the flapper.
- Put a few drops of food coloring in the tank. Don’t flush.
- Wait ten minutes, then look in the bowl. Any color in the bowl means tank water is getting past the flapper.
- Flush to clear the color so it doesn’t stain the bowl.
If the water is going down the overflow tube instead, the toilet fill valve is the part to look at. If the tank is losing water and the bowl stays clear, the water is leaving another way, often to the floor, and toilet tank leaking goes through the bolts and the gasket.
Swipe to see all columns →
| What it’s doing | Usually | The fix |
|---|---|---|
| Color shows in the bowl after ten minutes | A worn flapper, or a rough seat under it | A new flapper; a seat kit if the rim it sits on is pitted |
| Refills for a few seconds every so often | A slow leak past the flapper | A new flapper |
| Runs until you jiggle the handle | Chain too short or tangled, so the flapper can’t drop | Give the chain a little slack |
| Flushes weak, tank only half empties | Chain too long, flapper drops early | Take up the slack |
| Water runs into the overflow tube | Fill valve set too high or worn | Adjust or replace the fill valve |
A toilet that refills by itself for a few seconds at a time has a name, a phantom flush, and toilet refilling by itself walks through it with a second test.
2 inch or 3 inch
Look at the round opening the flapper covers at the bottom of the tank. Most toilets made before about 2005 have a 2 inch opening. Many newer ones have a 3 inch opening, which lets the tank empty faster with less water. Measure across it, or find the model number stamped inside the tank, usually on the back wall near the water line, and match the flapper to it.
Two more things on the box matter. Some toilets don’t use a round flapper at all. They have a tall canister or a flat seal made for that one model, and the replacement comes from that maker. And on low flow toilets, the flapper is tuned to how much water the toilet uses. A universal flapper can make a 1.6 gallon toilet use more, or flush weak. If the old one had a dial or a float on it, buy one with the same setting.
Put the new one in so it seals
- Turn the valve behind the toilet clockwise until it stops, then flush to empty the tank.
- Unhook the chain from the handle arm and slide the old flapper off the two pegs on the overflow tube.
- Wipe the rim it sat on with a scrub pad and run a finger around it. Slime and mineral wipe off. A rim that’s pitted or cracked won’t seal under any flapper.
- Slide the new flapper onto the pegs and let it drop. It should sit flat and centered.
- Hook the chain so there’s about half an inch of slack with the flapper closed. Clip off extra chain so it can’t fall under the flapper.
- Open the valve, let the tank fill, flush a few times, then run the dye test again.
Why flappers wear out
Rubber hardens and warps with time. Most flappers last a few years. Cleaner tablets that sit in the tank, the blue ones and the bleach ones, speed that up a lot, and several toilet makers say not to use them. Mineral in the water builds up on the rim the flapper sits on and leaves a gap. A flapper that feels stiff, slimy or leaves black on your fingers is done.
When it isn’t the flapper
A brand new flapper that still lets color through means the rim under it is rough, or the overflow tube is cracked under the water line. Both are fixed by replacing the flush valve, which means taking the tank off the bowl and new tank bolts and a gasket. That’s worth doing once rather than twice. If the toilet hisses, whistles or bangs, what each toilet noise means matches the sound to the part.
What a leaking flapper costs
The EPA says a worn flapper alone can waste thousands of gallons a year. Water and sewer here are billed every three months, so you see it as a jump on a bill long after it started. How much a running toilet adds to the water bill works out the numbers.
A leaking flapper is one of the quiet warning signs. Every warning sign around the house, from a furnace’s blinking light to the sounds a house makes, is in one guide.
Fix it small, fix it now
A toilet problem caught early stays cheap three ways. The water and sewer bill stops climbing. The water stays out of the floor and the ceiling under it. And it stays a part and an hour instead of a subfloor later. Almost everything we find wrong inside a toilet is repairable, and once it’s fixed right, you stop listening for it.
What it costs when we fix it
Flappers, fill valves, handles, shutoff valves and supply lines are all toilet repair, $250 to $900, with the price in writing before we start, and we check the rest of the toilet while the lid is off. When the toilet itself is worn out, a new one installed runs $800 to $1,300, and this month’s coupons on our offers page take $100 off a new toilet, or $50 off any plumbing repair over $400. Any plumbing repair also comes with a whole-house plumbing inspection, a $149 value. If water is showing up where it shouldn’t and you can’t tell where it starts, leak detection runs $200 to $500. A plumbing diagnosis visit is $49, or $250 after hours.
Call (703) 997-9757, day or night, or book a toilet repair online. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
How do I know if my toilet flapper is bad?
Put food coloring in the tank and wait ten minutes without flushing. Color in the bowl means water is getting past the flapper. A toilet that runs on its own or refills every so often points the same way.
How long does a toilet flapper last?
A few years in most homes. Cleaner tablets in the tank and hard water wear them out sooner.
Are toilet flappers universal?
No. They come in 2 inch and 3 inch, some toilets use a canister or a seal made for that model, and low flow toilets need one tuned to their flush. Match the model number inside the tank.
Why does my new flapper still leak?
The chain is too tight, the flapper isn’t sitting centered, or the rim it seals against is pitted. A pitted rim means a new flush valve.
How much does it cost to replace a toilet flapper?
The part is a few dollars. When we do it, a flapper is a toilet repair, $250 to $900, priced in writing before we start, and we check the fill valve and the seat while the lid is off.
