Toilet Tank Repair: How to Fix the Common Problems

Before you start

Shut the water off and empty the tank before you reach in. Every repair below starts this way.

Take a photo of the inside of the tank before you take anything apart. It shows where the chain hooks on and how the refill tube was routed.

Which tank part needs fixing

Match the symptom to the part. Oatey, a maker of toilet seals, sorts tank leaks the same way.⁠[4]

1. 01

   Worn or warped flapper

   Most commonDIYTime: 20 min

   Water trickles into the bowl and the fill valve turns on by itself.
   Fix it: Worn or warped flapper →
2. 02

   Fill valve clogged or worn out

   CommonDIYTime: 15–45 min

   The tank fills slowly, hisses or never shuts off.
   Fix it: Fill valve clogged or worn out →
3. 03

   Water level set wrong

   CommonDIYTime: 10 min

   Too high runs into the overflow; too low gives a weak flush.
   Fix it: Water level set wrong →
4. 04

   Loose handle or wrong chain length

   CommonDIYTime: 10 min

   You have to jiggle or hold the handle.
   Fix it: Loose handle or wrong chain length →
5. 05

   Leaking tank-to-bowl gasket or bolts

   Less commonDIY with careTime: 1–2 hr

   Drips from the tank bolts or the joint under the tank.
   Fix it: Leaking tank-to-bowl gasket or bolts →

Water spreading from under the toilet base, not the tank, is a different job. See toilet leaking at the base.

Replace the flapper

Korky says well water, hard water, treated city water and in-tank cleaning tablets all wear down a rubber flapper until it stops sealing.⁠[6] Fargo's water department says most toilet leaks come from a faulty flapper and suggests replacing it every 3 to 5 years.⁠[5]

1. 01

   Step 01 of 06

   Find the right size

   • Time: 5 min

   Korky calls this the most important step, because some flush valves need a specific fit.⁠[6] Fluidmaster sells separate flappers for 2-inch and 3-inch flush valves, so check the size of yours.⁠[7]

   You'll know it worked when: You have a flapper that fits your flush valve.

2. 02

   Step 02 of 06

   Mark the level and drain the tank

   • Time: 3 min

   Close the water, flush normally and mark where the level drops. Then hold the handle down to drain the rest.⁠[6]

   You'll know it worked when: A pencil mark shows where the water fell to on a normal flush, and the tank is empty.

3. 03

   Step 03 of 06

   Unhook the old flapper

   • Time: 2 min

   Unhook both flapper ears from the arms on the flush valve, then unhook the chain from the lever arm.⁠[6]

   You'll know it worked when: The old flapper and its chain are out.

4. 04

   Step 04 of 06

   Clean the seat and fit the new flapper

   • Time: 5 min
   • Microfiber towels

   Wipe sediment off the flush valve rim first, so the new flapper seals. Then hook each ear onto its arm.⁠[6]

   You'll know it worked when: The new flapper hangs on both arms and sits flat on a clean seat.

5. 05

   Step 05 of 06

   Clip the chain with 1 to 2 links of slack

   • Time: 3 min

   Too loose gives a slow flush; too tight keeps the toilet running.⁠[6]

   You'll know it worked when: The flapper lifts fully and drops flat.

6. 06

   Step 06 of 06

   Turn the water on and check the flush

   • Time: 5 min

   Open the valve counterclockwise. Korky's adjustable flappers have a band you turn until the flush drops the water to within a half inch of the mark.⁠[6]

   You'll know it worked when: On an adjustable flapper, the level falls to within 1/2 inch of your pencil mark.

If the new flapper still leaks, the flush valve seat may be damaged. Fluidmaster says to replace the whole flush valve when a new flapper does not stop the leak.⁠[7]

Still not fixed? Next likely cause: Fill valve clogged or worn out →

Service or replace the fill valve

The fill valve, also called a ballcock, refills the tank and the bowl after each flush and shuts off when its float rises.⁠[1] Grit and mineral scale are its main enemies.

Clean the valve first

1. 01

   Step 01 of 03

   Scrub scale off the outside

   • Time: 10 min

   Fluidmaster cleans heavy calcium buildup with vinegar and an old toothbrush, then warm soapy water and a fresh-water rinse.⁠[8]

   You'll know it worked when: The valve body moves freely and is free of crust.

2. 02

   Step 02 of 03

   Flush debris out of the valve body

   • Time: 5 min

   With the cap off, Fluidmaster sets an upside-down coffee cup over the valve, turns the water fully on for three or four seconds, then off, and does this twice.⁠[8]

   You'll know it worked when: Clean water runs from the open valve.

3. 03

   Step 03 of 03

   Clean the seal and cap

   • Time: 5 min

   Clean the seal and the cap assembly, then put them back.⁠[8]

   You'll know it worked when: The tank fills at a steady rate and shuts off quietly.

Fluidmaster suggests flushing the valve once a year, or whenever it won't shut off, and replacing the cap assembly and seal every 5 years.⁠[8]

Fit a new fill valve

Korky says fill valves typically last 5 to 7 years, depending on your water.⁠[2]

1. 01

   Step 01 of 06

   Drain the tank and sponge it dry

   • Time: 5 min
   • 5-gallon bucket

   Close the valve, flush and hold the handle down, then sponge out what is left.⁠[2]

   You'll know it worked when: The tank is empty.

2. 02

   Step 02 of 06

   Take out the old valve

   • Time: 10 min
   • Adjustable wrench

   Unscrew the supply line under the tank, with a bucket ready. Take off the mounting nut and lift the valve out.⁠[2]

   You'll know it worked when: The old valve is out and the tank hole is clean.

3. 03

   Step 03 of 06

   Set the new valve's height

   • Time: 5 min

   Korky sets its own valve this way. Too high and the valve will not shut off; too low gives weak flushes.⁠[2]

   You'll know it worked when: The water level mark on the valve sits about 1/2 inch below the top of the overflow tube.

4. 04

   Step 04 of 06

   Install it hand-tight

   • Time: 10 min

   Korky angles the valve so the refill tube has a straight path to the overflow tube. It fits the mounting nut beveled side up and tightens it by hand only.⁠[2]

   You'll know it worked when: The valve stands straight and the mounting nut is snug by hand.

5. 05

   Step 05 of 06

   Clip the refill tube to the overflow tube

   • Time: 2 min

   Korky warns that a refill tube pushed into the overflow tube can create a siphon.⁠[2]

   You'll know it worked when: The refill tube is held on the overflow tube, not pushed inside it.

6. 06

   Step 06 of 06

   Reconnect the supply and test

   • Time: 10 min

   Hand-tighten the supply nut with no sealant or tape, then open the water slowly.⁠[2] Water flowing from the refill tube, the top and the base of a Korky valve while it fills is normal.⁠[2]

   You'll know it worked when: The tank fills, shuts off at the mark and no drips show under the tank.

A slow fill after a new valve points to the supply. Korky's check is to put the supply line in a bucket and open the valve: no flow means a problem with the home's water supply and a call to a plumber.⁠[2]

Still not fixed? Next likely cause: Water level set wrong →

Set the water level

The float sets how high the water rises. Korky says a fill valve set too low leaves too little water for a full flush, and one set too high will not shut off and can run or overflow.⁠[2]

1. 01

   Step 01 of 03

   Find the mark

   • Time: 2 min
   • LED work flashlight

   Look for a waterline on the tank wall or a mark on the fill valve. Fargo says the level should match the fill line on the back of the tank.⁠[5]

   You'll know it worked when: You know the target level.

2. 02

   Step 02 of 03

   Adjust the float

   • Time: 5 min

   Turn the adjustment screw, or slide the float clip, a little at a time. Fargo also mentions very gently bending the float arm on older ball-float valves.⁠[5]

   You'll know it worked when: The tank stops filling at the mark.

3. 03

   Step 03 of 03

   Flush twice and watch

   • Time: 5 min

   If the level creeps up past the tube, the valve itself needs cleaning or replacing.

   You'll know it worked when: The water stops at the mark and stays below the top of the overflow tube.

A level that keeps changing on its own is a symptom, not a setting. See water level set too high.

Still not fixed? Next likely cause: Loose handle or wrong chain length →

Fix the handle and chain

The handle turns a lever arm inside the tank, and the arm lifts the flapper through the chain.⁠[1] Fargo's water department says a handle that must be jiggled to stop the running may be sticking, and that adjusting the nut that holds it in the tank often fixes it. If not, the handle may need replacing.⁠[5]

1. 01

   Step 01 of 02

   Snug the handle nut

   • Time: 5 min
   • Adjustable wrench

   The nut sits inside the tank, behind the handle. Turn it a little and test.⁠[5]

   You'll know it worked when: The handle moves smoothly with no wobble.

2. 02

   Step 02 of 02

   Set the chain slack

   • Time: 5 min

   Korky recommends one to two links, so the flapper lifts fully and still seals.⁠[6]

   You'll know it worked when: The chain has 1 to 2 links of slack.

If you have to hold the handle down to flush, Fargo says the chain or strap may be too long to lift the flapper high enough.⁠[5]

Still not fixed? Next likely cause: Leaking tank-to-bowl gasket or bolts →

Reseal the tank to the bowl

On a two-piece toilet, a sponge gasket seals the flush valve to the bowl,⁠[1] and bolts with rubber washers and nuts hold the tank down.⁠[3] Korky says the weight of the tank and water compresses that gasket over time, and bumping or leaning on the tank can shift it.⁠[3]

1. 01

   Step 01 of 06

   Try snugging the tank bolts

   • Time: 10 min
   • Adjustable wrench

   Korky says tightening the bolts may fix the leak, but not to overtighten them or let the tank touch the bowl, because the porcelain can crack.⁠[3]

   You'll know it worked when: The drip at the bolts stops.

2. 02

   Step 02 of 06

   Drain the tank and free the supply line

   • Time: 10 min
   • 5-gallon bucket
   • Microfiber towels

   Close the water, flush, sponge out the rest, then unscrew the supply line over a bucket.⁠[3]

   You'll know it worked when: The tank is empty and the supply line is off.

3. 03

   Step 03 of 06

   Lift the tank off

   • Time: 15 min

   Take out the old bolts, washers and nuts, lift the tank and set it on the closed toilet seat. Remove the old gasket.⁠[3]

   You'll know it worked when: The tank rests on the closed seat and the old gasket is off.

4. 04

   Step 04 of 06

   Fit the new gasket and hardware

   • Time: 10 min

   Tank-to-bowl gaskets come in 2-inch and 3-inch sizes; match yours.⁠[3] Oatey says to swap bolts with cracked rubber washers or corrosion at the same time.⁠[4]

   You'll know it worked when: The new gasket sits on the flush valve nut threads.

5. 05

   Step 05 of 06

   Bolt the tank down evenly

   • Time: 15 min
   • Adjustable wrench

   Have a partner press the tank level while you tighten the nuts, alternating sides.⁠[3]

   You'll know it worked when: The tank is level and stable, with no gap at one side.

6. 06

   Step 06 of 06

   Refill and check the joint

   • Time: 15 min
   • LED work flashlight

   Reconnect the supply hand-tight and open the water slowly.⁠[3] Oatey flushes several times, then checks with a flashlight and snugs the bolts in small steps if it seeps.⁠[4]

   You'll know it worked when: The joint and the bolts stay dry after several flushes.

If a new gasket still leaks, Korky's checklist names two things to look at: bolts tightened unevenly, and a gasket of the wrong size.⁠[3]

Still not fixed? See when to call a pro →

When to call a pro

Tank parts are a homeowner job for most people. Call a plumber when the problem goes past the tank.

Bring the brand and model, usually stamped inside the tank, so the plumber can bring the right flush valve or gasket. The same plumber visit is a good time to have a dripping tap looked at; see fix a leaking faucet.

Frequently asked questions