How to Diagnose and Fix a Leaky Toilet

One constantly running toilet can add as much as $20 or more to your monthly water bill and can waste approximately 24 gallons of water per day which amounts to 720 gallons per month.

Fixing a leaky toilet is easy and cheap, after you diagnose the problem.

Our troubleshooting guide below will help you uncover the cause and show you how to fix the problem. Learning how to diagnose and possibly even prevent a repair call will save you money in the long run.

Troubleshooting Guide: Running Toilet

Possible Cause	How to Fix It
Flapper not seated properly	Flush toilet or clean flapper seat
Tank handle stuck	Service handle
Water level in tank too high	Reposition or replace float ball Adjust water intake assembly
Lift chain short or tangled	Adjust or replace lift chain
Fill valve faulty	Replace fill valve
Flush valve leaking	Service or replace flush valve Clean valve seat or replace flush valve assembly

Service the handle

Remove the tank cover and carefully lay it aside. For a loose tank handle, tighten the locknut inside the tank counterclockwise (with a wrench for older style toilets.)

If the nut is impossible to remove, cut through the handle shaft with a hacksaw and replace the handle and the trip lever. Unlock the chain from the trip lever and slide the trip lever with the handle attached through the hole in the tank. Scrub the handle threads with a toothbrush and vinegar. Reinstall the assembly tightening the locknut counterclockwise.

Adjust or replace the lift chain

If the handle must be held down to flush the toilet, the chain is too long. To shorten it try to hook the chain through a different hole in the handle arm or move the hook to a different chain link. If water is constantly running inside the bowl, it may indicate that the chain is too short. To lengthen it, you must replace the chain. Do not try to make it longer with safety pins or wire because a second metal will promote corrosion. To adjust the length an older flush assembly, loosen the screw on the guide arm, then slide the guide arm up to shorten, or down to make it longer.

Adjust the float ball arm

If the water level in the water tank is too high it will start overflowing through the overflow pipe and in the toilet bowl. To adjust the metal arm, just bend it until the fill valve stops when the water level reaches around an inch below the top of the overfill valve. Make sure that the float does not touch the wall of the tank and moves freely up and down. If the ball arm is plastic, unscrew the bolt at the base of the arm and move it up and to place it at the desired position.

Replace the float ball

If the float is cracked or otherwise damaged, it probably have water inside affects its ability float do its job properly. In this case you should replace it. Hold the float arm with pliers and unscrew the float with your hand counterclockwise then screw the new float to the arm. If when you lift arm to the upmost position doesn’t stop the water from filling the tank, you need to replace the fill valve with a new one.

Adjust the water intake assembly

First, flush the toilet to empty the water tank and let it fill until the fill valve stops. Check the water level. It should be around an inch below the top of the overflow pipe. To adjust the level, use a screwdriver to turn the screw that connects the float with the fill valve lever right or left until the float reaches the desired position.

Replace the fill valve

There two choices for a fill valve replacement:

Ball float and an arm
Newer plastic water intake assembly.

The second option is preferable because it’s more compact and more reliable. Both types of valves are interchangeable so you don’t have to worry if it’s going to fit in your toilet.

Steps to remove and replace the fill valve

Shut off the water supply by closing the shutoff valve underneath the water tank. After that, flush the toilet to empty the tank and make sure that no water is coming in the tank. If water continues to fill the tank, the shutoff valve doesn’t hold and you need to close the main shutoff valve.
Place a container to catch the rest of the water when removing the fill valve because when you flush the toilet, some water remains in the tank. Remove the supply hose using pipe pliers, locking pliers, or a wrench depending on the type of the hose.
Remove the refill tube from the overflow pipe, and use the same tools to unscrew the nut underneath the tank while holding the valve from inside to prevent it from moving with the nut. Remove the old valve, clean the hole with a rag or a sponge, and install the new one using the same steps in reverse order. When finished with the installation, turn the shutoff valve slowly and look for leaks. If no leaks occur, adjust the water level in the water tank.

How to replace the flapper valve

Before replacing the valve, try to clean the valve seat. Shut off the water supply or hold the fill valve float at its highest position then flush the toilet. Lift the flapper and clean the seat with a soft rag or sponge. Do not scrape it with a knife or anything else that can damage the seat. If the leak continues, replace the valve.

Shut off the water supply and flush the toilet. Unhook the lift chain from the handle arm and remove the flapper by unhooking its ‘ears’ from the seat or sliding it up the overflow pipe (depends on the flapper type).
Make sure that the new flapper is the same size as the old one. Install the new flapper and attach the lift chain to the handle arm.
Adjust the chain’s length so it’s not too short or too long. If the toilet doesn’t flush or you need to hold down the handle to do so, the chain is too long. If water leaks inside the bowl, the chain is too short.

If after the valve is replaced and the chain is properly adjusted the leak doesn’t stop, you have to replace the whole flush valve assembly.

How to replace the flush valve assembly

To replace the valve assembly, you need to remove the tank.

Stop the supply valve, flush toilet, remove the water supply line, and try to remove as much of the remaining water as you can.
Water tanks are attached to toilets with two or three bolts and the nuts you need to remove are underneath the toilet rim. You will need a screwdriver to keep the bolts from rotating with the nuts, a wrench (usually ½) or an adjustable wrench (sometimes the space is too tight to move it around). Unscrew the nuts, remove the tank by lifting it up. The new assembly kit comes with new bolts so remove the old ones. It is important to take notes how the metal and rubber washers are arranged.
Remove the conical gasket from the bottom of the tank. Use a spud wrench or a monkey wrench to unscrew the retaining nut and remove the assembly when done. Note that there’s a gasket between the assembly and the inside bottom of the tank.
Clean the bottom of the tank especially where the gasket sits. Insert the new assembly into the hole and hold it at the exact same orientation as the old one was while tightening the retaining nut on the other side. Do not overtighten because the thread is plastic. Place the new conical gasket over the retaining nut and make sure it’s completely covered by the gasket.
Take a look at your notes and Install the new bolts the same way old ones were installed.
Place the water tank back on its seat and secure it with the new nuts (metal washer first, then the nut). Tighten the nut until the bottom of the tank (both front and back) touches the toilet surface. Do not overtighten. The tank is porcelain and you can break it by doing so.
Place the fill tube back inside the overflow pipe, connect the lift chain to the handle arm, and adjust the chain’s length.
Reconnect the water supply line, open the shutoff valve, and inspect for leaks.