Quick answer
A running toilet is most often caused by a worn flapper that no longer seals the tank. Other causes are a chain that is too tight, a misadjusted float, or a faulty fill valve. A few drops of food coloring in the tank will confirm a leak. Many of these repairs take minutes and use inexpensive parts.
How much water a running toilet wastes
The EPA says household leaks waste an average of about 9,400 gallons per year for a typical family, roughly 180 gallons per week, and that toilets are often the cause. Nine percent of homes have leaks that waste 50 gallons or more per day.
A silent leak can be worse than one you can hear. EPA notes that a worn flapper can leak thousands of gallons a year without obvious signs, and that most toilet leaks come from old or worn-out flappers.
Fixing easily corrected household leaks can save about 10 percent on a water bill, according to EPA.
Step 1: Run the dye test
Before you replace anything, confirm that the toilet is leaking from the tank into the bowl.
- Lift the tank lid and put a few drops of food coloring in the tank. Do not flush.
- Wait at least 10 minutes. EPA says that if any color shows up in the bowl in that time, you have a leak. Some guides suggest waiting up to 20 minutes for a slow leak.
- Flush right away when you are done so the dye does not stain the tank.
- If the bowl stays clear but the toilet still runs or refills now and then, look at the fill valve, float and overflow tube instead.
Step 2: Check the flapper and chain
The flapper is the rubber seal at the bottom of the tank that lifts when you flush and drops to close the opening. It is the most common cause of a running toilet. It can get stiff, warped or coated with mineral buildup and stop sealing.
EPA recommends checking flappers periodically and replacing them at least every five years.
The chain connects the flush lever to the flapper. It should have a little slack when the flapper is closed. If it is too tight, it can hold the flapper slightly open and cause a constant trickle. If it is too loose, the flapper will not lift enough to flush.
- Shut off the water at the valve on the wall behind the toilet and flush to empty the tank.
- Unhook the chain and lift out the old flapper. Take it, or a photo, to the store. EPA advises checking its width and whether it has a foam float that also needs replacing.
- Wipe the flush valve seat (the rim the flapper sits on) clean. Minor corrosion can be scoured off with a scouring pad.
- Install the new flapper, reattach the chain with slight slack, turn the water back on and test.
Step 3: Check the fill valve and float
The fill valve refills the tank after a flush and shuts off when the float tells it the water is high enough. If it does not shut off, water keeps running into the overflow tube.
Look at the water level. It should sit about an inch below the top of the overflow tube. If water is spilling into the tube, adjust the float or the fill valve height to lower it.
A float that sits too low on the chain can also keep pulling on the flapper. Set it near the water line when the tank is full.
Debris in the fill valve can stop it from closing. With the water off, flush, remove the fill valve cap, and briefly run water to flush out debris, then scrub parts with a soft brush. If cleaning does not fix it, replace the fill valve, following the manufacturer's instructions. Remove the remaining tank water first with a sponge or wet vac.
Other causes
A cracked or poorly set overflow tube can let water escape. Inspect it for cracks. A severely corroded flush valve seat may require replacing the whole flush valve assembly.
If you see water on the floor around the base of the toilet, or under the tank, that is a different problem, such as a failed wax ring, loose bolts or a bad supply line connection. Shut off the water supply and have it looked at.
Should you replace the toilet?
Most running toilets do not need replacing. Replace the parts first. Consider a new toilet if the tank or bowl is cracked, if the porcelain leaks, if repairs keep failing, or if the toilet is an old high-flow model.
EPA says older inefficient toilets can use as much as 6 gallons per flush. WaterSense labeled toilets use 1.28 gallons per flush or less, which is 20 percent less than the 1.6 gallon federal standard. EPA estimates that replacing old toilets with WaterSense models can cut toilet water use by 20 to 60 percent, nearly 13,000 gallons per year for an average home. Toilets account for nearly 30 percent of indoor home water use.
These are national averages. Your savings depend on the age of your toilet and how many people use it.
If the toilet is clogged
A clogged toilet is a separate problem from a running one, but it often shows up at the same time. Do not keep flushing. Put towels around the base, and use a cup to remove excess water from a full bowl.
Use a flange-style plunger made for toilets. Seal it over the drain opening and plunge for 20 to 30 seconds, pulling back more than pushing down, then flush to check. If you use a closet auger, avoid a standard hand snake, which can scratch the porcelain. Wear gloves and clean tools afterward.
Do not use chemical drain cleaners in a toilet. They can burn skin and eyes, and mixing them with other cleaners can release toxic gas. If clogs keep coming back or sewage backs up into other drains, stop and call a plumber.
When to call Pyper
Call a plumber if the toilet keeps running after you replace the flapper and adjust the fill valve, if water is leaking onto the floor, if the tank or bowl is cracked, or if you are not comfortable working inside the tank. Overflowing toilets and active leaks should be treated as urgent: shut off the supply valve first.
Pyper Plumbing repairs and installs toilets and handles leak detection and emergency plumbing across Snohomish, Skagit, Whatcom and Island counties. If you are unsure whether the problem is a simple tank part or something bigger, give us a call.
Common questions
Why does my toilet keep running after I flush?
The most common cause is a worn flapper that does not seal. Other causes include a chain that is too tight, a float set too low, a fill valve that will not shut off, or water level above the overflow tube.
How do I test a toilet for a leak?
Put a few drops of food coloring in the tank without flushing. If color appears in the bowl after 10 minutes, EPA says you have a leak. Flush right after the test to avoid staining.
How much water does a running toilet waste?
It varies. EPA says average household leaks waste about 9,400 gallons a year and that worn flappers can leak thousands of gallons a year without obvious signs. Many toilet leaks are silent.
How often should a flapper be replaced?
EPA recommends checking flappers periodically and replacing them at least every five years. Replace sooner if the toilet runs, refills on its own, or the dye test shows color in the bowl.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- EPA WaterSense: Fix a Leak Week
- EPA WaterSense: Statistics and Facts
- EPA WaterSense: Residential Toilets
- This Old House: How to Fix a Running Toilet
- This Old House: How to Unclog a Toilet
- Poison Control: Caution with Caustics
- NJ Department of Health: Hazard Alert, Mixing Cleaners
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
