That faint hiss or the tank refilling for no reason in the middle of the night usually means one thing: your toilet is running. It’s one of the most common household annoyances, and it can waste a surprising amount of water. The good news is that most running toilets can be fixed in under an hour with basic tools and an inexpensive part.
What you’ll need
- A towel or sponge.
- Rubber gloves.
- An adjustable wrench or pliers.
- A replacement flapper or fill valve, if needed. Take the old part to the store so you can match it.
- Food coloring (optional, for testing).
How a toilet tank works, in 30 seconds
When you flush, a rubber flapper at the bottom of the tank lifts and lets water rush into the bowl. When the tank empties, the flapper drops back down to seal the opening. The fill valve then refills the tank until a float rises to the right level and shuts off the water. A running toilet means one of these steps isn’t finishing properly.
Step 1: Take a look inside
Lift the tank lid and set it somewhere safe, since lids are heavy and break easily. Flush and watch what happens. Pay attention to the flapper, the chain and the water level once refilling stops.
Step 2: Check the water level
Look for the overflow tube, the open vertical pipe in the middle of the tank. If water is spilling into it, the water level is set too high and the toilet will keep running.
Most modern fill valves have an adjustment screw or a clip on the float. Lower the float a little so the water stops about an inch below the top of the overflow tube. Many tanks have a water-level line marked inside.
Step 3: Inspect the chain
The chain connects the flush handle to the flapper. If it’s too short, it holds the flapper slightly open. If it’s too long, it can get caught underneath the flapper and stop it from sealing.
Adjust it so there’s just a little slack when the flapper is closed. Most chains clip on with a small hook, so you can move it a link or two at a time.
Step 4: Test the flapper
The flapper is the most common culprit. Over time, rubber can warp, stiffen or collect mineral buildup, so it no longer seals.
A simple test: add a few drops of food coloring to the tank water and wait 15 to 30 minutes without flushing. If colored water shows up in the bowl, the flapper is leaking.
Sometimes cleaning the flapper and the rim it sits on with a cloth is enough. If the rubber feels stiff or looks warped, replace it.
Step 5: Replace the flapper
- Turn off the water supply valve behind the toilet, usually by turning it clockwise.
- Flush to drain the tank and sponge out the rest.
- Unhook the chain and slide the old flapper off its mounting pegs on the overflow tube.
- Attach the new flapper the same way and reconnect the chain with a little slack.
- Turn the water back on and test a few flushes.
Step 6: When the fill valve is the problem
If the flapper seals but water keeps trickling in or the valve hisses, the fill valve may be worn. Some can be cleaned by removing the cap and flushing out debris, following the manufacturer’s instructions.
Replacing the whole fill valve is a slightly bigger job but still very doable: shut off the water, drain the tank, disconnect the supply line under the tank, remove the old valve, install the new one at the correct height and reconnect. Follow the instructions in the package, since designs differ.
When to call a plumber
Call a professional if you notice water leaking around the base of the toilet, cracks in the tank or bowl, a supply valve that won’t turn off or a leak you can’t trace. Those can point to bigger issues, and water damage gets expensive quickly.
The bottom line
A running toilet is usually a small problem with a small fix: adjust the water level, give the chain a bit of slack or swap a worn flapper. Spend a few minutes diagnosing before you buy parts, and you’ll likely have peace and quiet back in your bathroom by the end of the afternoon.
Image: Bathroom with bathtub, toilet and sink at the Leiden University Medical Center, AHM-F-5989-151 by Hendrik Jonker via Wikimedia Commons, Public Domain Mark 1.0
