Why You Shouldn't Ignore a Running Toilet
A toilet that runs continuously isn't just annoying — it wastes a significant amount of water and adds noticeably to your water bill. The good news is that the vast majority of running toilet issues are caused by a small number of simple, inexpensive problems that you can fix yourself in under an hour with basic tools.
What You'll Need
- Adjustable wrench or pliers
- Rubber gloves
- Replacement flapper (available at any hardware store, typically inexpensive)
- Replacement fill valve (optional, if needed)
- Paper towels and a sponge
Understanding How a Toilet Works
Before diving in, it helps to know the basics. When you flush, the flush valve opens, water drains from the tank into the bowl, and the fill valve refills the tank. A float rises with the water level and signals the fill valve to shut off when the tank is full. The flapper is the rubber seal at the bottom of the tank — it's the most common culprit in running toilets.
Step 1: Diagnose the Problem
Remove the toilet tank lid and set it safely aside. Observe what's happening:
- Water running into the bowl: The flapper is likely worn or not sealing properly.
- Water running into the overflow tube: The water level is too high — the float or fill valve needs adjusting.
- Fill valve making noise but not shutting off: The fill valve may need replacing.
Quick test: Put a few drops of food colouring into the tank. If colour appears in the bowl without flushing, your flapper is leaking.
Step 2: Replace the Flapper
This is the most common fix and takes about 10 minutes:
- Turn off the water supply valve behind or beneath the toilet (turn clockwise).
- Flush to drain the tank.
- Unhook the old flapper from the pegs on either side of the flush valve and disconnect the chain from the flush handle arm.
- Take the old flapper to a hardware store to match the size, or purchase a universal flapper.
- Hook the new flapper onto the pegs and attach the chain, leaving about 1–2cm of slack.
- Turn the water supply back on and test.
Step 3: Adjust the Float
If water is running into the overflow tube, the water level in the tank is too high. The float needs to be lowered:
- Ball float (old-style): Bend the float arm downward slightly, or turn the adjustment screw on the fill valve.
- Cup float (modern style): Pinch the clip on the side of the float and slide it down the fill valve shaft.
The water level should sit approximately 2–3cm below the top of the overflow tube.
Step 4: Replace the Fill Valve (If Needed)
If adjusting the float doesn't stop the noise and running, the fill valve itself may be worn and need replacing. Replacement fill valves are readily available and designed to be DIY-friendly:
- Turn off the supply valve and flush the toilet.
- Use a sponge to remove remaining water from the tank.
- Disconnect the water supply line from the bottom of the tank.
- Unscrew the locknut securing the fill valve and lift it out.
- Insert the new fill valve, tighten the locknut, reconnect the supply line, and turn water back on.
- Adjust the height and float level per the manufacturer's instructions.
When to Call a Plumber
If you've replaced the flapper and fill valve and the toilet is still running, or if you notice cracks in the tank or bowl, it's time to call a licensed plumber. However, the steps above resolve the overwhelming majority of running toilet issues without professional help.