Reel Four: The Tank
Why Your Toilet Keeps Running
A hiss in the night. A tank that refills on its own. Few household faults are as common as a running toilet among nuisances, and most fixes are simple.
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The short version
A toilet runs for one of three reasons. The flapper lets water seep down into the bowl. The fill valve is not shutting off. Or the water level is set too high and spills into the overflow tube. Lift the tank lid and you can usually see which one in a minute.
What you notice, what we usually find
| Symptom | Likely cause |
|---|---|
| Hiss every few minutes | Worn flapper letting water seep into the bowl |
| Tank level creeping over the overflow pipe | Float adjusted high, or a fill valve on its way out |
| You rattle the lever to make it stop | Slack lift chain or a kinked trip arm |
Step by step
- Close the supply valve. It is the small valve on the wall behind the toilet. Turn it clockwise.
- Lift the lid. Set it on a towel. Porcelain chips easily.
- Check the overflow. If water is running into the open-topped tube in the middle, the level is too high. Adjust the float on the fill valve down a little.
- Test the flapper. Put a couple of drops of food dye in the tank and hold off twenty minutes without flushing. Colour in the basin means the flapper is leaking.
- Look at the chain. A chain that is too taut holds the flapper slightly open. Too loose and it can tangle underneath. Leave a little slack.
- Replace the flapper. Take the old one to a hardware store to match the size and style. Most unclip from two ears on the overflow tube.
- Replace the fill valve if needed. If the valve hisses or will not close off after adjusting, a new one is often the cleaner fix.
A toilet that runs silently can still waste a large amount of water. If your water bill rises for no clear reason, this is the first place to check. See reading your water bill.
Mistakes to avoid
- Buying a universal flapper that does not fit. Size and shape matter, especially on newer low-flow models.
- Overtightening plastic nuts on the supply connection. They crack.
- Using in-tank bleach tablets. They can speed up wear on rubber parts.
- Bending a float arm on an old ballcock and hoping. Replacing it is more reliable.
- Ignoring mineral buildup. Halton's moderately hard water leaves deposits on the flush valve seat that stop a new flapper from sealing. Wipe the seat clean when you swap parts.
What you need
Most running toilet fixes call for very little. A replacement flapper or fill valve sized for your toilet, a sponge and towel for the last of the water in the tank, and perhaps an adjustable wrench for the supply nut. Take a photo of the within of the tank before you start so you can match the parts and remember how the chain was set. Many brands print the model number inside the tank behind the waterline, which makes finding the right parts much easier.
Stop and phone a plumber when
- 1A ceiling or wall starts dripping
- 2More than one drain backs up at once
- 3You smell gas or sewage indoors
- 4A valve will not turn or drips when touched
When to call
Call if the tank drips onto the floor, the flush valve itself is cracked, the supply valve will not close, or you have tried new parts and it still runs. Call too if the bowl rocks or water appears around the base. Those point to a seal or flange problem, covered under toilet repair. For a full replacement, see toilet installation.
Straight answers to common calls
Why does my toilet run for a couple of seconds every so often?
Water is gradually leaking from the tank into the bowl, and the fill valve tops it back up. A new flapper typically fixes it.
How do I lower the water level in the tank?
Most modern fill valves have a float on the shaft with an adjustment clip or screw. Lower it so the water sits below the top of the overflow tube.
Keep reading
- Toilet Repair in Oakville
It runs all night.
- Toilet Installation in Oakville
A cracked bowl, a renovation, or a thirsty old model.
- Things That Should Never Go Down a Drain
A toilet line is meant to carry three things only: water, human waste, and toilet paper.
Ready when you are
One call books the visit. Tell us what you are seeing and we will tell you straight what it likely is.