Short answer
A toilet that keeps running is either leaking water out of the tank or failing to shut the water off, and both are parts. Take the tank lid off and listen. A steady hiss means the fill valve is not closing. A tank that sits quiet and then refills itself every few minutes means the flapper is letting water through into the bowl. A plumber rebuilds the tank in about an hour and the toilet stays where it is.
Tell a leaking flapper from a fill valve in 20 minutes
- Lift the tank lid off and set it flat on the floor. Porcelain lids crack easily.
- Listen at the open tank. A steady hiss or the sound of moving water means water is still coming in.
- Look at the top of the overflow tube in the middle of the tank. Water spilling into it means the fill valve is set too high or is not shutting off.
- Mark the water line inside the tank with a pencil. Shut the valve behind the toilet and wait 20 minutes.
- Check the mark. Water below it means the flapper or the seat under it is leaking into the bowl.
- Drop food colouring in the tank instead if you cannot reach the valve. Colour in the bowl 15 minutes later is a flapper leak.
- Lift the handle and let it go. The chain wants about one link of slack and the flapper has to drop flat.
The level drops with the supply off, so water is escaping into the bowl and the flapper is the first part to change. The level holds and the toilet still refills, so the fill valve is not shutting off and that assembly gets replaced. Either way you are buying a part, not a toilet.
Repair or replace
| Situation | What to do |
|---|---|
| Flapper is warped, gritty or coated with mineral | Repair. A new flapper costs a few dollars and fixes most running toilets. |
| Flapper looks clean but dye still colours the bowl | Repair. The seat it lands on is pitted, so change the flush valve. |
| Chain is short or tangled, or the handle sticks down | Repair. Reset the chain with one link of slack and free the handle. |
| Steady hiss and water spilling into the overflow tube | Repair. Change the fill valve and set the level 1 inch below the top of the tube. |
| Tank was rebuilt recently and it runs again | Repair. Fit a full rebuild kit and change the flush valve, not the flapper alone. |
| Porcelain is cracked at the tank or the bowl | Replace. A cracked tank cannot be sealed and it floods the floor when it goes. |
| Toilet is over 15 years old and no flapper matches the seat | Replace. Obsolete flush valve sizes cost more to chase than a new toilet. |
What it costs
Runhome contractor estimates for this job, including the trip and assessment.
| Option | Range |
|---|---|
| Repair, tank parts and labour | $175 to $395 |
| Full replacement, new toilet plus labour | $440 to $1,090 |
Can I do it myself?
Yes. A running toilet is one of the few plumbing repairs most people finish in an afternoon. Shut the valve behind the toilet, flush to empty the tank, sponge out the rest, and change the flapper or the fill valve. Both parts sit on the shelf in every hardware store and both come with instructions.
Hire someone if the shutoff valve will not close, if water weeps from the supply line or the tank bolts, or if the porcelain is cracked.
What a contractor will ask you
Have these ready and you skip the back-and-forth.
- How long it has been running. "It's been happening for a long time" is a useful answer.
- The age of the toilet. Anything over 15 years changes the parts conversation.
- The brand. It is stamped on the bowl between your legs when seated, or inside the tank lid.
- What you hear. A steady hiss, or quiet with a refill every few minutes.
- Where the water sits between refills, right at the top of the overflow tube or below it.
- How the handle feels, normal or loose and slow to spring back.
- What the flapper looks like, warped and stained or clean and flexible.
- A wide photo of the whole toilet, plus one of the inside of the tank with the lid off.
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