How to Fix a Toilet That Keeps Running — No Plumber Needed
That non-stop hissing sound is wasting thousands of litres of water every year. The good news? In 9 out of 10 cases, it’s a tiny rubber part that costs less than $10 and takes 20 minutes to swap.
Found this helpful? Share it with someone who needs it.
A running toilet is almost always caused by a worn-out flapper — a small rubber seal at the bottom of your tank. Turn off the water, flush to drain the tank, unhook the old flapper, take it to any hardware store for a matching replacement (costs $5–$12), snap the new one in, and you’re done. The whole job takes about 20 minutes.
Why is your toilet running — and why does it matter?
When you flush, water rushes from the tank into the bowl through an opening at the bottom of the tank. A rubber seal called the flapper drops back over that opening to hold the next tank of water. When the flapper wears out, it doesn’t seal properly — water slowly trickles from the tank into the bowl, the tank level drops, and the fill valve kicks in to top it up again. Over and over. All day and night.
This invisible leak can waste up to 200 litres of water every single day — the equivalent of four full baths. Over a year, that’s a serious increase in your water bill for something that costs less than a coffee to fix.
Drop 5–6 drops of food colouring into the tank without flushing. Wait 10–15 minutes. If the colour appears in the bowl, water is leaking — and you need this guide. This works even for silent leaks you can’t hear.
The three most common causes (and which one you have)
Before you go to the hardware store, spend two minutes identifying what’s actually wrong. Lift the lid off your tank and look inside. Here’s what each problem looks like:
| What you see or hear | Likely cause | Difficulty | Cost |
|---|---|---|---|
| Constant hissing or trickle into bowl | Worn flapper — most common cause | ⭐ Easy | $5–$12 |
| Water level too high, spilling into overflow tube | Float set too high or fill valve fault | ⭐ Easy | $0–$15 |
| Water runs for a long time after flushing | Flapper chain too short or tangled | ⭐ Very easy | $0 |
| Toilet flushes by itself (“ghost flush”) | Flapper leak — slow version of above | ⭐ Easy | $5–$12 |
| Water dripping outside the tank | Cracked tank or loose bolts — call a plumber | Call a pro | Varies |
This guide covers the three most common DIY fixes: replacing the flapper, adjusting the chain, and adjusting the float. Together they solve the problem about 95% of the time.
A clear 4-minute walkthrough of replacing a toilet flapper. Watch this alongside the written steps if you prefer to see it done first. (If this video is unavailable in your country, search YouTube for “how to replace toilet flapper” — there are many excellent free tutorials.)
What you’ll need
Good news: you probably won’t need any tools at all. Flappers are designed to be replaced by hand.
- A replacement flapper — take the old one to any hardware store or superstore and match it. Universal flappers ($5–$8) fit most toilets. Exact-match flappers are slightly better if you can find them.
- A sponge or old towel — to mop up water left in the tank after flushing
- Rubber gloves — optional, but useful if you prefer not to get your hands wet
- Adjustable pliers — only needed if you’re also replacing the fill valve (Step 6 below)
▸ These are affiliate links — we may earn a small commission if you buy through them, at no extra cost to you. See our Affiliate Disclosure.
Fix 1: Replace the flapper (most common fix)
This fix solves the problem about 8 times out of 10. It takes 20 minutes and requires no tools.
Once the tank is full and you’ve flushed, repeat the food colouring test from earlier. Put a few drops in the tank, wait 10 minutes, and check the bowl. No colour = perfect seal. You fixed it.
Fix 2: Adjust the chain (free — takes 2 minutes)
Before replacing anything, check the chain. This is the simplest possible fix and it’s free. If the chain is twisted, tangled, or has too much slack, it can get caught under the flapper and hold it open just enough to let water trickle through.
- Lift the tank lid and look at the chain connecting the flapper to the flush arm
- The chain should have just a small amount of slack — enough to lie loosely but not bunch up
- If there’s too much slack, clip the chain to a different hole on the flush arm (closer to the handle)
- If the chain is too short and holding the flapper open, you can buy a chain extension at the hardware store for about $2
- Flush and check if the running stops
Fix 3: Adjust the water level (if water is spilling into the overflow tube)
Look inside the tank while it’s filling. If the water level is rising above the top of the tall plastic tube in the middle (called the overflow tube), that’s your problem — water is constantly spilling down into the bowl.
The fix is to lower the water level by adjusting the float — the part that tells the fill valve when to stop adding water.
- Ball-float type (older toilets): Bend the metal arm downward slightly, or turn the adjustment screw at the end of the arm clockwise
- Cup-float type (modern toilets): Pinch the clip on the side of the fill valve and slide it downward to lower the float level
- The correct water level is about 2–3 cm (1 inch) below the top of the overflow tube
This short video shows exactly how to adjust both types of float — ball-float and cup-float. Takes less than 5 minutes once you know what to look for.
How much money will you save?
Let’s put some real numbers on this.
Beyond the repair cost, a running toilet that wastes 200 litres a day adds roughly $100–$200 to your annual water bill, depending on where you live and your tariff. The faster you fix it, the more you save.
When to call a plumber
Most running toilets are easy DIY fixes. But call a qualified plumber if:
- You’ve replaced the flapper and adjusted the float and it’s still running
- You can see water on the outside of the tank or on the floor around the toilet
- The supply valve behind the toilet is stuck or corroded and won’t turn
- The flush valve seat (the plastic ring the flapper sits on) feels rough or has cracks — this requires replacing the entire flush valve, which is a bigger job
- You’re simply not comfortable with any of the steps above — and that’s completely fine
If water is pooling on the floor outside the toilet, this is not a flapper issue. Turn off the water supply immediately and call a plumber — this can damage your floor and ceiling below very quickly.