Why You Should Fix It Now
A constantly running toilet isn't just annoying — it can waste a significant amount of water every day, which adds up on your water bill over time. The good news: in the vast majority of cases, a running toilet has one of three simple causes, each easily fixed with inexpensive parts available at any hardware store. You don't need plumbing experience to handle this.
What You'll Need
- Adjustable wrench or pliers
- Rubber gloves
- Replacement flapper (a few dollars at any hardware store)
- Replacement fill valve (optional, if the flapper doesn't fix it)
- Paper towels or a sponge
Step 1: Diagnose the Problem
Remove the tank lid (the flat cover on top of the toilet, not the seat) and set it aside carefully — it's porcelain and can crack if dropped. Look inside and observe what's happening. There are three main culprits:
- Flapper issues: The flapper is the rubber seal at the bottom of the tank. If it's worn, warped, or not sealing properly, water continuously leaks from the tank into the bowl — causing the toilet to "run" to refill constantly.
- Float set too high: The float controls when the tank stops filling. If it's set too high, water overflows into the overflow tube continuously.
- Faulty fill valve: The fill valve (also called the ballcock) controls water flowing into the tank. If it's worn out, it may not shut off properly.
Quick test for a leaking flapper: Add a few drops of food coloring to the tank and wait 10–15 minutes without flushing. If color appears in the bowl, your flapper is leaking.
Step 2: Fix a Worn Flapper
This is the most common fix and takes about 10 minutes:
- Turn off the water supply. Find the shut-off valve on the wall behind the toilet and turn it clockwise until it stops.
- Flush the toilet to empty the tank.
- Unhook the old flapper. The flapper typically unclips from two pegs on either side of the overflow tube and detaches from the chain connected to the flush handle.
- Take the old flapper to the hardware store to match the size, or note your toilet's brand and model. Universal flappers fit most toilets.
- Clip the new flapper onto the same pegs and reattach the chain to the flush arm. Leave about half an inch of slack in the chain — too tight means the flapper won't seal; too loose means it may catch under the flapper.
- Turn the water back on and let the tank fill. Test the flush and listen for any continued running.
Step 3: Adjust the Float Level
If water is running into the overflow tube (the tall tube in the center of the tank), your float is set too high. The water level should sit about 1 inch below the top of the overflow tube.
- Ball float (older style): Bend the metal arm slightly downward, or turn the adjustment screw on the arm to lower the float.
- Cup float (modern style): Pinch the clip on the side of the fill valve and slide the float down. Some models have a screw adjustment at the top of the fill valve.
Flush and observe — the water should stop filling at the correct level.
Step 4: Replace the Fill Valve
If adjusting the float doesn't work and the fill valve is visibly worn or doesn't shut off properly, replace it. Fill valves are inexpensive and widely available. The process involves:
- Turning off the water supply and flushing to empty the tank.
- Disconnecting the water supply line from the bottom of the tank.
- Unscrewing the locknut under the tank that holds the fill valve in place.
- Lifting out the old fill valve and dropping in the new one, following the manufacturer's instructions to set the height.
- Reconnecting the supply line and the refill tube to the overflow pipe.
- Turning the water back on and adjusting the float to the correct level.
When to Call a Plumber
If you've replaced the flapper and fill valve and the toilet still runs, or if you notice cracks in the porcelain tank or bowl, it's time to call a professional. But in most cases, a running toilet is one of the most accessible DIY plumbing repairs a homeowner can tackle — and fixing it yourself saves both water and money.