That quiet hissing or trickling sound from your toilet — you can hear it from the hallway, especially at night. A running toilet is the most common plumbing complaint in residential homes, and it's also one of the most wasteful. A single running toilet can waste 200 gallons of water per day, adding $50–$100 to your monthly water bill.
The 4 Most Common Causes of a Running Toilet
1. Worn or Warped Flapper
The flapper is a rubber seal at the bottom of the toilet tank that opens when you flush and closes to hold water until the next flush. Over time, rubber warps, hardens, or develops mineral deposits that prevent it from sealing completely. Even a tiny gap allows water to continuously leak from the tank into the bowl.
DIY fix: Flappers cost $3–$8 at any hardware store and take 10 minutes to replace. Turn off the water supply valve behind the toilet, flush to empty the tank, unhook the old flapper, snap on the new one, and turn the water back on.
2. Float Set Too High
The float controls the water level in the tank. If it's set too high, water reaches the overflow tube (the tall vertical tube in the center of the tank) and drains continuously into the bowl. You can hear a constant trickle and see water running down the inside of the bowl.
DIY fix: Adjust the float by bending the float arm slightly downward (on ball-float systems) or turning the adjustment screw (on cup-float systems). Water should stop 1 inch below the top of the overflow tube.
3. Fill Valve Failure
The fill valve refills the tank after each flush. When it fails, it doesn't shut off properly and water runs continuously into the tank (and then out via the overflow tube). You'll hear a steady, high-pitched hissing even when the tank is full.
Fix: Fill valve replacement is a straightforward repair that costs $15–$20 in parts. Most homeowners can do this themselves, or a plumber can replace it in under 30 minutes.
4. Flush Valve Seat Damage
If you've replaced the flapper and the toilet is still running, the problem may be the flush valve seat — the ring the flapper seals against. Hard water deposits or cracks in the seat prevent a complete seal. You can feel the seat with your finger; if it's rough or uneven, it needs resurfacing or replacement.
Fix: Use a flush valve seat repair kit to resurface minor deposits, or replace the entire flush valve (this requires partial tank disassembly — a plumber is recommended).
When to Call a Plumber Instead of DIY
- You've replaced the flapper and fill valve but the toilet still runs
- Water is leaking at the base of the toilet (wax ring failure — completely different issue)
- The tank cracks when you remove the lid
- The toilet is more than 15 years old — at that point, a new high-efficiency toilet may save more water and money than multiple repairs
If you're not comfortable with the repair or the problem persists, call Prestige Plumbing Services at (818) 688-1595. We handle toilet repairs and full replacements throughout Burbank, Glendale, and the San Fernando Valley — usually same day.
