Why Is My Toilet Always Running? How to Fix It

That constant hiss or trickle from your toilet isn't just annoying — a running toilet can waste hundreds of gallons of water a day and quietly inflate your bill. The good news is that most causes are inexpensive parts you can often fix in under an hour.

Start by looking inside the tank

Take the lid off the tank and flush. Watch what happens as the tank refills — the culprit is almost always one of three parts: the flapper, the fill valve, or the float.

1. A worn or warped flapper (most common)

The flapper is the rubber seal at the bottom of the tank. Over time it warps or gets a mineral crust — common with our hard water — and stops sealing. Water then leaks past it into the bowl, and the tank keeps refilling. Try this test: put a few drops of food coloring in the tank and wait 15 minutes without flushing. If color appears in the bowl, the flapper is leaking and should be replaced.

2. A bad fill valve

If the tank never stops filling or you hear a constant hiss, the fill valve may be worn or set incorrectly. Fill valves are inexpensive and straightforward to replace, and a new one usually eliminates the noise entirely.

3. The float is set too high

If water is spilling into the overflow tube, the float is set too high, so the tank overfills and drains continuously. Lowering the float (bending the arm or adjusting the clip) sets the correct water level, usually about an inch below the top of the overflow tube.

How to replace a flapper (the most common fix)

1. 1Turn off the water at the valve behind the toilet and flush to empty the tank.
2. 2Unhook the old flapper from the flush valve, and the chain from the flush lever.
3. 3Match it at the hardware store, or buy a universal replacement flapper.
4. 4Clip the new flapper onto the flush valve and connect the chain with a little slack.
5. 5Turn the water back on, test a few flushes, and adjust the chain so the flapper seals fully.

Other common toilet problems

• Weak or partial flush: often mineral buildup in the rim jets — common with hard water — or a flapper closing too soon.
• Phantom flushing (the tank refills on its own): almost always a slow flapper leak letting the tank drain into the bowl.
• Gurgling or slow-draining bowl: can signal a partial clog or a venting issue rather than a tank part.

When it's more than a running toilet

If your toilet is also rocking, leaking at the base, or clogging constantly, that's a different problem — often a failed wax ring or a partial blockage — and it's worth having a plumber look before it damages your subfloor. We handle toilet repairs across the West Valley, including Glendale and Avondale.

Why it's worth fixing fast

A single running toilet can waste more water than a family uses in a day. Fixing it protects both your water bill and, in the case of a leaking base, your flooring. If you'd rather not troubleshoot it yourself, we can have it handled quickly and affordably.