Toilet Water Running Into the Overflow Tube? How to Fix It

Quick answer: if tank water keeps spilling into the overflow tube (the open pipe in the middle of the tank), the water level is set too high or the fill valve is not shutting off. Lower the float so the water stops about ½ to 1 inch below the top of the overflow tube. If lifting the float by hand does not stop the water, clean or replace the fill valve. A worn flapper is a different problem: it leaks into the bowl through the flush seat, not over the top of the tube.

Is it the overflow or the flapper?

Lift the tank lid after a flush and watch the tank refill all the way.

Water rises to the rim of the overflow tube and pours down inside it, and the fill valve keeps hissing. That is a fill-level or fill-valve problem. Keep reading.
Water stops well below the tube, then slowly drops and the valve turns back on every so often. That is a flapper or flush-seat leak. Start with Toilet keeps running — flapper check first.
A thin stream from the small rubber refill tube goes into the overflow while the tank refills. That is normal. It refills the bowl and should stop when the fill valve shuts off.

A dye test settles it: put a few drops of food coloring in the tank and wait 15 to 20 minutes without flushing. Color in the bowl with the water still below the tube means the flapper is leaking.

How to stop water going into the overflow tube

1. Find the right water level

Look for a water line mark stamped on the inside of the tank or on the fill valve. If there is none, aim for ½ to 1 inch below the top of the overflow tube.

2. Lower the float

Leave the water on. Adjust in small steps and flush between each one.

Float cup (a cup that slides up and down the fill valve body, the most common modern style): turn the adjustment screw or knob on top of the valve to lower the cup, or squeeze the metal clip on the adjustment rod and slide the cup down about ½ inch.
Ball float (a ball on a long arm on older valves): turn the adjustment screw where the arm meets the valve, or gently bend a brass arm slightly downward. Do not bend plastic arms.
Floatless or pressure-sensing valve: use the dial or screw the maker provides. The instructions are usually printed on the valve.

More detail in Check toilet fill valve float height.

3. Flush and watch a full refill

The fill valve should shut off on its own with the water below the top of the tube. If the water still creeps up into the tube, lower the float another step.

4. Check the refill tube

The small refill tube should clip to the overflow with its end above the water, not pushed down inside. A submerged tube can siphon tank water and make the valve cycle. See Keep the refill tube above the waterline.

When lowering the float does not work

Lift the float (or cup) all the way up by hand and hold it.

Water stops: the valve works, the float just needed more adjustment, or it is rubbing the tank wall or the flapper chain. Make sure it moves freely.
Water keeps flowing: the fill valve is not sealing. Grit after a water shutoff or plumbing work is a common cause. Try flushing debris out of the fill valve first.
Still flowing after cleaning: replace the fill valve. Turn off the supply valve at the floor, flush to empty the tank, and follow the kit instructions. Universal fill valves adjust to most tank heights. Note which side of the tank the valve sits on (left vs right tank hole).

Common mistakes

Replacing the flapper for an overflow problem. A new flapper will not stop water spilling over the top of the tube. See Toilet still runs after a new flapper.
Lowering the float too far. Water far below the line gives a weak flush. Stop at about ½ to 1 inch below the tube top.
Cutting or plugging the overflow tube. It protects against the tank spilling onto the floor. Never remove it or block it to quiet the toilet.
Bending a plastic float arm. It can crack. Use the adjustment screw.
Forgetting to check after the next few flushes. Watch two or three refills before you call it fixed.

Overflow tube FAQ

Why is water running into my toilet overflow tube?

Either the water level is set higher than the top of the tube, or the fill valve is not closing. Lower the float first. If holding the float up does not stop the water, the fill valve needs cleaning or replacement.

Is it normal for water to go down the overflow tube?

A small stream from the refill tube during refilling is normal, because that is how the bowl refills. Water spilling over the tube’s rim after the tank is full is not normal.

How far below the overflow tube should toilet water be?

About ½ to 1 inch below the top, or at the water line mark on the tank or fill valve if there is one.

Does water in the overflow tube waste water?

Yes. A fill valve that never shuts off can run water straight down the overflow into the bowl all day, which shows up on the water bill. That is worth fixing quickly.

What if the overflow tube itself is cracked or too short?

A crack below the waterline lets water drain into the bowl constantly, and that means replacing the flush valve, which is a bigger repair. If you are not comfortable taking the tank off the bowl, call a plumber.

Why does my toilet run on its own every few minutes?

That is usually a slow flapper leak, not overflow. See Toilet ghost flushes or refills on its own.

Honest stop

Cracked tanks, water on the floor, or seepage at the base of the bowl are plumber jobs. This guide stays inside the tank.