How to Fix a Runny Toilet

A toilet that’s constantly running is a plumbing problem you will want to be addressed as soon as possible. A runny toilet will cause your water bill to soar and hundreds of gallons of water wasted daily. There could be several causes, from the toilet flapper malfunctioning to the toilet fill valve needing a replacement.

To fix a runny toilet, we have to look at all possible causes. Fortunately, most of these can be tackled by the homeowner. Of course, you also have the option to contact a plumber for professional assistance. Either way, you will want to address your runny toilet as soon as possible.

Here is a guide on how to fix a runny toilet:

1. Turn off the water and drain the toilet

Before tackling any toilet problems, turn off the water to the toilet and fully drain it. This will remove any excess water from the tank and allow you to inspect the toilet without water constantly being run.

2. Check the toilet flapper for problems

The most common cause of a runny toilet is a toilet flapper problem. The flapper is the round rubber seal that stops water from draining out of the tank and into the toilet bowl. The flapper’s installed on a chain and is pulled up to fill the bowl. Then, it falls downward, plugging water transfer. If it’s not doing its job, it needs to be fixed. To have a look, remove the toilet tank lid and set it down somewhere safe.

3. Adjust the chain length if it’s too short or long

The flapper chain may be too short and be pulling up on the valve when it shouldn’t. It could, alternatively, be too long and get caught underneath the flapper. This would not make it possible to seal the hole as the flapper designed. If the flapper chain’s too long, cut it with a pair of wire cutters and reattach with a few links trimmed.

4. Check the toilet flapper for damage

Unhook the sides from the pins at the bottom of the overflow tube and remove the flapper. If there are mineral deposits, you can clean them off. If there’s any warping, discoloration, or if the flapper’s outright broken, get a replacement.

Over time, a flapper may get brittle and hard and won’t seal correctly. A replacement is cheap and easy and should resolve any issue there.

5. Check the water level in your tank

Another source of a runny toilet could be the water level being too high. When this happens, water drains into the overflow tube. You can adjust the water level by lowering the float, which is located on the fill valve. The float height is what tells the fill valve to shut off. It’s a signifier that the toilet tank is full.

6. Grab a screwdriver to adjust the float

On top of your fill valve is a screw attaching the arm to the valve. Turn this screw with a screwdriver to adjust the height of the float. Turn the screw a quarter-turn counter-clockwise to lower the float.

Let the tank refill and check the water level. Where you want the water to be is 1-1.5 inches below the top of the overflow tube. You may need to adjust this a few times to get it right.

7. Check the fill tube for intermittent running

If your toilet is runny, not off and on, it could be the refill tube. This tube should be above the water line. When it’s not, that’s what causes the intermittent running. When the tank is full, the fill tube shouldn’t be in the water. To fix this, you can manually trim the tube, so it sits above the tank’s water line.

8. Replace the fill valve if it’s malfunctioning

You may need to replace the fill valve. To do this, you need to empty the tank and disconnect the water supply line. You may need a pair of pliers to loosen the locknut, turning it counter-clockwise to disconnect the supply line.

Next, remove the original fill valve. There will be another locknut attaching the fill valve assembly to the toilet on the outside of the tank. The fill valve assembly should pop right off. You can take this to the hardware store to ensure you get a replacement that’s the right size and style for the toilet.

If you have an older ball float fill valve, more modern float cup style fill valves can often be used as their replacement.

9. Install your new fill valve and connect the water

Installing the new fill valve is easy. It goes in the same place as the old one. Once it’s on, hook up the water supply line and tighten the nut. Attach the fill tube to the water output nozzle, ensuring it’s draining into the overflow tube as designed.

Check and adjust the float, if necessary. Turn the water back on and test the fill valve. Flush the toilet a few times and let it fill up again. In most cases, these are all the steps to fix a runny toilet.