Can a Toilet Fill Valve Cause Toilet to Run?

“Johnny, that dripping of my toilet is driving me crazy!” complained my next-door neighbor Phil. His toilet randomly runs for a few seconds. It’s actually a common problem that homeowners frequently face.

If left unattended, this on and off run and the accompanying sound can become a huge nuisance, as my friend found out the hard way. 

More often than not, this happens because the toilet fill valve keeps running. It was the case with Phil’s. But as you can see, I’ve got his back! To save you from similar inconvenience, I’ve covered the entire process of fixing a toilet with a runny fill valve in this article.

Toilet Fill Valve Cause Toilet to Run?

YES! That’s the short answer. The valve basically ensures that your toilet tank gets refilled after you flush your toilet.

If you’re using a conventional toilet, yours has a Ball-Cock fill valve. Its design is pretty straightforward: just a tube that houses a shutoff valve. Connected to a junction at the floor of the toilet tank, it controls the water level in the tank.

This ensures that a fixed amount of water is stored and released every time you flush.

The triggering mechanism for this process is an air-filled ball connected to the valve assembly. When the water level goes down, the floating ball or cup also gets lowered. A connecting rod opens the fill valve, and the water pours into the tank—the filling up stops once the water gets back to its original height.

If there’s a fault in the mechanism, let’s say a leak or something, the inevitable happens: the toilet runs randomly!

Why Does My Toilet Run Randomly?

Simple may it be; a fill valve can still run into three common problems. All of them can cause the valve to run on and off. The issues are – slow inflow, leakage near the fill line, and jamming of the float valve or the ballcock connecting rod.

1. Very Slow Pour

Sometimes, the water that comes through the fill valve comes very slowly. It’s common for the toilets used for many years or the ones left over for some time. This usually happens due to the build-up of molds and mildews in the pipe.

As a result, the channel becomes narrow, slowing down the flow. This irregularity of inflow can result in unpredictable discharge.

2. Fill-Line Leakage

Well, as I explained earlier, the base of the fill valve tube is connected to the bottom of the toilet tank. From there, it passes water to the water supply line. The joint between the tank outlet and the valve tube base is made water-tight by a gasket.

Due to corrosion or simple long-term pressure shrinkage, the gasket often deteriorates. In this case, water starts dripping down, usually around the fill line.

3. Float Valve Jamming

The fill valve is controlled either by a float valve or an air-filled ball or cup. When the water level goes down, the float valve or the ball drops, leaving the fill valve open to receive water through the fill line.

This process gets hindered when the float valve seizes up because of the calcium build-up. The same thing happens when the float ball connecting rod gets jammed due to rust or mildew. As a result, the toilet randomly runs.

How Do You Fix a Toilet Fill Valve That Keeps Running?

If you happen to spot any of the above three symptoms, it’s time for you to fix the fill valve. Pinpoint the exact problem before you start fixing it. The fill line leakage is the most easily identifiable one. For the other two: open the lead and see which jamming it is.

Step One – Adjusting or Fixing the Float Ball

To keep the water at the required level, you’ll either have to adjust the float ball. On top of the fill tube, there’s a screw that can be tightened or loosened to raise or lower the float ball. If it’s not there or jammed too tightly, you can just bend the connecting rod to fix the problem.

Step Two – Loosening Up the Float Valve

If the float valve gets jammed on the fill tube, you’ll have to take apart the fill valve assembly and clean it. Empty the tank by firstly flushing the toilet and then soaking up the rest of the water with a sponge. Remove the water supply line (fill line); it’s better to have a bucket while doing this.

Remove the nut and pull out the fill valve assembly. Then, remove the top cover of the assembly to take out the float valve. Clean the float valve off any debris, molds, etc. This will allow the float to move up and down along the fill tube easily. Make sure to clean up the gasket as well.

Final Step – Cleaning the Fill Tube

To clean up the fill tube, you’ll have to take out the fill assembly. So, follow the assembly removal process mentioned above. Once you’ve freed the assembly, pull out the tube.

Remove the strainer from the tube and rinse it under a faucet. You may brush it lightly to clean it further. Clean off the debris and molds inside the tube. Finally, put the strainer back inside the tube.

Final Words

Well, this is everything you need to know about how your toilet fill valve keeps running. Try to follow symptoms and pinpoint the exact problem of the fill valve. Then, apply the fix relevant to it.

And it’ll put an end to the random running issue once and for all. On top of that, you won’t have to spend that hundred bucks for the plumber!

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