Why is Your Toilet Bowl Empty? Common Reasons and How to Fix Them4 min read

By design, your toilet tank and bowl should fill up with water to prepare for the next flush. However, if the tank isn’t working properly, the toilet bowl can run dry — and the toilet won’t be up to its normal task. So, what should you do if your toilet bowl is empty?

Check that your toilet’s tank is full and that there are no leaks from the tank or around the plumbing joints. Flush the toilet and open your bathroom faucets to send water through the drain. Pay attention to gurgling; it may indicate venting issues. Lastly, test the water level in the bowl.

A toilet that isn’t staying full is no one’s cup of tea. But it happens every now and then, so let’s take a closer look at how to deal with the issue and why it occurs.

Bowl on strike? here’s Why Your Toilet Bowl is Empty

Here’s why your toilet bowl may be running empty:

Venting Issues: diagnose and fix

Plumbing vents (sewer vent pipes) allow sewer gases to escape the waste pipes while also letting in the fresh air. But if your plumbing vent pipe is blocked, the pipes will want to access air from other outlets within your home, and they may suction the water from the toilet bowl.

In another article I wrote, I explain why vents are needed in the home plumbing system.

Water typically goes down the drain pipe that connects to the toilet bowl, but, in this case, it can’t happen because air won’t enter the vent pipe. Due to the powerful suction force in the sewer system, water will be sucked out of the toilet trap and down the drain pipe. Your toilet is effectively acting as a vent for the system.

You’ll notice this when your toilet makes loud gurgling noises as water and air get siphoned through your toilet bowl.

More often, the blockage occurs on the roof of your house, where the vent pipe is typically located. Anything from bird nests and dead birds to foliage on a windy day can block the vent pipe.

Other telltale signs of a blocked vent include:

  • Sounds coming from the bathtub or other sinks when the toilet is flushed
  • Sewage (Rotten egg) smell in bathroom/kitchen or near drains
  • Gurgling toilet and drains
  • Sluggish drains

how to clear a clogged plumbing vent

Note: If you don’t feel comfortable getting onto your roof or carrying out this sort of work, I’d highly recommend contracting a professional.

To clear a clogged plumbing vent you’ll need to climb onto the roof and remove any debris from the pipe. You should use a plumbers snake to clear blockages and wash it down to make sure using a garden hose. It’s good to invest in a vent cover afterward.

You can test whether the vent has been cleared by placing your hand over the top of the vent and asking an assistant to flush the toilet. If you don’t feel suction, there’s probably still a blockage.

I found this useful video that demonstrates how to clear a blocked vent:

Clog Issue 

A partial clog in your toilet’s plumbing causes water to be siphoned from the bowl, leading to low water levels. You can tell if you’re dealing with a partial clog by watching how the toilet flushes. If the water level rises in the bowl only to slowly go down until the bowl is dry, there’s back-siphoning somewhere in the trap of your toilet.

Your toilet trap is the curving channel behind the toilet bowl that connects the hole at its base to the drainpipe. It travels upwards, and its shape plays a crucial role in ensuring it maintains its functionality.

Toilet Trap
You can see the trap in my toilet here

When you flush your toilet, the last bit of water traveling down the drain stays in the trap by design. This residual water is important because it plugs the drain pipe to prevent horribly smelling waste gasses from traveling back into your house. 

But if there’s a partial clog in the trap, it can’t collect water, and your toilet bowl will run empty.

You can try removing the blockage at the trap using a plunger. Here’s an article that explains a few other methods to remove blockages, and worst case you can remove the toilet bowl itself to access the trap.

If the issue persists, however, you’ll have to consult a plumber. They’ll use a device called a closet auger, which is more effective and efficient at removing blockage from the trap.

Clogged Inlet Holes

Another reason for abnormally low water levels in your toilet bowl is clogged inlet holes. These inlet holes, or rim jets, are found just under the rim of your toilet. 

Depending on the type of toilet and the quality of your tap water, it’s possible that hard water mineral deposits can build up and plug the holes.

To fix clogged inlet holes, start by carefully pouring hot vinegar into the tank through the overflow tube. Let it sit in the tank for a couple of hours to dissolve hard water mineral deposits. Use a hard-bristled brush to scrub away residual deposits from the tank.

Poke a small stiff wire inside the rim jet holes and carefully run it up and down to clear any debris inside the holes. Flush the toilet once you’re done to see if this fixes the problem.

How to Figure Out Why Your Toilet Bowl Is Dry 

To figure out why your toilet bowl is dry, it’s important you first ensure the water supply to your bathroom isn’t compromised and that the pipe connecting it to the bowl is firmly sealed. This will help you narrow down the source of the problem. 

You also want to check if something has accidentally triggered the shut-off valve. But if the shut-off valve is off and the water supply is running accordingly, proceed with these steps:

  1. Check That the Tank is Full

If there’s no water in your toilet’s tank, and the issues we’ve discussed above are also in play, the bowl will easily run dry. Carefully lift the lid of the tank to check if there’s enough water in it. 

You can also tap the tank gently to check if it’s full. It shouldn’t produce a hollow sound if there’s enough water in it.

  1. Send Water Through Your Bathroom Drains

Open your bathroom faucets to the maximum and let the water flow through the drain. This will help you figure out if the drain is clogged.

  1. Pay Attention to Gurgling

As the water flows through your bathroom drain, listen carefully to the sound it makes. If it’s gurgling heavily, the problem probably lies in your plumbing vent pipe.

  1. Test the Water Level

You’ll need your bathroom gloves for this troubleshooting step. Clean and flush your toilet bowl, then let it sit for 15 minutes. Mark the current water level on the porcelain and leave the toilet unattended for about an hour and a half. 

Draw a short line above the current water level with a waterproof marker and check it after one and a half hours. If the water level goes down while the faucets are off, it means the tank is leaking.

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Hi, I'm Ed, and I run BuildFanatic! I enjoy providing the best possible information on a range of home improvement topics.

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