Why Does The Water Level In The Toilet Bowl Drop?

Without enough water in the toilet bowl, its function is reduced or diminished entirely. You might be unable to use the toilet at all, especially if the water level is too low to effectively remove waste from the bowl. If the malfunctioning toilet is the only one in your household, the lack of bathroom facilities can be problematic.

Key Points:

  • Low water levels in the toilet bowl can be caused by a crack in the bowl, a clogged vent pipe, or an obstructed vent system.
  • To determine the cause of the low water levels, one may need to turn on nearby faucets to listen for gurgling noises, which indicates an issue with the vent.
  • Fixes for these issues include DIY cleaner work or professional help, such as replacing the toilet or having a plumber clean out and secure the vent pipes.

So, what causes this irritating issue? It can be a variety of things, including issues with the vent stack or problems with the flapper valve. This guide explains the common culprits and how to remedy the situation, so continue reading to learn more!

What Causes The Water Level In The Toilet Bowl To Drop?

Low water levels in toilet bowls are a relatively common issue. In some cases, the problem is straightforward, but in others, the issue is more complex. Here are a few of the most common causes and how to fix them:

Cracked Toilet Bowl

While toilets are often made of durable porcelain, they can occasionally break. While the break might be minor, like a barely visible (or invisible) hairline crack in the bowl, it can cause issues. If there’s a crack, even a small one, in the toilet bowl, the water level in the bowl may constantly remain low as water leaks out.

You can test this theory by filling the toilet bowl to its normal level with the water. Mark the spot with a non-permanent marker. Wait a few hours, then check the water level in the bowl. If the water level has dropped without any other drains in your house being used, the toilet likely has a small crack.

How To Fix It

Unfortunately, cracks in your toilet bowl aren’t usually fixable. So, you’ll need to replace the entire toilet in most scenarios. If you’re familiar with these projects, you can replace the toilet yourself. You’ll probably need an extra hand to lift the toilet into place (they’re heavy!), but the process is relatively straightforward.

Otherwise, you can hire a plumber to replace the toilet for you. On average, hiring a plumber to replace your toilet costs between $210 and $700. The fluctuation in pricing is due to the variability in labor costs and toilet prices.

Vent Clogs

For your toilet to function correctly, it requires an unobstructed vent system. If there’s something blocking the vent, there won’t be enough air to refill the toilet bowl. When the toilet operates normally, the water creates a vacuum seal in the drain. The vent allows air in to correct and balance the negative pressure.

However, if the vent is obstructed, the vacuum will remain, as there isn’t enough air to fill it and pull fresh water into the toilet bowl. So, if the vent isn’t working properly, neither will your toilet. It will likely be unable to remove waste from the toilet when you flush, as there isn’t enough water pulling into the bowl.

You can test for this issue by turning on the faucets in your home and listening closely to the sound of the water. If you hear a gurgling sound, the vent is probably the culprit. The gurgling noise stems from the drains as they draw air through your toilet.

How To Fix It

If the vent is the problem, you’ll need to clean it. In many cases, unwanted visitors, such as birds building nests within the vent, will block the vent atop your home. If you’re comfortable doing so, carefully climb up to the vent and use a wire hook or metal coat hanger (bent to form a hook) to lift the gunk out of the vent.

Alternatively, you can hire a plumber to handle the problem. If you go this route, you can expect to pay between $100 and $200, the average cost for professional vent cleaning.

After cleaning the vent, you can ask the professional who handles the job about preventative measures. They may recommend using an open cover or screen over the end of the pipe, as this will prevent gunk from entering the vent pipes (and unwanted visitors) without obstructing airflow.

If you try removing the obstruction on your own and are unable to remedy the issue, it’s usually better to hire a professional. Since vent stacks usually sit atop the roof, attempting to use tools up there without proper protective equipment can be dangerous. So, if your efforts to remove the clog are fruitless, consider hiring a plumber.

Fill Tube Issues

Inside toilet tanks, there’s a plastic hose that regulates the water level in the system. This tube, called a fill tube, refills your toilet with water after each flush. If the fill tube is damaged, it’ll be unable to refill the toilet after each flush.

If there isn’t enough water in the tank to refill the toilet bowl, you’ll notice the water in the bowl will continually drop. Or, after you flush the toilet, the water level will drop after whisking away the bowl’s contents, but it won’t refill.

How To Fix It

If the fill valve is the culprit, you’ll need to replace it. Here’s what you’ll need for this project:

  • Sponge or rag
  • Bucket
  • Adjustable pliers
  • Replacement fill tube

Once you gather the necessary materials, follow these steps:

  1. Turn off the water supply to your toilet.
  2. Flush the toilet a few times until the excess water from the bowl and tank drains out.
  3. Remove excess water from the tank using a sponge and a bucket. Soak up the water with the sponge, wring the water out into a bucket, and repeat the process until the tank is empty.
  4. Carefully pull the ball float out of the tank and set it aside.
  5. Locate the plastic nut attached at the middle of the bottom of the tank. Use a pair of adjustable pliers to remove it gently.
  6. Find the fill tube, which will be off to one side near the supply line. Gently remove it from the tank.
  7. Replace the old fill tube with the new one. Tighten the valve nut to secure it in its place.
  8. Reinstall the plastic nut in its place in the base of the tank and tighten it firmly, but don’t overtighten it.
  9. Replace the ball float in the tank, turn the water back on, and check your handiwork.

Damaged Seals

At the base of your toilet, a water-tight seal prevents the toilet from leaking out of the bottom. This seal, better known as a wax bowl ring, can cause issues when dislodged. So, this wax ring might have popped open if your toilet was rocked back and forth or jarred out of place. Generally, this happens when the flange bolts at the bottom of your toilet are too loose.

The wax ring can affect the amount of water that flows into the bowl. If the wax ring is compromised, it could cause the bowl to fill with less water than it needs or drop intermittently. If this is the case, you’ll usually find signs of water leaking from underneath the toilet. So, check around the toilet’s base for water damage or pooling.

How To Fix It

Unfortunately, repairing a damaged wax seal requires the removal of the toilet. You’ll need to remove the toilet from the flange and replace the wax bowl ring. If you’re familiar with the ins and outs of plumbing-related projects, this will probably be a breeze for you.

However, if you’re unfamiliar with plumbing issues, it’s usually best to outsource this project to a professional. On average, hiring a plumber to complete this task costs between $90 and $120, although it may be higher or lower in certain areas.

Flapper Valve Problems

The flapper valve is the circular valve at the bottom of the toilet tank. When you flush the toilet, the valve opens to drain water from the tank into the empty toilet bowl.

If the valve is damaged or not seated properly, the toilet tank won’t be able to fill up, causing the toilet to continue running. In addition, the water level may remain low as the toilet bowl constantly fills and empties with water.

You can use food coloring to determine whether the flapper valve is the issue. Remove the lid from the toilet tank and carefully set it aside. Add a few drops of food coloring to the back of the toilet tank. If the water flowing into the tank is colored, there’s an issue with the flapper valve.

How To Fix It

If the flapper valve is the culprit behind the issue, you’ll need to replace the flapper valve. This process is simple, but you’ll need a replacement flapper valve before starting. When you’re ready, follow these steps:

  1. Turn off the water at the shut-off valve on the intake pipe. This should be connected to the hose leading from the toilet tank, connecting to the wall or floor next to the toilet.
  2. Flush the toilet to drain excess water.
  3. Lift the flapper valve from the tank by disconnecting the chain hook.
  4. Install the replacement valve and position the flapper in place.
  5. Turn the water back on and check for proper function.

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