Why Is My Toilet Water Level Low?

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You probably expect the toilet to work flawlessly forever, but sometimes it can surprise you with a low water level. You’ll know it as soon as you look at the bowl — the puddle you expect to see is not there. 

But why is the water level in your toilet so low? Many things can cause it — a crack in the bowl, damaged flappers and fill valves, or blocked air vents. Sometimes the shutoff valve is not open, while the tank float may also be too low.

The good thing is that most of these issues have a quick fix. Let us show you how to increase the water level in the toilet.

6 Causes of Low Toilet Water Level & How to Fix It

Homeowners who want to increase the water level in the bowl must discover the root of the problem. It usually comes down to these five issues.

1. Cracks in the Toilet Bowl

Toilet bowls consist of porcelain, a durable material that can last for decades. But porcelain is also fragile, particularly when you hit it with a hard object. In this case, it can crack and start losing water.

Cracks in the toilet bowl can cause some serious leaking at the base. You’ll soon notice an unusual puddle on the floor, which indicates that you have a plumbing problem.

Solution: Replace the Toilet Bowl

Replacing a toilet bowl is the hardest of our solutions, but don’t let that discourage you — it only takes an hour or two to change the cracked item. We prepared a series of instructions on how to do it properly.

Close the water supply by twisting the shutoff valve clockwise. Use WD-40 to loosen the knob if the shutoff valve won’t shut off. After that, you can remove the supply hose that connects to the toilet tank.

Do it by unscrewing the threaded nut holding the hose on the tank bottom. Now you are free to flush the toilet and empty the tank, while the next step is to detach the tank itself.

After that, use a small cup and a dry sponge to remove the excess water from the bowl. Pour excess water in the bucket and dry the bowl thoroughly by wiping it with the sponge. 

Then, you can unscrew the toilet bolts – turn them counterclockwise with pliers until they fall out of the base. The bolts were holding the toilet bowl, so you can now remove it with your hands.

Now you can set up the new toilet bowl. 

Now you can set up the new toilet bowl. Put it on the floor to cover the outlet drain, but remember to tighten it with a pair of bolts. After that, reinstall other parts one by one — the water supply hose and the tank. Finally, you can open the shutoff valve.

2. Toilet Tank Is Not Filling

Sometimes the water level is low because the toilet tank is not filling. Without enough water in the tank, the pressure is too weak to fill the bowl and push out the waste from it.

The cause of the problem is likely a damaged toilet flapper.

Solution 1: Replace the Toilet Flapper

When you notice that the tank is not filling, you should put on rubber gloves and check the toilet flapper. This part is connected to a chain — it is responsible for preventing an overflow of water. 

Flappers wear out and start leaking over time, but you can replace them quickly.

Close the water supply by turning off the shutoff valve. This allows you to empty the tank – flush it and remove the lid afterward. Check the tank to find the toilet flapper at the bottom — it’s a round rubber or plastic part below the overflow tube.

Detach the flapper with your hands, so you can insert a new flapper by snapping it on the outlet pipe. Seal it tightly with your fingers, but don’t move other parts like the overflow tube or the float arm. 

Finally, you can close the toilet tank with the cover and open the supply line.

Solution 2: Replace the Fill Valve

The fill valve is an inlet valve that’s responsible for filling the tank with water. When it’s not working, the tank can’t receive enough water to clean the bowl. The result is the weak flush power and the low water level in the toilet bowl. 

Fortunately, you can replace the fill valve with ease. 

Firstly, close the water by turning off the shutoff valve. It’s the only way to empty the tank, so you can now flush the toilet and remove the tank lid. It’s easy to find the valve on the left side of the tank — this part is next to the overflow tube.

The fill valve is the tallest element in toilet tank mechanisms, but you can lift it easily as it’s lightweight. After that, insert the new fill valve by placing it on its base. Another step is to close the tank with the lid and turn on the water supply.

When you do all that, flush the toilet to reset the toilet bowl water level. 

3. Blocked Air Vent

The air vent is a long pipe that transfers the air from the roof to the sewer drains. That way, plumbing vents balance the pressure in the waste pipes, helping your toilet work normally.

However, the entrance to the vent pipes sometimes clogs because it’s on the roof — leaves may fall into it, and birds may build nests there. When this happens, there is no air pressure to push clean water back into the ball.

Solution: Unclog the Air Vent

The solution is to unclog the plumbing vents. You must climb the roof to clean vent pipes, but remember to secure yourself with ropes and standing platforms. After that, follow these steps:

  • Use a garden hose to clean the vent with water — it may be enough to break debris
  • If the water backflows, use a toilet auger to break the clogs. Push the tool inside and let it break hard waste with its sharp tip
  • Now you can use the hose again to remove the last waste remnants

After doing this, the pressure in the plumbing system will restore. The flush system will function well, so you will see a normal water level in the bowl.

4. The Tank Float Is Too Low

The tank float is a device that controls the water level in the toilet tank. It’s a black ball with a metal rod, which connects to the fill valve. When the float is high, water flows into the tank freely. If not, the water level is low.

Solution: Lift the Tank Float

The good thing is that you can adjust the tank float with ease. You only need to raise the float ball until it reaches the desired water level. It’s unnecessary to close the water because you’ll see the float on top of the tank. 

Put on a pair of rubber gloves and remove the tank cover. Now you can identify the metal float arm — it’s a long rod that holds the float ball. A small screw connects the rod to the fill valve, so you need to unscrew it. 

That allows the float to move up and down, which means you can raise the float until it reaches the desired position. Now you can screw the bolt to secure the float and close the tank.

Ideally, your tank float will stay a couple of inches below the tank lid. That’s enough to fill the tank with two gallons of water, so it can fill the toilet bowl, too.

5. The Shutoff Valve Is Not Fully Open

We mentioned the shutoff valve many times before. The little knob behind the toilet allows or stops the water flow, so it can impact the water level in your bowl.

When the shutoff valve is not entirely open, the flow is too weak to fill the tank and the bowl. But the good news is that opening the valve is very simple, so let us explain the whole process.

Solution: Open the Shutoff Valve

You will find the shutoff valve on the wall behind the toilet or next to it. Twist the shutoff valve counterclockwise until it goes a full circle — it will open the water supply line to the fullest. 

If the knob on your valve is too stiff and doesn’t budge, remember to spray the valve with WD-40 penetrating oil. Try again after 10 minutes — the knob will turn easily, so you can open the valve.

6. Partial Clogs In the Trapway

Partial clogs in the trapway can also be a source of the problem. A partially clogged toilet drains slowly, but the siphoning effect continues after flushing. It’s how your toilet is trying to get rid of the clog by itself.   

But some clogs are too hard to allow the toilet to unclog itself eventually. In this case, you’ll need to remove a partial clog the hard way. 

Solution: Unclog the Trapway

Our suggestion is to wear gloves and try to break a clog with your hands. The clog is probably in the toilet trap, so you can reach it with your fingers. If you don’t like this solution, a toilet plunger will help for sure.

Use this tool to break the clog with brute force. The plunger goes into the bowl and seals the outlet drain with its rubber base. After that, you need to pump it up and down to create a lot of pressure.

You’ll know the pressure is high when the plunger stops moving – it’s a sign that you must pull and detach the plunger. The pressure it creates should be enough to dissolve the clog and send it down the drain.

The Consequences of the Low Water Level in the Toilet

Do you know why it’s important to adjust the water level in the toilet? We can give you several hints.

Firstly, the toilet can’t flush strongly because it doesn’t have enough water. A low water level in the bowl makes the toilet flush less effective, as there is no pressure behind it. You can’t dispose of waste, and poop will stick to the bowl.

Secondly, bacteria and germs will breed in the bowl. Some of it will stay on the rim, causing disgusting smells. In this case, event the best exhaust fans won’t help you refresh the bathroom.

Even worse, your toilet may overflow due to excess waste that can’t go through the bowl. It’s the worst-case scenario, so you better act quickly to prevent it.

The Bottom Line

We just covered the most common reasons causing a low water level in the toilet bowl. It usually comes down to these causes:

  • Cracked toilet bowls
  • Faulty position of the tank float
  • Broken fill valve or toilet flapper
  • A partial clog in the air vent
  • A shutoff valve is not fully open

If you see a lower water level in your toilet, look for the cause. After that, our instructions will help you resolve the problem very quickly.


What causes the water level in the toilet bowl to drop?

The water level in your toilet bowl may drop for several reasons, but the cracks are the most common cause. Besides that, toilets may suffer from broken fill valves or flappers.

Sometimes the shutoff valve is not fully open, preventing the water from entering the tank. Finally, plumbing vents may clog and stop the toilet from working adequately.

What happens if the toilet water level is too low?

If the water level is too low, your toilet can’t flush strongly. It can’t dispose of waste, so you’ll probably find an ugly scene in the bowl. Besides that, the bathroom will get an awful poop and urine smell.

Why is my toilet bowl not filling with water after the flush?

A clogged air vent is likely the reason why your toilet bowl is not filling with water after flushing. The air vent is a pipe with an opening on the roof. Its purpose is to allow air into the outlet drain.

The air vent breaks a vacuum seal that stays in the drain after flushing. A clogged air drain can’t break the vacuum, so the water doesn’t return to the toilet bowl. The solution is to unclog the vent with a toilet auger.

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