What Causes Water Level in a Toilet Bowl to Drop?
There is always water at the bottom of the toilet bowl, something made possible by the S-shaped toilet trap.
The water at the bottom of the toilet bowl creates a barrier between the drain line and the toilet, preventing sewer gases from coming up to the bathroom. It also helps your toilet to flush better.
Depending on your toilet model, the level of water inside the bowl is supposed to be at a certain point, unless there is a problem with the toilet.
Low water level in a toilet bowl is a sign that the tank refill tube is damaged or not properly attached to the overflow tube. It could also be caused by low water level in the tank or a hairline crack in the bowl.
In rare occasions, low water level in a toilet bowl can be caused by a clogged plumbing vent. When that is the case, the water in the bowl is sucked inside the drain line when another fixture is draining due to the creation of negative air pressure in the drainage system.
To raise the water level in a toilet bowl, make sure that the tank refill tube is not damaged and that it is properly positioned inside the overflow tube. Also, adjust the water level in the tank to just an inch below the overflow tube. If the bowl is cracked replace it.
If you notice that the toilet bowl does not fill up after flushing, either the tank refill tube is damaged, or it is disconnected from the overflow tube. Usually, the refill tube should fill the bowl via the overflow tube as the fill valve is refilling the tank.
If the water level in a toilet bowl is dropping, you could be having a hairline crack in your bowl or the refill tube could be so deep inside the overflow tube and thereby siphoning water from the bowl. A clogged plumbing vent could also result in negative air pressure and suction of water from the toilet bowl.
How to Fix Low Water Level in a Toilet Bowl
The good thing is that in most of the times, fixing low water level in a toilet bowl is easy and fast. You will rarely need to enlist the services of a plumber.
The following are the different ways to fix low water level in a toilet bowl:
1. Fix the Refill Tube
There are 2 cycles involved when using a toilet. These are the flushing cycle and the filling cycle. The problem we have here falls in the filling cycle.
After flushing the toilet, the toilet fill valve opens and starts filling the tank with water in readiness for the next flush.
There is usually a thin (mostly black) tube connected from the fill valve to the overflow tube. This tube is called the refill tube.
As the fill valve is filling the tank, the refill tube sends a little water down to the bowl via the overflow tube. The overflow tube is the large tube in the middle of the tank. It is connected to the flush valve.
If the refill tube is damaged or if it has disconnected from the overflow tube, no water will be sent down to the bowl after flushing. As a result, you will end up with low water level in the bowl.
Toilet tanks are different. In some, the refill tube is connected to the overflow tube using a clip while in others the tube is simply pushed down the overflow tube. Check what you have in your toilet.
Inspect the refill tube for cracks which means it could be leaking and therefore failing to fill the bowl. If it is damaged you will need to replace it.
Next, check if the refill tube has disconnected from the overflow tube. If it has, you will only need to connect it back and your problem will be over.
Another thing related to the refill tube that could be causing the bowl water level to be low is when the refill tube is inserted too deep inside the overflow tube.
When that is the case, the refill tube siphons water from the bowl and hence a low water level in the bowl.
If you notice that the refill tube is not damaged and it is properly connected to the overflow tube, pull it out and cut it out so that it just about 2 inches inside the overflow tube.
2. Adjust the Water Level in the Tank
What you may not know is that the water level in the tank also affects the water level in the bowl. If the water level in the tank is low, the water level in the bowl will be low as well.
Ideally, the water level in a toilet tank should be about ½ inch below the top of the overflow tube. Some tanks however have a mark for the correct water level.
Adjusting the water level in a tank is easy and fast. The first thing you will however need to check is whether you have a float ball or a float cup, also known as a float cylinder.
If you have a float ball, look for a screw where the float arm is connected to the fill valve. Use a screwdriver to turn the screw clockwise until you achieve the correct water level.
With a float cup, look for a long plastic screw alongside the vertical body of the fill valve. Again, turn the big screw clockwise to increase the water level in the tank.
After adjusting the water level in the tank, flush the toilet and check if the water level in the bowl has risen to the desired levels.
3. Look for Hairline Cracks
If when you flush the toilet the water level in the bowl is good but it drops after some time, you could be dealing with a cracked bowl. Some cracks are so hard to see with your naked eye (hairline cracks) but if you look carefully you can see them.
With a cracked bowl, the water can pool around the base of the toilet or it can flow down to the drain line depending on the location of the crack.
In other instances, the water can flow to the ceiling of the floor below, which can be manifested by a stained or damp ceiling.
Unfortunately, a cracked toilet bowl cannot be fixed. If after examination you find out that your bowl is cracked, you will need to replace it with a new one.
For folks with a 2-piece toilet, you can opt to only replace the bowl but folks with a 1-piece toilet will need to replace the entire toilet.
4. Unclog the Plumbing Vent
Your toilet and other drains in the house are connected to the plumbing vent. A plumbing vent is the vertical pipe connected to the main house drain stack and which runs through the roof of the house.
The 2 main functions of the plumbing vent is to introduce air into the drainage system for fast drainage and to also remove sewer gases from the system.
When, a plumbing vent is clogged (by leaves, balls, dead birds or rodents, snow etc.), sewer gases will not exit and fresh air will not be introduced into the drainage system.
With a clogged plumbing vent, all drains will be affected and not just the toilet. Some of the signs of a clogged plumbing vent include:
- Slow drains
- Weak flushing toilets
- Gurgling drains
- Bubbling toilet
- Sewer smell in the house
So, how does a clogged vent stack result in low water level in a toilet bowl?
When a vent is clogged and then you drain the bathtub, sink or washing machine, negative air pressure builds up inside the drain line. In simple terms means that a vacuum is created inside the drain line.
As a result, the water in the bowl is siphoned out to balance the air pressure and hence the low water in the toilet bowl.
To unclog a plumbing vent, climb to the roof of the house, a garden hose in hand. Use the hose to break down the clog then have someone turn on the water to the garden hose and hope that the weight of the water is enough to wash down the clog.
If the clog won’t budge, upgrade to a plumber’s snake. A snake will definitely clear the clog.
And basically that is how fix low water level in a toilet bowl. I hope this guide was helpful.