Toilet Bowl Water Level Drops Overnight

Many people complain the bowl’s water level decreases overnight and becomes less than its original range. The low levels do not help keep the sewer gasses down and increase the risks of smell from the bathrooms.

Toilet bowl water level drops overnight because of leakage in a bowl, poor installation, failure of wax rings, high windy conditions, and clogged vents. Moreover, it happens when you have pets in homes, damaged flush valves, blocked inlet holes, and non-flushable items in drains. 

A sufficient amount of water is necessary on the lower side of the bowl because of its high gravity to keep the sewer gasses down.

Causes Solutions
Leakage in bowl material Treat cracks with porcelain epoxy
Poor installation Hire plumber
Failure of the wax ring Replace wax seal
High wind conditions Cover the vent pipes
Clogged vents Regular cleaning of vents
Pets Keep the lids closed
Damaged flush valve and blocked inlet hose Perform food coloring test
Adding non-flushable items Remove items with a plumbing snake and wire

Leakage in toilet bowl

The bowl material is made of porcelain and is susceptible to cracks because of its delicate and less durable materials. The deep cracks can cause the water to seep into the bathroom floors and make them unclean.

Porcelain is not a durable material, and it can develop cracks with age because of a damaged exterior glazing layer. In addition, the issue also comes when you use hard metal wire and cleaners to remove the clog from the drains.

Overtightening of nuts and bolts and mishandling during installation produce creaks on their surface. The internal creaks near the water levels are more dangerous and cause leaking.

You can identify the problem from the flooded surrounding floors. Inspect their nuts and slightly loosen them if you hear squeaking while sitting on the toilet seats.

Use porcelain epoxy to seal the internal cracks.

Poor installation

The wax seals are located on the floors, and you have to install the toilet flange on them to properly seal and prevent water from seeping into the surrounding floors.

People often install the toilets by themselves at home and do not take help from an expert plumbing expert. As a result, you cannot install them perfectly because of your less experience and knowledge.

The issue comes when you place the flange on the wax seals imperfectly. The smaller gap and imperfection lead to a seeping problem.

You can see contaminated water on the floors, which allows bacterial and mold growth. In addition, the issue also comes when you do not use the seal of the correct size.

The standing moisture can also cause degradation and rotting of subfloors. Replace the wax rings and calling the plumber for their correct installation is the best solution to resolve the problems.

Failure of the wax ring

The wax ring of the toilets loses its seals over time and causes water to leak from the bowl. In addition, the seals can get damaged when they are not thick enough according to the height of the flange.

In addition, the problem also comes when toilets are loose and are not installed correctly. The wobbling movement can damage the seals.

Moreover, you can also face this because of the cracking of rubber material. Rubber materials are less durable and can easily crack when you do not place the flange on them.

These toilets are fitted on the seals with the caulking and sealing material. Therefore, replacing damaged or cracked wax seals with new ones is better.

You can reseal them by taking help from the plumber and placing the toilets on the side carefully.

High wind conditions

It is confusing for some people how high winds decrease the water level in the bowl. It does not make sense because the wind is outside, and water is inside these toilets.

High wind conditions disturb the air pressure in the pipes. The moving air inside the pipes keeps the negative pressure, and you can see the low levels than their normal range.

The problem occurs when vent pipes do not contain any covers and these are damaged. The windy conditions affect the air pressure through the uncovered vent pipes.

Add the vent covers on the hoods so the outside environment cannot disturb the air pressure in the internal pipes.

Clogged vents

The plumbing system contains the roof vent pipes to remove the air from the drain lines. The primary purpose of a vent pipe is to exert negative pressure for the flushing mechanism.

The water and waste material move downward after flushing because of the negative forces. The clogged vents do not allow the unnecessary air to move outside, and it remains in the line of the bathroom fixtures.

The vent pipes are on the home’s roof, and dust, debris, leaves, and other foreign particles can accumulate on their opening points and block them.

Moreover, the issue also comes when snow accumulates on them in the winter. Inspect the vent pipes on your roof and keep them clean.

Use the covers to prevent the entry of foreign materials and contaminants. Regularly clean them and remove the snow from them during winter.


People keep pets in their houses for fun purposes and because of their hobbies. Some pets can also drink toilet water because they are not pickier.

Most commonly, dogs drink them when they cannot find the water in their containers. The levels in the bowl decrease when you forget to close the bathroom doors at night.

In addition, the issue also occurs when you do not fill the pots of your pets. These can also come there for drinking purposes when lids are not down.

You should keep the lids of the toilet seats down so pets cannot access them. Close the bathroom doors at night so no one can enter inside at night.

Damaged flush valve and blocked inlet hose 

The flush valve or flapper seal is the rubber item that allows the water movement into the bowl when you press the flush handle of the tank.

Sometimes the flapper seal can get damaged and does not allow a sufficient amount to move in the toilets. The same issue comes from the blocked inlet hoses, which restrict the supply.

You cannot get enough water in the p-trap area if the flush valve is damaged and the inlet holes are clogged.

Algae growth, cracked rubber seals, and mineral deposits affect the functioning of the flush valve. Moreover, the bacterial colonies and sediments clog the inlet hoses.

You can perform the food coloring test to inspect the flapper seal’s functioning. Use the toothpick and thin wires to unclog the inlet hoses.

Adding non-flushable items

Many people add non-flushable items to the bowl and press the tank handle for flushing. Some of these items are non-breakable and cannot move into the drains.

These non-flushable items include hair, diapers, thick tissues, baby wipes, Q-tips, cigarettes, and small toys.

These items clog the drains and produce siphoning action, draining water from the bowl overnight and decreasing their levels.

Moreover, the issue comes because tissues, cotton balls, diapers, and cigarettes absorb moisture when they remain there and start to swell.

Avoid flushing these non-breakable items that can lodge the pipes. Instead, you can take them outside with metal wires, old hangers, and drills if you accidentally throw them inside.

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