Common Problems with Toilet Cistern

The toilet has two parts, upper and lower, and each has distinct functions. The upper part is the cistern, while the lower is the bowl with seat fixings. The cistern is a larger part with a tank-like structure for water storage.

Common problems with toilet cistern include cracking, improper flushing, faulty ball valve, worn out washer seal, condensation on the outer surface, and faulty float valve. Moreover, the issue also comes due to a defective float arm, poor adjustment of the float arm, leaking, and damaged buttons. 

The primary function of the cistern is to flush the water in the bowl to remove solid waste from it. These contain push buttons and automatic sensors for the movement of water.

Toilet Cistern Problems Solutions
Cracking Apply sealant
Improper flushing Flush out the plumbing system to remove lime
Worn-out washer seal Perform food coloring test
Condensation on the outer surface Turn on humidifier
Faulty diaphragm valve Replace diaphragm assembly
Algae and dust on the walls of the cistern Wash with bleach
Leakage of cistern Seal the sidewalls


Toilet water tanks or cisterns are mostly made of high-quality plastic material. In addition, most of them are highly durable and made of concentrate and fiberglass material.

The mixture of fiberglass and concrete material is more resistant to cracks than plastics. As a result, these tanks last longer, and there are no significant cracks in their structure.

The hairline cracks come on their exterior layer due to age and stress. In addition, people often put heavy objects on their surfaces which can produce hairline cracks.

Those made up of fiberglass or concrete material cannot crack or scratch easily. However, you can also see small lines on the surface of plastic ones because of using the wrong type of detergent.

Harsh detergents for a long time damage the plastic material and cause drying of their components. These can crack easily due to the drying of plasticizers and other parts.

It is not necessary to replace the cisterns to fix the cracking issue. These are primarily hairline cracks, and you can easily seal them with a tape of sealants.

Moreover, you can also use wood or plumber’s putty to secure the hairline marks. Keep them dry for at least one day after applying the sealing material.

Improper flushing

Many times, people face the issue of improper flushing after getting free. The improper flushing occurs due to faulty cistern tanks.

The issue comes when the water level in the tanks is low, and there is no sufficient water for flushing. The water level becomes low when there is an issue in the plumbing system.

Sometimes the plumbing system that supplies water to these tanks becomes clogged and restricts the supply.

The slow filling and decreased water level cause this problem. The calcium builds up in the plumbing system, and the tank takes longer to fill at its required level.

You can resolve the problem by checking the clogged plumbing system connected to toilet cisterns.

Moreover, I prefer to flush out the plumbing system with a mixture of bleach and warm water to wash out the clogged particles and lime accumulation.

Worn-out washer seal

The worn-out washer seals or pressure make the toilet water tank faulty and cause slow water dripping.

Continuous water dripping in the bowl is due to these faulty seals. These seals are also known as gaskets made of neoprene plastic material.

These are vulnerable to wear and tear when the neoprene plastic becomes old. In addition, the degradation of neoprene plastic gaskets also comes due to corrosion.

The worn-out flapper or washer seal cannot control the outflow of water from the boundaries of the tank.

These are located on the upper and bottom boundaries for proper sealing and to prevent water from dripping into the bowl.

The wear and tear of washer seals come from the buildup of grimy material on their surface. Moreover, algae and molds also grow on washer seals, making them faulty.

You can perform a food coloring test to test the worn-out washer seal and water leakage. For example, you can use blue dye and add a few drops to detect leakage.

Condensation on the outer surface

Sometimes you can see water droplets on the tanks’ cistern, which is irritating for people when they sit on toilet seats.

It is problematic in winter when your cloth becomes wet due to condensation in the tanks.

The water in the cisterns is cold, and when the dry and hot air comes in contact with a cold surface, it produces water droplets on them.

Condensation occurs due to a mixture of warm and cold surfaces of the tanks. You can reduce condensation by maintaining the inner temperature and contact with warm air.

Keep the air vents open and turn on the ventilation fans for better air circulation. In addition, you can also put a dehumidifier in your bathrooms to get rid of condensation problems.

Faulty diaphragm valve

The Diaphragm assembly in the cistern works with the siphon tube for water flow. The primary function of this assembly is to create the siphon to draw water from the tank and flush it into toilets.

It contains a plastic seal to stop the water flow after proper flushing. The damaged seal of the diaphragm valve causes constant water to run in a bowl.

You can constantly hear the sound of running water from your bathrooms. The plastic seals are vulnerable to age-related wear and tear due to their flexible material.

These wear out due to their over and frequent usage in the long term. Moreover, plastic seals are also vulnerable to warping due to long-term use.

It is necessary to check the diaphragm assembly when you hear the sound of running water the whole night. Open the lid of the cisterns and replace the diaphragm valve with a new one.

Algae and dust on the walls of the cistern

Algae or fungus growth is a common issue in cistern walls and boundaries. The hot and humid environment is the most favorable place for the growth of these species.

The inner side remains humid due to water storage, and you can see green fungus on their sides. The fungus damages its internal component and affects the washer seal and diaphragm valve.

The fungus in water also comes from your tank and the plumbing system.

The accumulated fungus on the walls of tanks makes the water filthy and can damage the bowl when it moves through it.

You have to get rid of the fungus accumulation from the walls. Open the lid of the tank and wash it with bleaching agents.

Moreover, you can also use vinegar because strong acids cause the degradation of fungus species.

Leakage of cistern

Sometimes toilet cistern becomes leaky from their binding sides and side walls.

The side walls are bound with adhesive materials and sealants to keep them in their place and maintain proper contact.

The seals start to lose their adhesiveness over time and long-term water exposure. As a result, you can often see dripping water from its binding corners or lower ends.

Moreover, water can decrease the binding ability of the sealant material by breaking its bonds. It is common in side walls because of their poor sealing.

You can fix it by resealing the sidewalls and bottom ends. Use the sealing agent to fill the small and invisible gaps between the joining point of the walls.

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