4 signs your apartment’s water tank may be contaminated with bacteria

By Esther Amao 

The black plastic overhead water tank is a permanent feature in many homes. Because municipal public tap water is practically non-existent in most cities, households rely heavily on private boreholes or well water pumped into these high-rise tanks to serve daily domestic needs.

We use this stored water for bathing, washing cooking utensils, brushing our teeth, and sometimes even for drinking after basic filtering. However, because these tanks are usually perched high up on tank stands or roof slabs, out of sight truly becomes out of mind for many tenants and landlords.

Over time, dust, fallen leaves, bird droppings, and tiny insects creep inside through loose lids or broken pipe fittings. When raw borehole water sits trapped inside a warm plastic container under intense sunshine, it creates a perfect breeding ground for disease-causing germs.

According to water quality monitoring reports by health organizations like UNICEF Nigeria, consuming or washing with water contaminated by fecal bacteria such as E. coli remains a primary trigger for recurrent typhoid, severe diarrhea, and stubborn skin infections across urban communities.

In this article, Tribune Online examines four distinct physical signs that indicate your apartment’s water storage tank has been colonized by harmful bacteria, along with the step-by-step actions required to restore safe water flow.

Foul smell coming from your kitchen and bathroom taps

When you open your tap in the morning and immediately catch an earthy, musty, or rotten-egg odor, your water tank is sending an urgent distress signal.

Clean domestic water is naturally odorless. A strong, pungent smell usually means that organic matter such as dead lizards, trapped insects, or thick sludge at the bottom of the tank has begun to decay. Anaerobic bacteria feed on this rotting organic waste, releasing foul gases that mix directly into the water flowing down to your taps.

Ignoring this bad odor means your family is routinely washing with water heavily populated by bacterial colonies. The smell alone is proof that the natural microbial balance inside the storage container has broken down completely.

Murky, yellowish, or brownish discoloration in buckets

When you fetch water into a white bucket or washbasin and notice a cloudy, yellow, or muddy tint, the storage environment is seriously compromised.

Over months of pumping water, fine silt, iron rust, and mud particles carried up from the borehole gradually settle at the floor of the tank. As the layer of mud grows thicker, it creates a nutrient-rich environment where bacteria multiply rapidly.

Every time fresh water is pumped into the tank, the incoming pressure violently stirs up this toxic bottom mud, turning your tap water murky brown. Using discolored water to cook or wash dishes exposes your entire household to immediate gastrointestinal risks.

Slippery or slimy layer inside taps and bucket walls

If you run your fingers along the inner walls of your plastic water buckets or around the mouth of your bathroom tap and feel a slippery, greasy film, you are touching a living bacterial biofilm.

Biofilm is a glue-like layer created when microscopic bacteria adhere to wet surfaces and construct a protective shield around themselves. This layer allows colonies of bacteria and green algae to attach firmly to the plastic walls of your overhead tank and inside the delivery pipes.

Once a biofilm forms inside your water system, normal water flow cannot wash it away. It continuously releases fresh bacteria into every drop of water passing through the system, rendering ordinary washing soaps ineffective against contamination.

Unexplained recurrent typhoid and skin irritations at home

Sometimes the clearest proof of water tank contamination does not appear in the water glass, but on the body of family members living in the building.

If multiple tenants or family members continually suffer from unexplained stomach cramps, frequent bouts of typhoid, or persistent skin rashes and body itching shortly after bathing, your water supply is likely heavily infected.

Pathogens like Salmonella and harmful coliform bacteria thrive inside unwashed tanks, easily entering human bodies through small skin abrasions, accidental ingestion during showers, or contaminated eating plates. When sickness becomes a recurring monthly routine in an apartment block, the overhead tank is usually the hidden culprit.

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Step-by-step: how to safely clean and disinfect your water tank

Restoring safety to your domestic water supply requires a systematic cleaning process rather than a quick surface rinse.

First, turn off the main water pump power switch and isolate the tank outlet valve so dirty water does not flow down into house piping. Open the drain valve at the base of the tank or use a bucket to bail out the remaining water until only a few inches of water remain over the bottom mud layer.

Second, physically scrub the inner walls, floor, and corners of the tank using a clean, stiff-bristled brush to break off all slippery biofilm, algae, and stubborn mud crusts. Scoop out all the loosened dirty sludge completely using a small container and mop up remaining residues until the plastic surface is clean to the touch.

Third, disinfect the system thoroughly before refilling. Mix household liquid bleach (chlorine solution) with clean water at a standard ratio typically about one liter of regular household bleach for every thousand liters of tank capacity and brush it over the inner walls, allowing it to sit for at least two hours to kill remaining bacterial spores.

Finally, rinse the tank thoroughly with clean borehole water, flush the drain line completely, and refill the tank with fresh water. Ensure that the top lid is fitted with a tight lock or secure rubber seal to prevent sunlight, mosquitoes, dust, and wild birds from entering the tank ever again.