Water Tank Cleaning: How often should you do it?


Water Tank Cleaning: How often should you do it?

“It seemed like a mysterious illness, one by one almost all the residents of tower A started getting sick with stomach upset and diarrhea.”

One of our employees was narrating this suspense story to us on a Monday morning. Over the weekend, a lot of the residents of a particular tower in their housing society had fallen prey to some sort of a stomach infection. While the residents of other towers were perfectly ok.  After much thinking, detective work, and questioning they found the culprit – a dead rat in Tower A’s overhead water tank!

As is the norm in most housing societies, the security guards were instructed to check the tank levels twice a day and turn the pump on accordingly. On that particular night, the security guard left the tank lid open for the overhead tank of Tower A. A rat fell inside and created a health epidemic over the next 2-3 days.

This incident demonstrates how important it is to maintain the cleanliness and security of our water tanks.

Read- Water Management in Housing Societies Part 1

Why should we keep our water tanks clean?

Just as we take care of our water filters – getting them serviced regularly, making sure the lids of the water container and bottles are closed. We must treat our water tanks as an extension of our water system just like our water bottles, water filters, and buckets. 

Waterborne diseases cause up to 3.4 million deaths each year, making it one of the largest causes of disease and death around the world. Unhygienic water conditions are a major problem in rural India. Contaminated water can transmit diseases such as diarrhea, cholera, dysentery, typhoid, salmonella, etc.

diseases caused by drinking polluted water

The Water Tank cleaning process

While all of us talk about tank cleaning and water quality, very few people have actually opened the lid of a water tank and peered inside.  To get more insight about the tank cleaning process, we spoke to Mr. Ajit Bapat, owner of a tank cleaning service in Mumbai. 

Mr. Bapat has about 20 years of experience in the tank cleaning business and has offered his services to thousands of buildings across Mumbai, including the Sahar International Airport in Andheri and the World Trade Center Building in Colaba.

He has also shared some tips related to the things the society residents or management committee members should watch out for when getting the tanks cleaned.  We have shared them in the next section.

Read- Water Management in Housing Societies Part-2

Step by Step Water Tank Cleaning Process

  • Creating a schedule for cleaning underground and overhead tanks.
  • Intimating the Managing Committee/ Society Manager. Clearly instructing them in advance to keep the tanks as empty as possible for the cleaning process so as to save water.
  • Dewatering the tanks
    • Dewatering is the process of removing water from an area.
    • It is difficult and complicated to dewater the bottom 1 inch of water in any tank. The bigger the tank, the harder it is.
    • Typically, a vacuum is used to dewater the bottoms of tanks. However, if the tank is made of concrete, the bottom will be rough and grainy; hence a vacuum may not work and a dewatering pump should be used instead.
    • Sometimes, if nothing works, the last resort will be to use a broom, mop and dustpan to remove the water.


  • Spray the sidewalls
    • The side walls are sprayed with a mild solution of Hydrogen Peroxide or Potassium Permanganate
    • The spray pump can be operated in a jet or spray mode. It also comes with a regulator so that its speed and power can be regulated
    • The pump has to be operated carefully by an experienced person.
    • The side walls need to be sprayed powerfully so as to dislodge all the sludge and deposits along the wall. At the same time, it should not be so strong that the water tank walls are damaged.
    • The sprayer needs to consider whether the tank is made of RCC, steel, cement or other materials and use chemicals and spraying pressure accordingly.
    • The bottom is sprayed and scrubbed much more rigorously than the side walls as sticky deposits settle down at the bottom.
    • After spraying and washing with the cleaning solution, the sidewalls and bottom are sprayed and cleaned with regular water
    • Overall, the sidewalls and the bottom are sprayed 4-5 times in total


What to keep in mind when getting your tank cleaned?

Most society residents have full-time day jobs and look into society maintenance matters only when time permits. As a result, tank cleaning is simply outsourced to an external agency or the watchman and at the end of the day, the residents just assume that the tank has been cleaned.

Based on his years of experience, Mr. Bapat has advised the society residents to take care of the following things when getting their water tanks cleaned –

  • Inform residents in advance so they can make arrangements.
  • Plan beforehand so that minimal water is wasted.
    • E.g., All the water from the UG tanks can be pumped to the OH tanks to get the UG tanks cleaned, and vice versa.
    • Or you can choose to wash the parking garages and other areas of the society on the same day so that the water in the tanks does not get wasted.
  • Supervising the tank cleaning activity
    • Tank cleaning personnel are semi-skilled, so make sure either you or the manager supervises the cleaning activity.
    • Ask them about the chemicals they will be using for cleaning.
    • Do ask the cleaning staff if they noticed any leakages, cracks in the sidewalls of the tanks just for your information.
  • Create a proper plan for emptying the tanks before cleaning and filling them.
  • Sometimes it takes a few hours for the overhead tanks to fill up; so, create an appropriate schedule to minimize water wastage and inconvenience.
  • Determine the appropriate frequency for getting tank cleaning done for your complex. You can take the following into consideration.
    • WHO recommends that tanks be cleaned once every 3 months.
    • Typically, in the Indian environment, it is recommended to get tanks cleaned every 6 months.
    • Is your tank located in a sunny area or a shaded area (sun rays are disinfecting)?
    • Do your tanks typically store hard water or soft water?
    • Are the tanks being supplied by underground pipes or overhead ones (UG pipes can carry the risk of contamination if the construction is very old)?
    • What is the turnaround time for the water in your tank? Or for how long does the water stay stagnant in your tank?


So, here is a recap of all that we’ve covered so far

  • Water tanks are an invisible but integral part of the water system.
  • Regular tank cleaning is not something to be ticked off the checklist like conducting a fire drill. It is a fundamental responsibility that needs to be taken care of in the right way. If not done properly, it could be directly hazardous to your health. 

The above steps can be used to provide a proper guideline for effective cleaning of water tanks in your society.

In the next blog, we will brief ourselves on the right equipment needed for water management, and decide the right system for our society.

Water Tank Cleaning: How often should you do it?

One thought on “Water Tank Cleaning: How often should you do it?

  1. Very informative post regarding sump and tank cleaning. Water tank and sump if not cleaned can create health issues and many people totally ignore the cleaning. I have worked in a company which provided sump and water tank cleaning services in Chennai and almost all the water tank and sump tank were with fungus and dirty. Posts like these emphasizes on the importance of keeping them clean.

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