How to get a Waterproof Underground Concrete Water Tank

In every building be it residential, office, institute, hospital and so on we need to construct an underground concrete tank as a water reservoir.

Many times it happens that within a short period of time you face the problem of a leaking underground concrete water tank.

The problem of leakage may arise in a newly constructed water tank or an old water tank.

As you know prevention is better than cure. Hence, you must ensure to make the underground water tank waterproof during construction itself so that there is least possibility of the tank to leak after construction and also after many years of usage.

Waterproofing not only makes the water tank leakage-free but also gives strength to the structure.

Here are a few points that you must take care of during the construction phase

• The RCC water tank must be designed by a competent engineer - Reinforcements and Grade of concrete.
• Concrete mixing at site should be as per quality standards and as per the design mix. Weigh batching, Volume batching with concrete mixer is helpful.
• Line, level & dimension of each member of the tank should be maintained as per design.
• Placement of concrete with proper vibration techniques to release entrapped air and voids.
• Prevention of concrete-slurry loss during pouring and vibration with the use of cotton or foam plugs.
• Curing of the concrete structure after 24 hours for at least 7 days & up to 28 days. This is very important.

In addition to the above points, certain chemicals which have been developed as waterproofing chemicals are used at different stages of construction depending on the product to either make the concrete watertight and durable or to give a waterproof film layer blanketing the water retaining surfaces.

The theory states that concrete is watertight and truly so. This can be proved in a laboratory environment.

But all Civil engineers who are working in the construction field know the challenges they face while working at the site. 

The concreting conditions are most of the time not ideal and engineers need to meet the timelines.

Waterproofing is one field where much research has happened and many good products have been launched by various companies. 

What these chemicals do is help make the concrete impervious to water.

What will happen if Waterproofing is not done?

You will not face much problem in the structure in the first one year if there has been even an average quality of construction i.e. the construction been left to non-qualified supervisors and workers alone.

After the first year problems become visible. The root cause of most common problems is found out to be leakages, seepages, bulging and cracking of the concrete, plasters, pealing off the paints and dampness in the walls, formation of salty deposits.

Note that these problems might not appear in the whole of the structure. These are only at very small areas. 

Even these small problem areas will take away the peace of your mind and make you unhappy about your hard-earned investments. 

These problems do not stay at that, they grow in size very fast and exponentially. 

Many Technologies have been introduced by different companies in addressing the leakage problems in underground water tanks faced by engineers and owners in the country over the years.

You may ask, Will waterproofing not add to the cost of construction? Yes, waterproofing is costly. But it is worth the money spent. 

Believe me, I have seen from experience that the expenditure is worth having and will save much more in the long run. More importantly, it will buy you peace of mind.

For basic principles of concreting read waterproof underground concrete water tank 

Apart from adopting good practices during construction, we need to take care of the following

• The construction joints must be leak-proof.
• Treat the construction joints or cold joints using special methods.
• After construction and before usage, test the concrete tank by filling it with water and monitoring the water level inside, to identify any leakages.
• Pressure grout with 1:1 (Water: Cement) grout with the addition of waterproofing chemicals with the help of a manual pump if leakages are found at some points.

Use of waterproofing chemicals in concrete during construction 

Waterproofing chemical comes in liquid or powder form in different pack sizes.

For example, Dr Fixit Pidiproof LW+ from Pidilite Industries Ltd comes as a liquid in pack sizes of – 200ml, 1Ltr, 5Ltr, 10 Ltr, 20Ltr, 50 Ltr.

• The chemical is to be mixed with the concrete.
• The dosage of chemical is 200ml for 1 Bag (50Kg) of cement.
• The total concrete (Volume in Cum) to be used in the water tank can be easily calculated. You can follow my article on How to calculate the quantity of concrete in any structure. And the mix design will give the Bags of Cement / Cum of concrete. Read through the article on How to find cement bags quantity from mix design.
• Total chemical required will be 200ml x Total No. of Cement Bags
• Cost of 1 Ltr is about INR 155/-

Apart from waterproofing property, the chemical has some other benefits like

• Improvement in workability of concrete.

• Surface Cracking of Concrete is prevented.

• It protects the concrete from corrosion.

The chemical is easily available in the market. You may locate a dealer here (https://www.drfixit.co.in/locate/find-dealer)

Similarly, there are other chemicals too by Companies like Fosroc, Sika etc. 

I will bring you with similar other options with the comparative advantages and disadvantages.

Please let know how you look at this solution to waterproofing of underground concrete water tank. 

Write about your experiences and how you came out with an innovative idea. Let know what problems you are facing. 

We may find a solution together that will be helpful for all.