A leaking water tank is more than a nuisance. It wastes stored water, stains and weakens the structure around it, and encourages algae and fungus to grow. But water tanks come with a condition no other waterproofing job has: whatever you coat the inside with has to be completely safe for drinking water.
This guide explains how to waterproof overhead and underground tanks properly, which potable-safe products to use, and the correct method from surface preparation to leak test, using products we stock from Dr. Fixit and Sika. For the full picture of protecting your building, see our complete waterproofing guide for Panchkula.
Why water tanks need special waterproofing
Tanks are built to hold water day and night, so any weakness shows up fast. Waterproofing a tank does three jobs at once:
- Stops leakage that wastes stored water and damages the surrounding structure.
- Prevents algae and fungus, which take hold where damp and seepage persist and can weaken the concrete over time.
- Protects the concrete from the constant water contact that slowly breaks down an untreated surface.
The catch is that the coating sits in direct contact with water you may drink, so it must be chosen with that in mind.
The key rule: use only potable-safe coatings
This is the one rule you cannot skip. The inside of a drinking-water tank must be coated only with a product certified safe for potable water. In India, the recognised approval for this is CFTRI certification, from the Central Food Technological Research Institute in Mysore.
Both of the main Dr. Fixit tank coatings, Pidifin 2K and Dampguard, are CFTRI certified as safe for potable water, so they do not affect the taste or safety of stored water. Never use an ordinary coating or a general-purpose waterproofing paint inside a drinking-water tank.
Products for water tank waterproofing
- Dr. Fixit Pidifin 2K: a two-component acrylic cementitious coating, CFTRI certified for potable water. Flexible and strongly bonding, it works on both the positive and negative sides, which makes it well suited to tanks. It is the common choice for the internal walls of domestic water tanks.
- Dr. Fixit Dampguard: a two-component, food-grade certified epoxy coating for RCC water tanks. It resists water, fungus and microbial growth, and can be applied over damp surfaces.
- Dr. Fixit Pidicrete URP: an SBR latex bonding agent used to grout construction joints with polymer-modified mortar before coating.
- Dr. Fixit Pidiproof LW+: the integral admixture for the tank’s plaster, adding water resistance from within the mortar.
- Sika SikaTop 107 Seal Plus: a two-component cementitious waterproofing coating suitable for water tanks, if you prefer the Sika system.
We stock these Dr. Fixit and Sika construction chemicals and can advise on the right one and the quantity for your tank size.
How to waterproof a water tank step by step
Whether the tank is overhead or underground, the method follows the same logic. Preparation and a proper leak test are what make it last.
1. Empty and clean the tank
Drain the tank fully and clean the inside surfaces, removing dirt, oil, algae and any loose material. The surface must be sound before anything goes on.
2. Cure, repair and grout the joints
For a new tank, let the concrete cure fully first. Repair all cracks, undulations and voids. Grout the construction joints with a polymer-modified mortar made using Dr. Fixit Pidicrete URP, since joints are a common leak path.
3. Bring the surface to the right condition
Prepare the surface to a saturated surface dry condition, meaning damp but with no standing water, before applying a cementitious coating. Follow the datasheet for the specific product.
4. Apply the potable-safe coating
Apply the coating in two coats, working the first well into the surface. Where a protective plaster will follow on the internal walls, sprinkle coarse sand over the wet second coat so the plaster keys to it.
5. Cure the coating
Allow the coating to cure fully. Curing is what gives the coating its strength and water resistance, so do not rush it.
6. Do a pond test
After proper curing, do a pond test. For a cementitious system like Pidifin 2K, this is carried out only after around seven days of curing: fill the tank, leave it, and check for any drop in level or signs of leakage on the outside. Only a tank that passes is ready.
7. Flush before storing drinking water
Before putting the tank into use for drinking water, flush and rinse it thoroughly with clean water several times, so it is completely clean for storage.
Overhead tanks and underground tanks are not the same
The products are similar, but the challenges differ.
- Overhead tanks sit exposed on the roof, so the outside also faces sun and rain. The inside is coated for potability and leak resistance, while the outside can be treated like any exposed surface.
- Underground and sump tanks face water pressure from the surrounding ground as well as from inside. This is where a coating that resists both positive and negative pressure, such as Pidifin 2K, earns its place, since ground water can try to push in from outside.
Tell us which type you have and we will match the products to it.
Common mistakes to avoid
- Using a non-potable coating inside a drinking-water tank. Only use CFTRI-certified, potable-safe products.
- Ignoring the construction joints. Joints and cracks leak first, so grout them properly before coating.
- Coating a green, uncured tank. New concrete must cure before waterproofing.
- Skipping the pond test. Test for water tightness before the tank goes into service.
- Not flushing before use. Rinse the tank thoroughly before storing drinking water.
Water tank waterproofing materials in Panchkula
Building a new tank or fixing a leaking one? Tell us the tank type and size and we will recommend the right potable-safe Dr. Fixit or Sika products and quantities. Khandelwal Trading Co. serves Panchkula, Chandigarh, Mohali and the wider Tricity.
- Visit: Shop No. 4, Street No. 2, Maheshpur, Sector 21, Budanpur, Panchkula, Haryana 134117
- Call: 94175 65977
- WhatsApp: message us here
- Trade enquiry: get a quote
Frequently asked questions
Is water tank waterproofing safe for drinking water?
It is, as long as you use a potable-safe product. Coatings like Dr. Fixit Pidifin 2K and Dampguard are CFTRI certified as safe for potable water and do not affect taste or safety. Never use an ordinary waterproofing coating inside a drinking-water tank.
Which is the best product for water tank waterproofing?
Dr. Fixit Pidifin 2K is a common choice because it is potable-safe and works against both positive and negative water pressure. Dampguard, a food-grade epoxy, is another. Grout the construction joints first with Pidicrete URP for a fully sealed tank.
Can I waterproof a tank from the inside?
Yes, coating the inside with a potable-safe product is the usual approach. Underground and sump tanks especially benefit from a coating that resists negative pressure, since ground water can push in from outside.
How do I test whether my tank is leak-free?
Do a pond test after the coating has cured. For a cementitious system this is usually after around seven days: fill the tank, leave it, and watch for any drop in level or damp patches outside.
Do I need to do anything before using the tank after coating?
Yes. Flush and rinse the tank thoroughly with clean water several times before storing drinking water, so the surface is completely clean.
