Water Tank Waterproofing in Chennai
Quick answerWater tank waterproofing seals the inside of a concrete or masonry tank with a coating that holds water under pressure and is safe for drinking water. Joints and cracks are repaired first, then the interior is coated and cured. In Chennai it typically costs ₹50 to ₹150 per sq ft of coated surface.
Why tanks leak in Chennai
Nearly every building in the city stores its water in an overhead tank, and that tank sits in the harshest spot on the property: the roof.
The outside of the tank bakes in direct sun while the inside stays cool and wet. That difference in temperature between the two faces of the same wall causes fine cracks over time. Water quality adds to it. Borewell and tanker water in many areas is high in dissolved salts, and treated supply carries chlorine. Both slowly attack plain cement plaster inside the tank.
Then there is the load. A 10,000 litre tank holds ten tonnes of water. That pressure sits on the wall-floor joint without a break, and a leak there falls straight onto the slab below, often above a bedroom.
Signs your tank needs attention
- Wet patches or algae on the outside walls of the tank
- White salt lines on the outer surface
- Dampness or dripping on the ceiling directly below
- Water level falling when no tap is in use
- The motor running more often than it used to
- Flaking plaster or exposed steel inside the tank
- Cracks around the inlet, outlet or overflow pipes
What is actually going wrong
The wall-floor joint is leaking.
This joint carries the highest water pressure and is usually a cold joint from construction. It is the first place to check.
Thermal cracks have formed.
Daily heating and cooling open vertical cracks, typically at the corners.
Pipe entries were never sealed.
Inlet, outlet, overflow and scour pipes pass through the wall. The mortar packed around them shrinks and leaves a ring-shaped gap.
Steel has started to rust.
Once moisture and salts reach the reinforcement, rust swells and pushes the cover concrete off. At that stage the tank needs structural repair before coating.
The plaster is porous.
Waterproof plaster is only as good as the workmanship on the day. Thin or badly cured patches seep.
The tank base is leaking onto the roof.
Where the tank sits directly on the terrace slab, a leaking base saturates the roof under it, and the complaint is often mistaken for a terrace leak.
Recommended systems
System | Best for | Typical life |
|---|---|---|
Crystalline cementitious coating | Concrete tanks, seals pores from within | Life of the concrete |
Food-grade epoxy coating | Smooth, easy-to-clean finish for drinking water | 8 to 10 years |
Polymer-modified cementitious coating, potable grade | Masonry and plastered tanks | 7 to 10 years |
Non-shrink grout and sealant | Pipe entries and wall-floor joints | Part of the system |
Injection grouting | Leaking cracks and cold joints | Permanent repair |
Exterior elastomeric coating | Outer walls and tank cover, cuts heat stress | 5 to 7 years |
Only coatings certified for contact with drinking water go inside a tank. We share the product data sheet before work begins.
How we do the work
- Inspection.We check the tank inside and out and the slab below.
- Empty and clean.The tank is drained, sludge removed and the surface washed down.
- Ventilate. Fresh air is provided before anyone works inside the tank.
- Repair. Loose plaster is removed. Cracks are opened and filled. Rusted steel is treated.
- Seal the joints.Pipe entries are repacked with non-shrink grout. A coving is formed along the wall-floor joint.
- Grout where needed.Leaking cold joints are injected.
- Coat.Two coats on floor and walls, the second at right angles to the first.
- Cure.The coating is cured as the product requires, usually five to seven days
- Rinse and refill.The tank is washed, disinfected, filled and checked for 48 hours.
Cost in Chennai
Work | Indicative rate |
|---|---|
Interior waterproof coating | ₹50 to ₹150 per sq ft |
Injection at leaking joints | ₹250 to ₹600 per injection point |
Structural repair of rusted sections | Quoted after inspection |
The rate depends on tank condition and the coating chosen. Small domestic tanks are often quoted as a lump sum.
Frequently asked questions
Is the coating safe for drinking water?
Yes. We use only coatings rated for potable water, and the tank is rinsed and disinfected before refilling.
How long will we be without the tank?
About a week, mostly curing time. Rushing the cure is the main reason tank coatings fail.
Can you fix it from outside without emptying the tank?
Outside patching rarely holds because water pressure pushes it off. The repair must be done on the inside face.
Do you treat plastic tanks?
No. Cracked plastic tanks are better replaced. Our work covers RCC and masonry tanks.
How often should a tank be re-coated?
Inspect it during the yearly cleaning. A good system lasts eight to ten years or longer.
Is there a warranty?
Yes, a written warranty is issued after the fill test.