Basement, Water Tank & Sump Waterproofing

Basements and lift pits that stayed dry all year start weeping when the monsoon raises the water table. Water tanks lose level overnight. These are hydrostatic-pressure problems — they need crystalline or polymer-modified cementitious systems engineered for water-retaining and below-grade structures.

This collection includes crystalline waterproofing mortars, two-pack cementitious systems and flexible protective coatings suitable for basements, underground sumps, lift pits and water tanks (check each product page for potable-water approvals).

Read the complete basement waterproofing guide for positive vs negative side strategy, and estimate quantities with the calculator.

What Is the Best Waterproofing for Underground Water Tanks in India?

For underground water tanks storing potable (drinking) water, use crystalline cementitious systems like MC-Special DM applied to the water-facing surface (positive side). For non-potable tanks, two-component flexible cementitious coatings such as SikaTop 107 Seal Plus provide excellent adhesion and crack-bridging ability. Crystalline systems self-heal hairline cracks up to 0.4 mm, which is critical for tanks under continuous hydrostatic pressure from the surrounding water table. Always waterproof from the positive (water-contact) side for permanent results.

Should I Waterproof a Basement From Inside or Outside?

Waterproof from the outside (positive side) whenever the structure is accessible during construction. This places the membrane on the water-pressure side, which is more durable and prevents water from entering the concrete at all. For existing basements where external access is impossible, negative-side crystalline treatment (MC-Special DM) applied to the interior surface is the most effective retrofit option, as it generates crystals that block water within the concrete matrix itself.