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Waterproofing Water Tanks




  • All surfaces to be waterproofed must be firm, clean, dry, sound and smooth. All grease, oil, wax, curing compounds, loose material, paint and any other contaminants must be removed, surfaces must be pointed flush and surface defects repaired.

  • External corners to be waterproofed must be bevelled to ensure a smooth transition of membrane from vertical to horizontal surfaces.


  • If the area to be waterproofed is subject to continuous water seepage, seal off the flow using Mapei Lamposilex, then continue as described below. Lamposilex is an Ultra-fast setting and drying hydraulic binder for plugging water leaks.

  • Apply a coat of Mapefil GP to all masonry surfaces. Mapefill GP is a general purpose non-shrink grout recommended for grouting voids in structural elements.

  • Install a 40mm x 40 mm cove to all vertical and horizontal internal corners using Mapegrout T40. Mapegrout T40 is a medium strength (40 MPA), fibre reinforced, thixotropic grout for repairing concrete. Mapegrout T40 can also be used to repair surface defects in masonry building elements.

  • Install a gun-able water stop around all penetrations. The water stop must be packed in between at least a 50 mm cover of Mapegrout T40. Gun-able water stop products are caulk grade (gun-able), single component swelling pastes used to stop water infiltration through concrete construction joints

  • Prime PVC and metal pipes using WPA 160. WPA 160 is a specialised solvent free primer designed for enhancing the adhesion of subsequent membranes, adhesives, toppings and decorative finishes over porous or non-porous substrates.

  • Install a reinforcement layer over all coves using Mapelastic Smart. Incorporate Mapei Fibreglass Mesh into reinforcement coat. Mapelastic Smart is two-component, flexible cementitious mortar for waterproofing concrete surfaces subject to negative and positive hydraulic pressure.

  • Fibreglass Mesh Alkali-resistant fibreglass mesh for reinforcing interior and exterior levelling compounds.

  • Install two coats of Mapelastic Smart ensuring that a minimum dry film thickness of at least 2mm is achieved.

IMPOTRANT: Allow membrane to cure for 10 days with fan forced ventilation.