10.Water Retaining Structures

10.Water Retaining Structures

1) Introduction

Water-retaining structures include potable/non‑potable water tanks, sumps, reservoirs, podium‑integrated pools, and channels. They face sustained hydrostatic pressure, thermal movement near the surface, and frequent penetrations. Systems must be watertight, tile/finish‑compatible where relevant, and maintain bond under head.

2) Exposures and risks

  • Continuous hydrostatic head (typically 2–6 m, higher for reservoirs)
  • Chemical exposure depending on service (chlorination, mild sulfates/chlorides)
  • Thermal cycling at exposed faces and copings
  • Movement at corners, junctions, and penetrations
  • Negative pressure during emptying for tanks

3) Recommended technologies

Technology
When to use
Key acceptance cues
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2K Elastomeric Cementitious (internal lining)
Default internal lining for pools, tanks, sumps (tile‑compatible)
Total DFT ≥2.0 mm; 72‑hr fill test pass; corner reinforcement
Cementitious Membrane
HDPE Pre‑applied bonded sheet
Positive‑side tanking where accessible (rafts/walls before casting)
Seam bond sound; overlaps ≥70–80 mm; no lateral migration
HDPE Membrane Waterproofing
PVC Sheet (loose‑laid, welded)
Large basins/reservoirs where double‑weld testing and compartments help
Double‑weld pressure test pass; weld logs recorded
PVC Sheet Membrane Waterproofing
Polyurea (spray‑applied)
High‑duty tanks/channels needing rapid turnaround and abrasion resistance
DFT ≥2.0–3.0 mm; adhesion ≥1.5 MPa; chemical spot tests (if applicable)
Polyurea Membranes
Crystalline (supplementary)
Secondary densification or negative‑side adjunct where rework limited
Two‑coat coverage on SSD; damp‑cure 3 days
Crystalline Waterproofing (Integral Powder & Surface-Applied Slurry)

4) Method statement (consultant‑ready)

  1. Pre‑works and substrate
    • Cure concrete to project requirement; grind/clean; repair honeycombs.
    • Provide 20×20 mm coves at all internal corners.
  2. Detailing
    • Treat penetrations with primer + bandage system; embed geotextile at corners and around inlets/outlets.
    • For positive‑side tanking: ensure substrate readiness, seam QA (sheet systems), and protection layers.
  3. Membrane/lining application
    • Cementitious: 2 coats crosswise to achieve ≥2.0 mm DFT; reinforce corners.
    • Sheet systems (HDPE/PVC): overlaps to spec; seam QA (pressure or probe tests).
    • Polyurea: primer to key; spray to target DFT in passes; topcoat if exposed.
  4. Protection and finishes
    • Screed/tiles where specified; follow adhesive system class (e.g., C2). Grout with epoxy for durability.
  5. QA and acceptance
    • DFT logs; seam test logs (sheet systems); adhesion pulls where relevant.
    • 72‑hr fill test; rectify and re‑test until pass.

5) Add‑ons and decision notes

  • Prefer positive‑side waterproofing where accessible; use negative‑side only as supplementary.
  • Compartmentalization and re‑injectable hoses are valuable on large tanks.
  • For potable applications, confirm product approvals.

Video Masterclass

SpecX Masterclass: Water Retaining Structures Waterproofing — Coming Soon

Disclaimer

SpecX is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.