How to Cast Reinforced Concrete Water Tank Walls (Step-by-Step)

Building a watertight RC water tank isn’t just “another pour”—it’s a tightly sequenced operation where setting-out, waterstops, formwork, vibration, and QA all have to be right the first time. Below is a site-ready guide distilled from an approved Method Statement for Casting the Water Tank Walls, adapted to our London workflows.

Scope & prerequisites

• Purpose: deliver crack-controlled, watertight walls with accurate geometry and coordinated MEP sleeves. 
• What you need on site: approved reinforcement, formwork system (e.g., Doka Top50), waterstops, shutter release agent, binding wire; concrete pump with boom; survey kit (total station, level); competent crew (PM, site & QC engineers, steel fixers, carpenters, MEP coordinators, safety officer). 

Sequence of works

1) Safety & setting-out

• Toolbox talk; barricade pour area; verify access/egress and lighting.
• Survey the wall lines and levels; confirm offsets/tolerances before any steel or shutters are fixed. 

2) Reinforcement & waterstops

• Clean the construction joint (remove laitance), repair honeycombs, and confirm cover blocks/spacers.
• Fix steel per AFC drawings; maintain specified lap/cover and keep starter bars free of mortar.
• Install the waterstop centrally in the wall thickness—it must resist hydrostatic head during and after casting. Raise an Inspection Request (IR) 24 hrs before pour for the supervising engineer. 

3) MEP sleeves & embeds

• Pre-fix all sleeves, puddle flanges, and conduits to shop-drawing locations and heights; no ad-hoc drilling later. Coordinate checks with the MEP engineer before shutters close. 

4) Formwork—fixing & closure

• Erect the Doka Top50 (or equivalent) to the approved layout; apply release agent uniformly; plumb, level, and brace to resist pour pressure.
• Close shutters with the waterstop continuous and rebar undisturbed; remove loose debris/dust from the kicker. 

5) Pre-pour inspections

• IR sequence: A) Rebar & 1st-stage shutters, B) Pre-pour (2nd-stage shutters & concrete placing plan), C) Separate MEP IRs attached to B after clearance. Record dimensional checks and sign-offs. 

6) Concrete delivery, placing & compaction

• On arrival, test temperature and slump to spec; stage the pour to keep a live front.
• Place concrete immediately after checks; use internal vibrators (25–50 mm) in lifts not exceeding ~300 mm, working around rebar and embeds to avoid voids.
• Limit free-fall to ≤1.5 m; use tremie/chute/elephant trunk if needed. Do not “break cohesion” with the crane; use wedges/pry-bars as specified when lifting shutters. 

7) Finishing, cleaning & early-age care

• Clean residual laitance from forms; debond cone inserts; patch as approved. Provide safe platforms for access and keep the wall protected from impact and rapid drying. 

8) Striking formwork (de-shuttering)

• Observe stipulated striking times—as a rule, wait at least 24 hrs before attempting strike, then remove connectors and ties in sequence while maintaining stability. Follow the method statement’s step-by-step stripping order. 

Quality control & testing

• Tolerances: check section dimensions, verticality, position, and alignment against the MS schedule (e.g., verticality ±15 mm, position ±10 mm—confirm project-specific values).
• Testing: take concrete samples/cubes for compressive strength to EN 12390 series and maintain full IR and QC records (checklists, scan & file). 

Pro tips from our London crews

• Use hydrophilic strips at kicker/stop ends to complement central waterstops on critical joints.
• Pre-plan cold-joint heights with pour-stop angles and needle-vibration access.
• Specify cover blocks from non-absorbent polymer concrete in wet zones to avoid soft spots.
• Lock the IR, cube schedule, and pour log into your site QA pack and reference it in the ITP.

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