What code dictates the allowable stresses for the steel staging structure?

IS 800 is referenced for the structural design and allowable stresses of the steel staging.

How is lateral loading calculated for overhead tanks?

Wind loads are derived from IS 875 (Part 3) and seismic forces from IS 1893 (Part 4), considering the structure as an elevated mass.

What is the standard procedure for testing the watertightness of the tank?

The tank is filled completely with water and observed for at least 24 hours to ensure there is no leakage or sweating at the joints.

What is the minimum thickness for the steel plates used in the tank body?

Typically 5 mm, but this increases depending on the depth of the water (hydrostatic pressure) and whether the plate is used for the bottom, sides, or roof.

IS 804

: 1989

Code of Practice for Design of Steel Structures for Overhead Water Tanks

CurrentSpecializedCode of PracticeBIMStructural Engineering · Tanks, Silos and Storage Structures

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This standard covers the design, fabrication, and erection requirements for steel overhead water tanks and their supporting structures (staging). It provides structural guidelines to ensure stability against lateral loads (wind and seismic) and dictates requirements for standard steel tank panels, joints, and watertightness.

Lays down requirements for the design of steel structures supporting overhead water tanks.

Quick Reference Values

standard panel size1.22 m x 1.22 m or 1.25 m x 1.25 m (Typical for pressed steel tanks)

minimum plate thickness5 mm (Increases with tank depth)

minimum freeboard150 mm

leakage test duration24 hours (tank filled completely with water)

flange width for panelsNot less than 45 mm

Practical Notes

When designing the staging (supporting structure), wind and seismic loads should be evaluated carefully, but as per IS codes, their maximum conditions are generally not assumed to act simultaneously.

Corrosion is a major failure mode for steel water tanks. Ensure robust protective coatings (epoxy paints, galvanizing) are specified and maintained.

For rectangular pressed steel tanks, standard pre-fabricated panels (usually 1.22m x 1.22m) are bolted together with appropriate jointing compounds to prevent leakage.