TryBuildCalcWater Tank Capacity Verification Checklist
🕒 Last updated: June 22, 2026
Essential Checklist+−
Complete these critical checks before approving the work or proceeding to the next construction stage.
✓20 Inspection Points
✓5 Verification Categories
✓Dimensions and Shape+-
- Tank dimensions were physically measured — not taken from the supplier's catalogue or a purchase invoice.
- Tank shape was correctly identified — rectangular, cylindrical, or L-shaped — before entering dimensions.
- For cylindrical tanks, the internal diameter was measured — not the external diameter. Wall thickness reduces the internal diameter by 20–60mm depending on material.
- For rectangular tanks, internal dimensions (length, width, depth) were measured after deducting wall thickness on all sides.
- Effective water depth was measured to the inlet pipe invert or overflow level — not to the top of the tank wall.
- Dimensions were entered in consistent units — all metres, all centimetres, or all millimetres.
- For underground or sump tanks, the usable depth was measured to the suction pipe invert — water below suction level is not accessible.
✓Demand Calculation+-
- Daily water demand was calculated from the number of occupants — IS 1172:1993 recommends 135 litres per person per day for residential use.
- Storage capacity covers the supply gap duration — number of days between municipal supply cycles was confirmed with the local authority.
- Overhead tank capacity is at least one day's demand; underground sump capacity is at least two to three days' demand.
✓Tank Material and Location+-
- Tank material is food-grade and BIS-certified — IS 12701 for plastic tanks, IS 2644 for ferrocement, IS 805 for steel.
- Overhead tank is structurally supported — the supporting structure was designed for the full tank weight when filled (1 litre = 1 kg).
- Tank location ensures adequate pressure head — minimum 2m height above the highest fitting for gravity-fed systems.
- Underground sump is located away from septic tank and soak pit — minimum 15m separation per IS 1172.
- Tank has a tight-fitting, vermin-proof lid — open tanks collect debris and mosquito breeding in still water.
✓Inlet, Outlet, and Overflow+-
- Inlet, outlet, and overflow pipe sizes were confirmed — undersized pipes restrict fill rate and create pressure loss.
- Overflow pipe discharges to a visible point — not directly into the drainage system where blockage would go unnoticed.
- A float valve or ball cock is fitted at the inlet to prevent overflow — confirmed as the correct size for the supply pipe.
✓Maintenance and Compliance+-
- Local municipal bye-law requirements for tank size, material, and location were confirmed before construction.
- For overhead tanks above 5,000 litres, structural engineer's certification for the supporting structure was obtained.
Full QC Checklist+−
Verify water demand, usable capacity, tank geometry, freeboard, and overflow.
✓31 Inspection Points
✓5 Verification Categories
✓Dimensions and Shape+-
- Tank dimensions were physically measured — not taken from the supplier's catalogue or a purchase invoice.
- Tank shape was correctly identified — rectangular, cylindrical, or L-shaped — before entering dimensions.
- For cylindrical tanks, the internal diameter was measured — not the external diameter. Wall thickness reduces the internal diameter by 20–60mm depending on material.
- For rectangular tanks, internal dimensions (length, width, depth) were measured after deducting wall thickness on all sides.
- Effective water depth was measured to the inlet pipe invert or overflow level — not to the top of the tank wall.
- Dimensions were entered in consistent units — all metres, all centimetres, or all millimetres.
- For underground or sump tanks, the usable depth was measured to the suction pipe invert — water below suction level is not accessible.
✓Demand Calculation+-
- Daily water demand was calculated from the number of occupants — IS 1172:1993 recommends 135 litres per person per day for residential use.
- Storage capacity covers the supply gap duration — number of days between municipal supply cycles was confirmed with the local authority.
- Overhead tank capacity is at least one day's demand; underground sump capacity is at least two to three days' demand.
- Water demand for non-domestic uses — garden irrigation, car washing, construction water — was estimated and added separately.
- Fire-fighting reserve was confirmed — IS 1172 and local bye-laws may require a dedicated fire reserve volume separate from domestic storage.
- Future occupancy increase was factored into the demand calculation for new constructions.
✓Tank Material and Location+-
- Tank material is food-grade and BIS-certified — IS 12701 for plastic tanks, IS 2644 for ferrocement, IS 805 for steel.
- Overhead tank is structurally supported — the supporting structure was designed for the full tank weight when filled (1 litre = 1 kg).
- Tank location ensures adequate pressure head — minimum 2m height above the highest fitting for gravity-fed systems.
- Underground sump is located away from septic tank and soak pit — minimum 15m separation per IS 1172.
- Tank has a tight-fitting, vermin-proof lid — open tanks collect debris and mosquito breeding in still water.
- A manhole or access opening of minimum 450mm diameter is provided for inspection and cleaning.
- Tank is painted or made of UV-resistant material if exposed to sunlight — direct UV degrades plain plastic tanks and promotes algae growth.
✓Inlet, Outlet, and Overflow+-
- Inlet, outlet, and overflow pipe sizes were confirmed — undersized pipes restrict fill rate and create pressure loss.
- Overflow pipe discharges to a visible point — not directly into the drainage system where blockage would go unnoticed.
- A float valve or ball cock is fitted at the inlet to prevent overflow — confirmed as the correct size for the supply pipe.
- The outlet pipe is 50–75mm above the tank floor to prevent sediment from entering the supply.
- A drain/washout valve is fitted at the lowest point of the tank for periodic cleaning.
- Inlet and outlet are on opposite sides of the tank to prevent short-circuiting of fresh and stale water.
✓Maintenance and Compliance+-
- Tank cleaning schedule — minimum once every six months — was confirmed with the building owner or maintenance team.
- Water quality testing was planned for new tanks before commissioning and annually thereafter.
- Local municipal bye-law requirements for tank size, material, and location were confirmed before construction.
- For overhead tanks above 5,000 litres, structural engineer's certification for the supporting structure was obtained.
- Tank capacity in litres was cross-checked against the result using: length (m) × width (m) × depth (m) × 1,000.
Inspection Notes+-
Use the latest approved drawings, specifications, and site measurements.
Complete all critical checks before proceeding to the next work stage.
Record deviations and confirm rectification where required.
Inspection Notes
Use the latest approved drawings, specifications, and site measurements.
Complete all critical checks before proceeding to the next work stage.
Record deviations and confirm rectification where required.