Method
Rectangular water-tank geometry for capacity or required-footprint mode.
It covers two cases: capacity from dimensions and plan size for a required volume. Equations that apply to only one of them are tagged.
Equations
V = L · W · hcapacity from dimensions
A = Vreqhplan size
W = √Arplan size
L = r · Wplan size
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| L | Length | m |
| W | Width | m |
| h | Effective water depth | m |
| Vreq | Required volume | m³ |
| h | Selected water depth | m |
| r | Length-to-width ratio | – |
| Intermediate values | ||
| A | Plan area of water | m² |
| Results | ||
| V | Capacity / required volume | m³ |
| V | Capacity | L |
| L | Length | m |
| W | Width | m |
| h | Effective water depth | m |
Assumptions and limits
- No fire reserve or domestic reserve rule is applied.
In practice
- h is the effective water depth, between the outlet and the overflow level. No reserve is included: add any fire-fighting or other reserve your authority requires to the required volume, and freeboard to the tank height.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Method: Capacity from dimensions.
Inputs
| L | Length | 2 m |
| W | Width | 3 m |
| h | Effective water depth | 1 m |
Results
| V | Capacity / required volume | 6 m³ |
| V | Capacity | 6,000 L |
| L | Length | 2 m |
| W | Width | 3 m |
| h | Effective water depth | 1 m |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.