Public Health
Water Demand Calculator
Estimate domestic water demand from occupancy, dwelling numbers or user-defined consumption rates.
Use this calculator for early-stage domestic water demand checks where a detailed fixture schedule is not yet available. It can be used for simple occupancy-based demand estimates, dwelling-based assessments or custom daily consumption inputs.
Inputs
Peak hour flow is estimated by converting daily demand to an average hourly flow and applying the selected peak factor.
Result
Method
Daily water demand may be estimated from occupancy and assumed daily usage:
Peak hour demand is then estimated from:
Peak flow is shown in both L/h and L/s.
- Daily Demand = total daily water demand (L/day)
- Peak Factor = applied diversity / peak hour multiplier
- Peak Hour Demand = estimated peak hour water use (L/h)
- Peak Flow = estimated peak hour flow converted to L/s
- Calculated result = -
Reference
- This calculator provides an indicative daily and peak hour water demand estimate for early-stage public health design.
- Occupancy-based demand assumptions should be checked against the building type, client brief and project-specific usage patterns.
- Peak demand estimation may later need refinement using fixture loading methods, diversity assumptions or utility requirements.
- Relevant guidance may include BS EN 806, the Water Supply (Water Fittings) Regulations and project-specific water authority criteria.