Greywater & Rainwater System Sizing Calculator
Use our free sizing calculator to estimate the water recycling potential for your commercial building. Designed specifically for M&E consultants, architects, and developers, this tool provides rapid volume estimates for greywater
yield, rainwater catchment, and attenuation requirements.
System Size & Savings Calculator
1. Building Details
2. Surfaces (Catchment)
Used for Rainwater & Stormwater
3. Location & Climate
4. Storm Water Maximum Outflow Rate
Allowable outflow to main sewer
5. Financials
Combined Supply + Wastewater
Rates effective 1 April 2025.
Advanced Parameters
Adjusts daily averages for intermittent use (e.g. offices).
Results
Total Non Potable Demand
Average Daily:
0.39 m³
Annual:
142.35 m³
Details: WC 0.14 m³ | Irrigation 0.00 m³ | Add. 0.00 m³
🚿 Greywater System
Avg. Daily Yield:
0.28 m³
Recommended Tank Volume
0.30 m³
Recommended MBR Filters (15m²)
1 Module
🌧️ Rainwater Harvesting
Annual Yield:
50.40 m³
Recommended Tank
2.50 m³
⚡ Stormwater Attenuation
Basis:
1:100yr Storm (+40% CC)
Required Attenuation Tank
3.50 m³
Based on Critical Storm duration
💰 Potential Savings
Annual Mains Water Saved:
102.20 m³
First Year Value:
£306
Estimated 24-Hour Non Potable Profile
Visual representation of greywater supply vs combined non-potable demand based on typical daily usage patterns.
10-Year Estimated Savings Forecast
Projected financial returns assuming a standard 4% annual increase in water utility costs.
📩 Request a Detailed Quote
Send your system calculations directly to our engineering team for a tailored proposal.
