- Effective catchment (with pitch)0m²
- Peak discharge0L/s
- Peak discharge0L/min
- Recommended pipe50mm downpipe
// Estimate only — verify before quoting
Drainage: Rainwater Discharge & Pipe Size Calculator
Sizes downpipes / gulleys for roof run-off per BS EN 12056-3. Tells you the litres-per-second and recommended pipe diameter.
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Browse the full shop →Frequently asked questions
How do I use the drainage: rainwater discharge & pipe size calculator?
Enter your measurements and options into the Drainage: Rainwater Discharge & Pipe Size above and the result updates instantly. Sizes downpipes / gulleys for roof run-off per BS EN 12056-3. Tells you the litres-per-second and recommended pipe diameter.
Is the drainage: rainwater discharge & pipe size calculator free to use?
Yes — every TradesMate calculator is free to use with no sign-up. Save quotes and use the full estimator with a free trial.
Are the results accurate enough to quote from?
The figures are reliable estimates based on standard UK trade practice. Always allow for wastage and verify against current material prices before quoting a customer.
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