Thunderbird Roof Drain Estimator
Calculate the number of roof drains needed for your project based on your location's precipitation intensity and roof area.
Drain Requirements by Size
Calculation Summary
How It Works
Precipitation Intensity Data
Use verified NOAA Atlas 14 precipitation intensity data for accurate results. ZIP code estimates are for preliminary planning only.
Area Calculation
Each drain size can handle a specific roof area based on precipitation intensity using Thunderbird specifications.
Professional Design
Results are preliminary estimates only. Always consult a licensed engineer for final drainage system design.
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Shop Roof Drains →⚠️ CRITICAL PRECIPITATION INTENSITY DATA LIMITATIONS
ZIP CODE DATA NOT VERIFIED: The ZIP code precipitation intensity estimates in this calculator are broad regional approximations and have not been verified against actual NOAA Atlas 14 point precipitation intensity estimates. They may be significantly inaccurate for your specific location.
15-MINUTE vs 60-MINUTE INTENSITY: This calculator uses 100-year 15-minute precipitation intensity data. Some local building codes may require 60-minute intensities, which are typically 25-40% lower and will result in different drain requirements.
INTENSITY vs DEPTH: Always use precipitation intensity values (inches per hour), not precipitation depth (total inches). NOAA Atlas 14 provides both - ensure you select the intensity data.
MANDATORY VERIFICATION: For any actual construction project, you MUST obtain verified NOAA Atlas 14 precipitation intensity data for your exact coordinates at hdsc.nws.noaa.gov
PROFESSIONAL ENGINEERING REQUIRED: This tool provides preliminary estimates only. Licensed professional engineer consultation is mandatory for all final drainage system designs and code compliance verification.
Important Disclaimer
PRELIMINARY ESTIMATES ONLY: This calculator provides rough estimates based on Thunderbird Products specifications. Results are not suitable for final design or construction purposes without professional verification.
PRECIPITATION INTENSITY DATA ACCURACY: ZIP code precipitation intensity estimates are unverified regional approximations. Actual NOAA Atlas 14 intensity values may differ significantly. Always use verified site-specific precipitation intensity data for engineering purposes.
CODE COMPLIANCE: Building codes vary by jurisdiction and may require different precipitation intensity intervals, safety factors, or calculation methods. Always verify requirements with local authorities and follow applicable codes.
PROFESSIONAL CONSULTATION MANDATORY: Licensed professional engineer or architect consultation is required for all drainage system designs, code compliance verification, and construction documents.
NO LIABILITY: Thunderbird Products, Inc. assumes no responsibility for damages, failures, or inadequate performance resulting from use of this calculator. Users assume all responsibility for verification of precipitation intensity data accuracy and code compliance.