Hydronic Pipe Sizing Calculator
Size copper and steel pipe for hot water heating from BTU load per ASHRAE Fundamentals Ch. 22 and Bell & Gossett methodology
Free hydronic pipe planning calculator for HVAC contractors, mechanical engineers, and plumbing designers. Enter the heating or cooling load in BTU/hr and the design temperature differential to screen required GPM, local straight-pipe friction, and velocity for Copper Type L, Copper Type M, and Black Steel Schedule 40. The app includes ASHRAE, ASTM, CDA, Dow, and Bell & Gossett source pointers, but the local pipe rows, C factors, glycol properties, and limits remain planning data that need current source, manufacturer, project, and qualified review.
Check expansion-tank assumptions for the same loop
Expansion Tank Sizing Calculator →Calculate glycol performance penalties
Glycol Freeze Protection Calculator →Check pipe pressure drop for existing piping
Pipe Pressure Drop Calculator →Check pump affinity-law prompts before curve review
Pump Affinity Laws Calculator →How It Works
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Enter the Heat Load
Enter the BTU/hr load from a current load calculation, equipment schedule, or measured project basis. For multi-zone screens, add zones individually to compare branch and header assumptions.
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Set Screening Parameters
Choose design ΔT, pipe material, fluid type, local straight-pipe friction limit, and velocity limit. Treat the defaults as editable planning limits, not a code table or manufacturer rule.
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Review Source Gaps
Use the pipe comparison table as a first-pass straight-pipe calculator. Final design still needs equivalent length, fittings, valves, equipment drops, pump curves, glycol viscosity, material compatibility, code/AHJ, and qualified review.
Built For
- HVAC contractors documenting preliminary copper-pipe assumptions for residential baseboard loops
- Mechanical engineers checking early commercial hydronic branch and header flow screens
- Plumbing designers comparing local straight-pipe rows before a full pressure-drop model
- Service technicians comparing existing pipe sizes against updated load assumptions during renovations
- Solar thermal installers flagging glycol-flow caveats before product and pump review
References
- ASHRAE Handbook Fundamentals source pointer for pipe and tube design context
- Xylem / Bell & Gossett System Syzer hydronic design manual source pointer
- ASTM B88 and Copper Development Association source pointers for copper tube context
- ASTM A53/A106 source pointers for steel pipe context
- Dow product-page source pointers for glycol heat-transfer fluids
Frequently Asked Questions
Learn More
Expansion Tank Sizing for Hydronic Systems: Planning Method
How to size diaphragm expansion tanks using the ASHRAE formula. Gauge vs absolute pressure, glycol correction factors, system volume estimation, and common sizing errors.
Glycol Freeze Protection: Concentration, Performance, and Source Gaps
Selecting the right glycol concentration for freeze protection without over-concentrating. Freeze vs burst point, viscosity penalties, heat transfer derating, and annual maintenance.
Hydronic Pipe Planning: From BTU Load to Pipe Diameter
Sizing hydronic piping from heat load using ASHRAE friction and velocity guidelines. The magic "500" constant, glycol flow adjustment, and when to increase design delta-T.
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