Solder and Flux per Sweat-Joint Takeoff
Solder for a copper rough-in from the joint count.
Example
You enter
- Joints to sweat 200
- Solder wire per joint (in) 0.75
- Solder wire diameter (in) 0.125
- Solder density (lb/in³) 0.265
- Spool weight (lb) 1
You get
- W per in 0.003252
- Solder in the joints (order about 2x: CDA adds 100% for waste) 0.49 lb
- Spools 1
Checked against published worked examples from: Copper Development Association.
Details, formula, and sources
Scopeweight per inch = pi/4 x diameter^2 x density; solder = joints x wire per joint x weight per inch. 200 three-quarter-inch joints at about 0.75 in of 1/8 in solid wire each is 0.49 lb (one spool); a 2,000-joint job of 1 in pipe is 6.5 lb, seven spools. The wire per joint is a field rule (~the pipe diameter in inches); lead-free solder runs ~0.265 lb/in^3. That is the solder in the joints: the Copper Development Association's estimating weights add 100% for waste, so order about twice it, with about 2 oz of flux per lb of solder.
Formula or tablew_per_in = (PI/4) x wire_dia_in^2 x solder_density_lb_in3; solder_lb = joints x wire_in_per_joint x w_per_in; spools = ceil(solder_lb / spool_lb).
Source and editionSolder-weight identity by name (solid-wire cross-section x density x length); first-principles geometry.
Free accessThe wire weight is pure geometry (a length of solid wire of known diameter and density); the field wire-per-joint rule is public practice.
What governsEstimate. AHJ and licensed professional govern.
API field namesjoints, wire_in_per_joint, wire_dia_in, solder_density_lb_in3, spool_lb, w_per_in, solder_lb, spools
- Wire per joint ~the pipe diameter in inches of 1/8 in solid wire; varies with cup depth and techniquefield rule of thumb
- Solder density ~0.265 lb/in^3 for lead-free (tin-based) solder; 0.30 is a tin-lead figuresolder manufacturer