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Lead-Free Solders for Copper, Brass and Stainless Steel Pipes and Tubing


KappZapp™ Silver Solders with the Highest Strength and Thermal Cycle Tolerance


KappZapp3.5™ and KappZapp4™ are the most common alloys used in soldering Copper to Copper, Brass and Stainless Steel tubes and pipes. Whether in solid wire, rosin, or acid cored, strength, vibration resistance, and thermal cycle resilience all go up with an increase in the Silver (Ag) content. The price also increases with the Silver Content. So the challenge is to choose the solder that meets your needs without buying more Silver than you need. Where strength and vibration resistance are not the primary criteria for your project, KappFree™ Tin-Copper-Silver solder is a more cost-effective Silver solder for most plumbing applications.


KappZapp3.5™ is the most convenient formulation, as it melts at the low eutectic temperature of 430°F / 221°C. For many hand soldering applications, KappZapp4™ is utilized for its wider slushy range of 430 - 475°F / 221 - 246°C. This allows the operator to fill large joints and manipulate parts during cooling, as well as prevents solder running off vertical joint surfaces.




96.5Sn - 3.5Ag


96Sn - 4Ag


93Sn - 7Ag



Solidus(°F) /(°C)

430°F / 221°C

430°F / 221°C

430°F / 221°C

440°F / 226°C

Liquidus(°F) /(°C)

430°F / 221°C

475°F / 246°C

570°F / 299°C

500°F / 260°C

Tensile Strength (copper)

14,000 psi

14,000 psi

15,500 psi

10,000 psi

Tensile Strength (stainless)

25,000 psi

28,000 psi

31,000 psi

18,000 psi

Shear Strength

11,600 psi

12,000 psi

14,000 psi

5,000 psi






Electrical Conductivity (%IACS)





Matching Kapp Soldering Flux

Kapp Comet™ Flux

Kapp Comet™ Flux

CopperBond™ Flux

Kapp Comet™ Flux


NSF International certifies that all KappZapp™ solders comply with NSF/ANSI Standard 372: Drinking Water System Components – Lead Content. Product also Certified to NSF/ANSI 61, Annex G and conforms with Lead content requirements for “Lead-free” plumbing as defined by California, Vermont, Maryland, and Louisiana state laws and the U.S. Safe Drinking Water Act in effect as of January 4, 2014. Weighted average lead content < 0.25%; Solder and flux lead content < 0.20%.

This alloy complies with the European RoHS and REACH directives. No lead, cadmium or mercury used in production.

KappFree™ High Strength Silver Solder for Most Plumbing Applications

KappFree solder was formulated specifically to provide the flow and bonding characteristics of higher Silver solders without buying more Silver than you need. It behaves similar to KappZapp™, and meets the stringent NSF Standard 372 requirements as Lead-Free and Cadmium-Free for potable water systems. KappFree™ meets the strength and thermal cycle requirements of most household plumbing needs. See the chart above for KappFree™ solder properties. KappFree™ solder is used with Kapp Comet™ Flux.


KappAnt™ and KappCu™ Lead-free Plumbing Solders

KappAnt Tin-Antimony solder is an NSF Standard 372 compliant Lead-free replacement for Tin-Lead solder in Copper tubing and cooling coils for refrigerators. Joints are of moderate strength where the higher strength and higher cost of KappFree™ or KappZapp™ Tin-Silver solders are not necessary. KappAnt™ solder is used with Kapp Comet™ Flux.


Specification: ASTM B32, Grade 95TA.


Technical Data


95% Tin / 5% Antimony



Melting Range:

452-464°F (234-240°C)

Tensile Strength:

5,900 psi

Shear Strength:

6,000 psi



Electrical Conductivity:

11.9 (%IACS)











KappCu™ Tin-Copper NSF-compliant solder replaces KappLead™ (Tin-Lead) solders in plumbing and Stainless Steel soldering applications. It is a low cost alternative to higher priced Silver solders and offers a wider workable range than KappAnt™ solders, allowing for joint build-up and adjustment during cooling.



  • Plumbing applications when joining Copper, Brass, or Stainless Steel
  • Situations where higher temperatures can be attained without harm to adjacent parts
  • Used extensively for large Stainless Steel products in the food service industry as well as potable water applications
  • Paired with Kapp CopperBond™ Flux

KappCu™ Properties


97% Tin / 3% Copper

Melting Range:

441-635°F (227-335°C)

Tensile Strength:

3,900 psi

Shear Strength:

4,000 psi




For any questions, please fill out the form below and a Kapp representative will contact you shortly.