It's not your imagination! Solder doesn't flow as well. Surface oxide is stubborn. Fittings don't heat up as easily.
Recent government regulations reduced the amount of lead in systems that carry water for human consumption. New lead-free fittings require some TLC to get a leak-free solder joint. Check out the printable Technique Sheet for details.
AGGRESSIVE MECHANICAL CLEANING
Requires an abrasive 120 grit or coarser.
As a result of tenacious surface oxide, aggressive mechanical cleaning is required, including the use of sandpaper or other abrasive cloth.
STANDARD FLUX APPLICATION
For best results, use a water soluble flux with chloride compounds.
Apply flux immediately after cleaning. To protect newly exposed metal and minimize reformation of oxide layer. Bernzomatic® brand Water Soluble Flux complies with the Reduction of Lead in Drinking Water Act — suitable for use with lead-free brass. Chlorides in the flux effectively aid in removal of oxides, providing superior adhesion of alloy to pipe.
THOROUGH HEATING & TORCH MOVEMENT
As a result of reduced thermal conductivity in lead-free brass, uniform heating throughout the fitting is critical. Adjust movement around the joint and heat gradually to achieve even temperature for soldering.
SOLDER CHOICE AND APPLICATION
Use a lead-free compliant solder, ensure NSF/ANSI Std. 61 compliance.
After joint is thoroughly heated, apply solder.
PROVIDE ADEQUATE TIME FOR COOLING
Because Lead-Free brass retains heat longer, the process requires more time for solder to solidify, cool and regain its strength.
For making capillary joints, Bernzomatic® recommends following the techniques found under ASTM standard B828.