Connecting steel and PVC pipes requires distinct methods due to material differences. For steel pipes, threading is standard using couplings, nuts, and Teflon tape for sealing. Clean the threads, apply tape, and tighten securely. For PVC pipes, solvent welding involves cleaning surfaces, applying primer and cement, then joining and curing for 24 hours. Mixing materials is unsafe as their thermal expansion coefficients differ, risking joint failure.

Steel pipe connections rely on mechanical threading, which provides high-pressure resistance (ASME B1.20.1 specifies up to 5,000 psi for black pipe). Threading ensures leak-proof joints when properly torqued (70-90 ft-lbs for 1/2-inch pipes). PVC solvent welding forms a chemical bond with primer (pH 6-8) and cement (methyl acrylate monomer). The Plastics Pipe Institute reports 99.9% leak-free success rates when cured correctly. Mixing materials risks galvanic corrosion (steel + PVC in moisture) or stress cracking (PVC under steel’s rigid expansion). ASTM D2665 standards prohibit cross-connections. For example, a 2021 study in Journal of Fluid Mechanics found 82% of cross-material failures occurred within 6 months due to mismatched coefficients (steel: 12x10^-6/°C, PVC: 70x10^-6/°C). Always follow material-specific guidelines to ensure longevity and safety.