solder joints and propane

[Bud Kennedy]

Someone on here said to NEVER use solder type joints on copper propane fittings. I have never heard this and am wondering why this may be true given that I have recently installed a refrigerator using a solder in "T" fitting.

[Mark Shaffer]

Bud, typical solder for water lines are 60% tin and 40% lead. The solder joint can crack or break if the line is disturbed. Now, if you used silver solder, that makes a stronger bond and will work better than the standard water line or plumbing solder. I have used silver solder on refrigeration lines and gas lines with no problems, but my fitting of choice is a compression type fitting where you flare the copper gas line.

[Curtis F.]

^ +++.

[Darwin Maring]

I have never heard that however I do agree with Mark that if you do, use silver solder.

Mark, It is my understanding that plumbing solder should be lead free. Look at it the next time you're in Home Depot.

[Mark Shaffer]

Tin/Lead solders, also called soft solders, are commercially available with tin concentrations between 5% and 70% by weight. The greater the tin concentration, the greater the solder’s tensile and shear strengths. At the retail level, the two most common alloys are 60/40 Tin/lead (Sn/Pb) which melts at 370 °F or 188 °C and 63/37 Sn/Pb used principally in electrical/electronic work. The 63/37 ratio is notable in that it is a eutectic mixture, which means:

1. It has the lowest melting point (183 °C or 361.4 °F) of all the tin/lead alloys; and
2. The melting point is truly a point — not a range.

In plumbing, a higher proportion of lead was used, commonly 50/50. This had the advantage of making the alloy solidify more slowly, so that it could be wiped over the joint to ensure watertightness, the pipes being physically fitted together before soldering. Although lead water pipes were displaced by copper when the significance of lead poisoning began to be fully appreciated, lead solder was still used until the 1980s because it was thought that the amount of lead that could leach into water from the solder was negligible from a properly soldered joint. The electrochemical couple of copper and lead promotes corrosion of the lead and tin, however tin is protected by insoluble oxide. Since even small amounts of lead have been found detrimental to health,[3] lead in plumbing solder was replaced by silver (food grade applications) or antimony, with copper often added, and the proportion of tin was increased.