Sweat fitting
From Wikipedia, the free encyclopedia
Sweat fitting is a means of joining copper tubing, using solder as a filler metal. Sweat connections are rapid to create, and offer a high degree of reliability. Until the mid 20th century, solder contained lead. Due to its toxicity even in trace amounts, now all solder used for potable water is required to be lead free.
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[edit] Making a sweat connection
Sweat fittings are smooth, and slide onto the outside of a tubing section. The areas where the tubing and fitting will join are cleaned with an abrasive cloth to expose the bare metal. In the case of wire (soft) solder, they are treated with flux paste, a petroleum compound which cleans the metal and helps solder to adhere. The joint is then heated with a torch and solder is melted into the joint. The molten solder is forced into the joint by capillary action, causing the solder to actually flow against gravity and fill the joint. The joint is then allowed to cool, and is fully hardened within minutes.
Sweat connections are usually considered the most difficult of the three methods of connecting copper tubing, but sweating copper is a very simple process, provided some basic conditions are provided:
- The tubing and fittings must be cleaned to bare metal with no tarnish
- The tubing must be completely dry of water until the joint is cooled
- Any pressure which is formed by heating of the tubing must have an outlet
If these conditions are met, the joint is heated thoroughly, and solder is applied all the way around the joint, the connection should be solid and leak-free.
[edit] Types of solder
Two varieties of solder are used currently, hard solder and soft solder.
[edit] Soft solder
Comes on a wire spool and is easily bendable. Soft solder is used in combination with flux paste on joints which supply potable water. It is non-toxic.
[edit] Hard solder
Also called silver solder (sold under the brand Sil-Foss), hard solder comes in rigids rods and contains a phosphorus flux mixture in the rod. No flux paste is used with hard solder. Due to the toxicity of phosphorus, hard solder should not be used for potable water lines. It is a popular choice for refrigerant lines in HVAC/R systems.
