Buying Guide

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Frequently Asked
Questions
Q: What is the pressure rating of a given fitting?
A: Fittings are rated per Table 1 of ASME B16.22. The system rated
pressure shall be the lowest of the fitting, tube or joint.
Q: When copper fails in a system, what is the problem?
A: MOST COMMON:
1. Velocity – fluid is moving too fast. Recommendation:
2-3 fps (0.0508-0.0762 m/s) hot water 140°F, 5-8 fps (0.127-
0.2032 m/s) cold water.
2. Turbulence – burrs left on the cut tubing causes a tumbling
effect causing localized erosion and eventual failure.
3. Aggressive Waters – tend to cause pitting or green staining
of fixtures. Aggressive, hard well waters that cause pitting
typically are found to have total dissolved solids including
suflates and chlorides, a pH in the range of 7.2 to 7.8, a high
content of carbon dioxide gas and the pressence of dissolved
oxygen gas. Soft acidic waters that cause green staining
typically tend to be more corrosive. Low alkalinity, low
mineralization, pH levels lower than 8 should be avoided.
LESS COMMON:
1. Flux Corrosion – using too much flux when making
joints can potentially leave residue and cause isolated
corrosion. Flux should be used sparingly and system adequately
flushed.
2. Electrolysis – stray (D.C.) current; inadequate grounding for the
piping.
3. Sand or other solid particulates – erosion/corrosion problems
can occur. Lower velocities must be maintained
if solids are present in flow media.
4. Galvanic Corrosion – destruction of a material by
electrochemical interaction between the environment
and the material.
Q: Copper tubing wall thickness is designated “K,” “L” or “M.” What
are the copper fittings applicable to?
A: Copper fittings’ wall thickness is determined by standards (ASME
B16.22 and MSS SP-104). These standards address minimum wall
thickness (per size) for the full range of copper fittings and are not
intended to match tubing wall thicknesses.
Q: Can dissimilar metals (i.e., copper and iron) be joined together
without use of dielectric insulators to prevent corrosion?
A: In most situations dissimilar metals (copper/iron/steel) can be
joined successfully without using dielectric insulators. Factors to
consider:
1. The composition of the two metals.
2. The rate of liquid flow past the two metals.
3. Chemicals in the water which could enhance or destroy
protective films.
4. The relative areas of the two metals - unless the surface area
of the less noble (steel) material is less that 5% of the more
noble (copper) material, the need for a dielectric separator is
not needed. (Failures due to galvanic corrosion are very unusual
and only occur under very strict conditions.)
5. Local code requirements.
Q: What should the installer of copper unions know and do in order to
assure a proper leak-free installation?
A. The following should be done:
1. Make sure the ground-joint(mating area of unionís tail and
thread pieces) are free of nicks and scratches.
2. Spray the ground-joint area with a food grade silicone spray or
apply bees wax to enhance seating.
3. Make sure alignment of line does not put lateral stress on the
ground-joint seal.
4. Make sure that excess solder (droplets) do not reach the
ground-joint area.