AND CONDUITS FOR WATER- PIPE MATERIALS
The earliest known evidence of drain tile being used
for plumbing was found in Mesopotamia and is estimated to have been made around
3000 BC. The tiles were made from clay mixed with short lengths of straw. Both
brass and copper pipes have been found in Egypt believed to have been made
close to 2500 BC. The Romans made extensive use of lead pipe by joining sheets
of lead into piping to carry their water supply and waste. During the Dark Ages
following the fall of the Roman Empire, plumbing development virtually ceased
for centuries except for isolated cases of plumbing installed in palaces and
castles. In the 13th century, blacksmiths formed sheets of iron and lap welded
the seam to create iron pipe. Though it is unclear as to when galvanized iron
pipe was first used, a French chemist named Melouin is credited with developing
the process in 1742. The earliest known use for cast iron pipe is for the water
supply to a fountain in Langensalza,Germany, built around 1560. In 1819 the
first cast iron pipe constructed in the US, was manufactured in Weymouth, New
Jersey. Before that time, cast iron pipe and fittings had to be imported from
Europe. It was not until the 1960's that the hubless cast iron pipe was brought
to the U.S. from Europe by way of Canada. During the early 1900's, heavy-walled
copper joined with threaded fittings was in use, but limited to public
buildings because of its' high cost. However, during the 1930's light-gauge
Copper tube and fittings were developed which made copper economically feasible
and increased it's popularity. Polyvinyl Chloride(PVC) was produced
experimentally in the 19th century but did not become practical to manufacture
until 1926, when Waldo Semon of BF Goodrich Co. developed a method to
plasticize PVC, making it easier to process. PVC pipe began to be manufactured
in the 1940's and was in wide use during the DWV reconstruction of Germany and
Japan following WWII. In the 1950's, plastics manufacturers in Western Europe
and Japan began producing acrylonitrile butadiene styrene(ABS) pipe. The
methods for producing cross-linked polyethylene(PEX) was also developed in the
1950's. Plastic supply pipes have become increasingly common, with a variety of
materials and fittings employed, however plastic water pipes do not keep water
as clean as copper and brass piping does. Copper pipe plumbing is
bacteriostatic. This means that bacteria can't grow in the copper pipes.
Plumbing codes define which materials may be used, and all materials must be
proven by ASTM, UL, and/or NFPA testing.
Galvanized steel potable water supply and
distribution pipes are commonly found with nominal diameters from 3/8" to
2". It is rarely used today for new construction residential plumbing.
Steel pipe has National Pipe Thread (NPT) standard tapered male threads, which
connect with female tapered threads on elbows, tees, couplers, valves, and
other fittings. Galvanized steel (often known simply as "galv" or
"iron" in the plumbing trade) is relatively expensive, difficult to
work with due to weight and requirement of a pipe threader. It remains in
common use for repair of existing "galv" systems and to satisfy
building code non-combustibility requirements typically found in hotels,
apartment buildings and other commercial applications. It is also extremely
durable. Black lacquered steel pipe is the most widely used pipe material for
fire sprinklers and natural gas.
Most single family homes' systems typically won't
require supply piping larger than 3/4". In addition to expense, another
downside is it suffers from a tendency to obstruction due to internal rusting
and mineral deposits forming on the inside of the pipe over time after the
internal galvanizing zinc coating has degraded. In potable water distribution
service, galvanized steel pipe has a service life of about 30 to 50 years,
although it is not uncommon for it to be less in geographic areas with
corrosive water contaminants.
Generally, copper tubes are soldered directly into
copper or brass fittings, although compression, crimp, or flare fittings are
also used. Formerly, concerns with copper supply tubes included the lead used
in the solder at joints (50% tin and 50% lead). Some studies have shown
significant "leaching" of the lead into the potable water stream,
particularly after long periods of low usage, followed by peak demand periods.
In hard water applications, shortly after installation, the interior of the
pipes will be coated with the deposited minerals that had been dissolved in the
water, and therefore the vast majority of exposed lead is prevented from
entering the potable water. Building codes now require lead-free solder.
Building Codes throughout the U.S. require the use of virtually
"lead-free" (<.2% lead) solder or filler metals in plumbing
fittings and appliances as well.
Copper water tubes are
susceptible to: cold water pitting caused by contamination of the pipe interior
typically with soldering flux; erosion corrosion caused by high speed or
turbulent flow; and stray current corrosion, caused by poor electrical wiring
technique, such as improper grounding and bonding.
holes due to poor plumbing electrical grounding and/or bonding
Pin-hole leaks can occur anytime copper piping is
improperly grounded and/or bonded; nonmetal piping, such as Pex or PVC, does
not suffer from this problem. The phenomenon is known technically as stray
current corrosion or electrolytic pitting. Pin-holing due to poor
grounding or poor bonding occurs typically in homes where the original plumbing
has been modified; homeowners may find a new plastic water filtration device or
plastic repair union has interrupted the water pipe's electrical continuity to
ground when they start seeing pinhole water leaks after a recent install.
Damage occurs rapidly, usually being seen about six months after the ground
interruption. Correctly installed plumbing appliances will have a copper
bonding jumper cable connecting the interrupted pipe sections. Pinhole leaks
from stray current corrosion can result in thousands of dollars in plumbing
bills, and sometimes necessitating the replacement of the entire affected line.
The cause is an electrical problem, not a plumbing problem; once the plumbing
damage is repaired, an electrician should be consulted to evaluate the
grounding and bonding of the entire plumbing system.
difference between a ground and a bond is subtle. See Ground
(electricity), find the heading
power wiring installations for a complete description.
Stray current corrosion occurs because: 1) the
piping system is connected accidentally or intentionally to a DC voltage
source; 2) the piping does not have metal-to-metal electrical continuity; 3) if
the voltage source is AC, one or more naturally occurring minerals coating the
pipe interior act as a rectifier, converting AC current to DC . The DC voltage
forces the water within the piping to act as an electrical conductor (an
electrolyte). Electric current leaves the copper pipe, moves though the water
across the nonconductive section (the plastic filter housing in the example
above), and reenters the pipe on the opposite side. Pitting occurs at the
electrically negative side (the cathode), which may be upstream or downstream
with respect to the water flow direction. Pitting occurs because the electrical
voltage ionizes the pipe's interior copper metal, which reacts chemically with
dissolved minerals in the water creating copper salts; these copper salts are
soluble in water and wash away. Pits eventually grow and consolidate to form
pin holes. Where there is one, there are almost certainly more. A complete
discussion of stray current corrosion can be found in chapter 11, section
11.4.3, of Handbook of Corrosion Engineering, by Pierre Roberge.
Detecting and eliminating poor bonding is relatively
straightforward. Detection is accomplished by use of a simple voltmeter set to
DC with the leads placed in various places in the plumbing. Typically, a probe
on a hot pipe and a probe on a cold pipe will tell you if there is improper
grounding. Anything beyond a few millivolts is important, potentials of 200 mV
are common. A missing bond will show up best in the area of the gap, as
potential disperses as the water runs. Since the missing bond is usually seen
near the water source, as filtration and treatment equipment are added, pinhole
leaks can occur anywhere downstream. It is usually the cold water pipe, as this
is the one that gets the treatment devices.
Correcting the problem is a simple matter of either
purchasing a copper bonding jumper kit, composed of copper cable at least #6 AWG
in diameter and two bronze ground clamps for affixing it the plumbing. See NFPA
70, the U.S. National Electrical Code Handbook (NEC), section on bonding and
ground for details on selecting the correct bonding conductor wire size.
similar bonding jumper wire can also be seen crossing gas meters, but for a
Note, if homeowners
are experiencing shocks or sparks from plumbing fixtures or pipes, it is more
than a missing bond, it is likely a live electrical wire is bridging to the
plumbing and the plumbing system is not grounded. This is an electrical shock
hazard and potential fire danger; consult an electrician immediately!
Plastic pipe is in wide use for domestic water
supply and drainage, waste, and vent (DWV) pipe. For example, polyvinyl
chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene (PP),
polybutylene (PB), and polyethylene (PE) may be allowed by code for certain
uses. Some examples of plastics in water supply systems are:
- rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal
with municipal water pressure, introduced around 1970. PVC should be used for
cold water only, or venting. CPVC can be used for hot and cold potable water
supply. Connections are made with primers and solvent cements as required by
- The material is used primarily in housewares, food packaging, and clinical
equipment, but since the early 1970s has seen increasing use worldwide for both
domestic hot and cold water. PP pipes are heat fused, preventing the use of
glues, solvents, or mechanical fittings. PP pipe is often used in green
PBT - flexible (usually
gray or black) plastic pipe which is attached to barbed fittings and secured in
place with a copper crimp ring. The primary manufacturer of PBT tubing and
fittings was driven into bankruptcy by a class-action lawsuit over failures of
this system. However, PB and PBT tubing has returned to the market and codes,
typically first for 'exposed locations' such as risers.
- cross linked polyethylene system with mechanically joined fittings employing
barbs and crimped steel or copper fittings.
- plastic polyethylene cisterns, underground water tanks, above ground water
tanks, are made of linear polyethylene suitable as a potable water storage
tank, provided in white, black or green, approved by NSF and made of FDA
- known as PEX-Al-PEX, for its PEX/aluminum sandwich - aluminum pipe sandwiched
between layers of PEX and connected with brass compression fittings. In 2005, a
large number of their fittings were recalled.
Potable water supply systems require not only pipe,
but also many fittings and valves which add considerably to their functionality
as well as cost. The Piping and plumbing fittings and Valves articles discuss