COPPER PIPES PROS AND CONS
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GAINESVILLE ALACHUA COUNTY 352-335-8555
Serving all of Florida and Georgia at 904-346-1266
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Copper piping provides a relatively reliable material under most conditions due to the formation of a protective layer of cuprous oxide that protects it in most environments. However, a recent series of failures of underground copper water supply pipes have been reported near Miami, Florida. All of these failures involve type L copper pipe located under concrete slab-on-grade foundations in a single sub-division. All of the copper plumbing under the slab is encased in a continuous plastic sleeve as required by the state building code. The rationale for the sleeve is to protect the sub-slab copper pipe from aggressive soils, groundwater, and concrete leachate.
One builder last reported failures in 20 homes, some of which incurred multiple failures. The plumber who installed the copper supply pipes indicated that a second builder is facing similar problems, although these could not be confirmed. This report contains results of a preliminary investigation of failed plumbing materials retrieved from two homes.
INVESTIGATIVE REPORT OF COPPER
PLUMBING FAILURES UNDER
CONCRETE SLABS
Prepared for
National Association of Home Builders
1201 15th Street, N.W.
Washington, D.C. 20005-2800
by
NAHB Research Center
400 Prince George’s Boulevard
Upper Marlboro, Maryland 20772
August 1992
TABLE OF CONTENTS
PAGE
INTRODUCTION 1
BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
FLORIDA INSTALLATIONS ………………………………… 3
METALLURGICAL INVESTIGATION ………………………….. 3
RESULTS 4
RECOMMENDATIONS ……………………………………. 4
………………………………………..
……………………………………………..
APPENDIX A
Failure Analysis
APPENDIX B
Soil Tests
INTRODUCTION
Copper piping provides a relatively reliable material under most conditions due to the formation
of a protective layer of cuprous oxide that protects it in most environments. However, a recent
series of failures of underground copper water supply pipes have been reported near Miami,
Florida. All of these failures involve type L copper pipe located under concrete slab-on-grade
foundations in a single sub-division. All of the copper plumbing under the slab is encased in a
continuous plastic sleeve as required by the state building code. The rationale for the sleeve is
to protect the sub-slab copper pipe from aggressive soils, groundwater, and concrete leachate.
One builder last reported failures in 20 homes, some of which incurred multiple failures. The
plumber who installed the copper supply pipes indicated that a second builder is facing similar
problems, although these could not be confirmed. This report contains results of a preliminary
investigation of failed plumbing materials retrieved from two homes.
BACKGROUND
Reviews conducted by Waters’ and by Myers and Cohen2 suggest the following mechanisms
can cause copper corrosion by acting alone or in combination.
Abnormally aggressive soils. This is typically due to the presence of soils with elevated
sulfate or chloride levels and a capacity to retain moisture.
Electrochemical concentration cells created by differences in soil composition. For
example, backfill soils with a high oxygen content relative to the supporting soil can
cause corrosion of the under side of a pipe.
‘Waters, D.M., “Internal and External Copper Corrosion in Domestic Water Services,” Proceedings of AWWA
Annual Conference, Anaheim, CA, May 1977.
2Myers, J.R., and Cohen, A., “Conditions Contributing to Underground Copper Corrosion,” Journal AWA,
August 1984.
1
Stray electrical currents. One utility company’s experience with stray AC currents
resulting from bonding of the electrical system to the plumbing system suggest that this
practice should be stopped in favor of other grounding methods3.
Thermal galvanic effects. This frequently results from contact of hot and cold metal pipes
causing corrosion of the hot water pipe.
Galvanic action due to contact of dissimilar metals.
Corrosion fatigue caused by thermal expansion and contraction. This rare type of failure
usually occurs with flared joints or where copper passes through a concrete slab.
A review of technical journals and other literature revealed only a few reported incidences of
copper failures in residential building 4,5. This may be due to copper’s satisfactory performance
under most conditions.
One study4 conducted for the Washington (DC) Suburban Sanitary Commission indicated an
unusual failure mechanism in underground copper pipe. In this situation, one-inch copper pipe
had been installed for the water service to homes. The copper was sleeved at sections where it
approaches or crosses a sanitary sewer using two-inch or three-inch corrugated plastic drain pipe.
An analysis of three failed water supply pipes showed a series of uniformly spaced cavities. The
spacings of the cavities matched that of the corrugations in the sleeve. The report’s author, based
on electron microscope examination results, suggested that a number of corrosion mechanisms
were operating. However, it was apparent that the primary mechanism involved small vibrations
in the copper pipe that continually destroyed the protective cuprous oxide cover at each point of
3Guerrera, A.A., ”Grounding of Electric Circuits to Water Services: One Utility Company’s Experience,” Journal
AWWA, February 1980.
‘DeRonja, F.S., “Investigation of Failed Copper Water Service Lines,’’ for Washington Suburban Sanitary
Commission, April 1990, (unpublished).
5Woodside, R.D., Waters, F.O., and Cornet, I., “Corrosion and Other ProbIems in Copper Tubing in Some
Southern California Housing Tracts,” Proceedings of the Third International Congress on Metallic Corrosion,
Moscow, 1969.
2
contact with a corrugation. This created a situation where other mechanisms, most likely
aggressive water, quickly corroded the copper pipe.
FLORIDA INSTALLATIONS
The plumbing installations were similar in each of the homes under investigation in Florida. All
of the homes are built on concrete slab-on-grade foundations. A polybutylene water service runs
from the public supply up to the foundation. All of the remaining water supply plumbing is
copper. Sub-slab water supply pipes are type L copper enclosed in a continuous plastic sleeve.
There are no joints in the sleeve below the slab. The sleeve terminates just above the floor slab.
The joint between the sleeve and copper is typically caulked at some point during construction
with a commercial caulking compound.
Because the fit between the 3/4-inch I.D. sleeve and the 1/2-inch copper is tight, the copper is
frequently lubricated prior to sliding it through the sleeve. Dishwashing liquids and other
commercially available soaps are used as the lubricants, although specific soaps were ‘not
identified.
METALLURGICAL INVESTIGATION
Research Center staff did not have the opportunity to observe any of the failures directly since
they were repaired as soon as they were detected. None-the-less, two samples of failed pipe
retained by the builder were obtained and analyzed for possible causes of failure.
The first set of samples was forwarded to the Copper Development Association (CDA) in
Greenwich, Connecticut. The second set was analyzed by Forensic Metallurgy Associates
(FMA), a private forensics service in Springfield, Virginia. Follow-up tests were conducted by
FMA on three soil samples taken from the area near the reported failures: one sample of fill
material that is used to surround the sub-slab plumbing, and two samples of native soil. Results
of each analysis are included in the Appendix.
3
RESULTS
Results of the independent laboratory investigations were similar. Both concluded that the
corrosion was due to contact between the copper pipe and an aggressive solution, possibly
containing chloride and sulfate ions. Potential sources of the water for the solution include
groundwater or surface water that entered the sleeve during construction or condensate that
accumulated after construction.
Soil test results indicated that all three samples had a pH of 8.1 and contained carbonate
minerals. The presence of moisture, an alkaline pH, and carbonate minerals will cause corrosion
of copper. Sulfate and chloride ions in solution can also cause corrosion of copper. However,
neither of these were present in appreciable amounts in the soil.
RECOMMENDATIONS
It is apparent that the protective sleeve serves as a collection point for water that combines with
aggressive minerals in the soils, leading to corrosion that creates a failure in the copper. Where
local experience indicates that a sleeve is necessary with copper pipes, it may be appropriate to
use an alternative pipe material or to install the sleeve with the following recommendations:
The sleeve should be one continuous section. Joints should be avoided, but if used, they
should be watertight.
The sleeve should be capped at its ends until the copper is installed to prevent water from
entering during construction.
Flexible couplings or caulking may be used to close the gap between the copper and the
sleeve.
The sleeve and copper should be free of soil particles and other foreign substances that
could combine with condensate or moisture from other sources and attack the copper.
4
Further investigation should be considered to identify the extent of these types of failures and to
collect additional data that could more firmly support these recommendations. Additional
investigation should also address whether the benefits of sleeving the copper outweigh the
potential problems the sleeve may cause. For example, in well-drained soils, it may be possible
to install the sub-slab copper directly in the soil.
5
APPENDIX A
Failure Analysis
COPPER TUBE/FITTING SPECIMEN
MULTICON SOUTHEAST, INC.
DAVIE, FLORIDA
COPPER WATER TUBE/FITTING SPECIMEN
MULTICON SOUTHEAST, INC.
DAVIE, FLORIDA
Background
In August 1991, Mr. A.G. Kireta, Regional Manager for the Copper
Development Association (CDA) in the eastern states submitted a
copper water tube/fitting specimen to the CDA office in
Greenwich, Connecticut for laboratory examination. The specimen
consisted of a 29.1-inch length of 0.5-inch diameter (nominal
size) Type L copper water tube with a copper coupling soldered to
one end which was, in turn, soldered to a 197.5-inch length of
Type L capper water tube. It had been removed from a domestic
water line, under-the-slab, at an unidentified residence
constructed by Multicon Southeast, Inc., Davie, Florida.
According to the information furnished, the specimen was
representative of other, under-the-slab, tubes which had
developed leaks in time periods ranging from six months to four
years. It was also reported that all of the leaking copper
tube/fitting sections had been located inside polyethylene
tubes/sleeves (i.e., in accordance with state codes).
Results
Examination of the outside surface of the specimen revealed
several areas of severe pitting attack (e.g., see the encircled
areas in Figure 1). The corrosion-induced pits contained porous
reddish-brown cuprous oxide (Cu2O) which was typically overlaid
with some green colored copper corrosion products (Figure 2).
Stereomicroscopic examination revealed that one of the corrosioninduced
pits had propagated through the tube wall (i.e., see
encircled area on the third tube section from the top in Figure
1).
type perforation had initiated on the outside surface of the
tube.
Energy dispersive spectroscopy (EDS) and microchemical analysis
(MCA) revealed that the green colored copper corrosion products
associated with the pitting attack contained major quantities of
copper, minor amounts of chloride and sulfur (as sulfate), semiminor
quantities of calcium and trace amounts of silicon. The
green colored copper corrosion products consisted primarily of
copper chloride(s) and copper sulfate.
It was clearly evident that the nearly-microscopic pinholeFigure
1 – SECTIONS SHOWING THE REPRESENTATIVE OUTSIDE
SURFACE OF THE UNDER-THE-SLAB COPPER WATER
TUBE/FITTING SPECIMEN FROM DAVIE, FLORIDA
Several areas of localized pitting attack existed
on the outside surface (e.g., see encircled
areas).
propagated through the tube wall (i.e., see
top)
One of these corrosion-induced pits had
encircled area on the third tube section from the
(Magnification: 0.6X)
Where pitting attack had not taken place on the outside surface,
there was no significant deterioration by the external
environment. Basically, the copper in these essentiallyunaffected
areas was covered with a protective tarnish film of
reddish-brown cuprous oxide. At: several locations, the cuprous
oxide was overlaid with a thin friable layer of somewhat looselyadherent
green colored copper corrosion products (e.g., see the
second tube section from the top in Figure 1) which appeared to
have been deposited on the outside surface by the evaporation of
water which had been transported from pit sites.
The total specimen was subsequently sectioned lengthwise in order
to examine the inside surface.
Examination of the inside surface revealed no significant
deterioration by the water conveyed. In general, the inside
surfaces of the tubes and fitting were covered with a protective
tarnish film of reddish-brown cuprous oxide.
colored copper corrosion products existed on the waterside
surface, no major pitting attack had occurred to the underlying
copper. It was clearly evident that these longitudinallyoriented
corrosion products were soldering flux-related. For
example, green colored copper corrosion products were observed to
be associated with an 11-inch long sticky petrolatum-base
soldering flux-run which existed at one location on the inside
surface.
Where pitting attack had not taken place on the outside surface,
micrometer caliper measurements revealed that the tubes on the
specimen still satisfied the wall thickness requirements of
American Society for Testing and Materials (ASTM) Standard
Specification B88 for Seamless Copper Water Tube. The wall
thicknesses varied between 0.036 and 0.037-inch which is typical
for 0.5-inch diameter Type L copper water tube. Similarly, the
coupling still satisfied the wall thickness requirements of
American National Standard ANSI B16.22-1980 for Wrought Copper
and Copper Alloy Solder Joint Pressure Fittings.
Based upon examination of the specimen submitted for laboratory
investigation, it can be concluded that the cause of the pinholetype
perforation through the tube wall was corrosion-induced
pitting attack which had initiated on the outside surface.
Although some soldering flux-initiated corrosion had taken place,
there was no significant deterioration on the waterside.
Although some green
Figure 2 – HIGHER MAGNIFICATION VIEW SHOWING REPRESENTATIVE
CORROSION-INDUCED PIT SITES ON THE OUTSIDE SURFACE
OF THE SLEEVED SPECIMEN FROM DAVIE, FLORIDA
The corrosion-induced pits on the outside surface
contained porous reddish-brown cuprous oxide which
was typically overlaid with some green colored
copper corrosion products.
(Magnification: 2X)
Conclusions
The only viable explanation for the external corrosion was
localized areas of moisture/water w h i c h had collected and
concentrated inside the polyethylene tube/sleeve. The source of
the water was possibly groundwater which had seeped. into the nonmetallic
tube. Alternatively, the polyethylene tube may have
collected water during construction of the residence. Regardless
of the source of the water, aggressive chloride and sulfate ions
in the aqueous environment initiated and supported the pitting
attack. The source of the chloride ions could have been the
groundwater. Alternatively, their source could have been the
concrete used to form the slab. Most likely, the source of the
sulfate ions was the groundwater.
Recommendations
When non-metallic sleeves/tubes must be placed around copper (or
other metallic) tubes/fittings, the installation practice must
preclude the ingress of moisture/water. For example, the ends of
tubes must be appropriately sealed. The tubes/sleeves must also
be free of moisture/water when the copper tubes/fittings are
inserted.
Preferably, copper water tubes/fittings should be placed in
underground environments without tubes/sleeves because the use of
these ”shielding” devices precludes the use of cathodic
protection for corrosion mitigation in those very-rare instances
where the soil/groundwater is aggressive to copper.
Additional information on the underground corrosion of copper and
the cathodic protection technique for mitigating this
deterioration is presented in the paper “Conditions Contributing
to Underground Copper Corrosion.” A copy of this paper is
included ‘in the Appendix.
September 18, 1991
JRM/AC/jm
157/
FLORIDA INSTALLATIONS
The plumbing installations were similar in each of the homes under investigation in Florida. All
of the homes are built on concrete slab-on-grade foundations. A polybutylene water service runs
from the public supply up to the foundation. All of the remaining water supply plumbing is
copper. Sub-slab water supply pipes are type L copper enclosed in a continuous plastic sleeve.
There are no joints in the sleeve below the slab. The sleeve terminates just above the floor slab.
The joint between the sleeve and copper is typically caulked at some point during construction
with a commercial caulking compound.
Because the fit between the 3/4-inch I.D. sleeve and the 1/2-inch copper is tight, the copper is
frequently lubricated prior to sliding it through the sleeve. Dishwashing liquids and other
commercially available soaps are used as the lubricants, although specific soaps were ‘not
identified.
METALLURGICAL INVESTIGATION
Research Center staff did not have the opportunity to observe any of the failures directly since
they were repaired as soon as they were detected. None-the-less, two samples of failed pipe
retained by the builder were obtained and analyzed for possible causes of failure.
FREE ESTIMATES
Jacksonville Duval County 904-346-1266
St Augustine St Johns County 904-824-7144
Orange Park Clay County 904-264-6444
Jacksonville Beaches Duval County 904-246-3969
Fernandina Nassau County 904-277-3040
Macclenny Baker County 904-259-5091
Palm Coast Flagler County 386-439-5290
Daytona Volusia County 386-253-4911
GAINESVILLE ALACHUA COUNTY 352-335-8555
Serving all of Florida and Georgia at 904-346-1266
EMAIL LARRY@1STPROP.COM (feel free to email your bidding packages here)
Introduction
The hot and cold potable water distribution piping in the typical U.S. residence is generally of little concern to the homeowner or apartment resident. Hidden behind walls, ceilings, floors and cabinets, it is mostly out of sight, and fortunately is rarely a problem. The most common domestic water problems encountered are dripping faucets, sticking or leaking toilet tank valves and occasionally a water heater that ceases to work properly. These are nuisance problems that most every homeowner has experienced at least once. By comparison, more serious and damaging water supply problems associated with pipe leaks are far less common. When they do occur, however, leaks can result in extensive water damage if not immediately detected, and often expensive repairs.
What are the principal causes of water pipe failures and can the average home owner detect potential problems before they become serious? There are a number of factors that affect the performance and service life of water pipe, or tube, that must be considered: (1) the size and type of pipe, or tube, material installed, which in a U.S. home is most likely copper, but may also be galvanized steel or plastic pipe, such as PVC/CPVC or polybutylene, (2) the design and workmanship of the installed piping system, (3) the quality, or corrosiveness, of the water conveyed in the pipe, and (4) the current age of the pipe. Each of these factors must be considered when evaluating the current condition, or the cause of leaks, in a home water piping system. The following discussion is intended to provide basic information for the homeowner about the known causes of plumbing failures and leaks.
Background
Although water piping in homes may be any one of the several materials mentioned above, market data surveys by the Copper Development Association (CDA) [1] confirm that copper is the predominant material selected for domestic water service and distribution in residential construction. Water service is defined as the pipe from the meter or main to the building, and distribution as the water plumbing within the building. Copper became a popular choice for water distribution plumbing in the U.S. following World War II, but had been available since the 1920’s with the advent of solder fittings for joining pipes [2]. Market data compiled and published by the CDA in the early 1980’s reflecting the production and sale of copper water tube reported more than half a billion linear feet of copper water tube installed annually [1]. By 1994, that amount had increased to about one billion linear feet per year in U.S. water service and distribution systems [3]. This accounts for more than 80% of the total water distribution pipe installed in residential construction. The continued high volume usage of copper tube for hot and cold water plumbing is indicative of the problem free performance obtained by most homeowners.
A useful starting point for examining the use and performance of copper tube for water distribution is the material itself and the methods of installation. Practically all copper tube for water service is manufactured according to American Society for Testing and Materials (ASTM) standard B88, Standard Specification for SEAMLESS COPPER WATER TUBE [4]. This nationally recognized standard, first published in 1932, defines the product forms, chemical composition, dimensions, tolerances and overall quality of the finished products. Copper tube dimensions are specified according to a nominal diameter for which the outside diameter of any size from 1/4 inch to 12 inch is one-eight inch larger than the nominal diameter. Of interest to the home owner is the fact that copper tube is available in two product forms, hard drawn straight lengths and soft annealed coils.
Each product form is manufactured in three types. The primary difference in the three types is wall thickness, with Type K having the thickest tube wall, Type M the thinnest, and Type L having an intermediate thickness.. For example, a very commonly used standard size in home plumbing, 2 inch, is 0.625 inch outside diameter. In Type K, 2 inch tube has a specified nominal wall thickness of 0.049 inch, compared to only 0.028 inch nominal thickness for Type M.
Hard drawn straight lengths of tube are required to be identified by the manufacturer with stenciled markings along the length of the tube in green for Type K, blue for Type L and red for Type M; no markings are required on soft annealed coils. By inspection of new tubing, one should be able to readily identify the manufacturer, country of origin and size and type of copper tube provided. Those markings can deteriorate and become difficult to read, however, as installed tubing ages.
Nationally recognized plumbing codes, plus local jurisdiction construction codes and ordinances, are combined in any locale to specify and regulate acceptable practices for installation of plumbing by licensed contractors. Proper construction and installation of copper water plumbing is highly dependent on the skill and workmanship of the plumbing contractor in assembling and joining copper tube to the fittings and valves necessary to construct a distribution system. Soldering is the most widely approved method employed. ASTM B828, Standard Practice for Making Capillary Joints by Soldering of Copper and Copper Alloy Tube and Fittings [5] defines, and describes in detail, the correct procedures to consistently make satisfactory joints.
Copper Corrosion Resistance and Performance
Documented incidents of leaks in copper water tube are rare when compared with the total amount of copper water tube installed in the U.S. homes and apartment buildings [1]. With few exceptions, the leaks originate on the inside (waterside) tube surface. The process responsible for the formation of leaks is corrosion, defined for practical purposes as oxidation and consumption of metal. All metals and alloys of commercial importance, including copper, but with the exception of the precious metals such as gold and platinum, will naturally revert from their metallic form to an oxide if exposed to the proper conditions. Copper alloys are relatively corrosion resistant by virtue of protective films that form as the copper ages. The darkening of a new copper penny, or the gradual formation of a blue-green (verdigris) patina on ornamental copper objects exposed out-of-doors, are examples of protective film formation on copper that most everyone is familiar with.
Plumbing system engineers and designers most often select copper because of its history of good performance. A conservative service life of 20 years is generally assumed for design purposes, but an actual life of 25 to 30 years, and more in some areas of the U.S., is usually obtained. Achieving a long, problem free service life from copper water tube is dependent upon the formation of a uniform, protective film on the inside of the tube. A slow rate of uniform corrosion that begins when water containing dissolved oxygen is first introduced into the plumbing system is responsible for formation of the protective film. Depending upon the source of water and water treatment, the film is a mixture of copper oxides and calcareous mineral scale. The protective film creates a barrier between the metal surface of the tube and the flowing water. As the protective film develops during the initial few months of use, the corrosion rate decreases from an initial value of 0.001 to 0.003 inch per year on the clean metal surface to a long term average rate of 0.0003 inch per year. The long term corrosion rate value, according to the American Water Works Association [6], is typical for copper tube in potable waters containing dissolved oxygen and a pH between 7.0 and 9.0. Any physical or chemical condition that interferes, however, with the initial film formation process, or results in damage to the film, can cause accelerated pitting type corrosion and short term failure of the copper tubing. Short term failures generally occur within 1 to 6 years of placing the plumbing system into service [6, 13].
In response to environmental concerns about water quality in general, and drinking water specifically, the U.S. Environmental Protection Agency (EPA) was empowered by the U.S. Congress with oversight and enforcement responsibilities in the Safe Water Drinking Act (SWDA) of 1973 [7]. Amendments were passed in 1986 [8] that further defined water quality requirements, and eliminated the use lead in solders for joining copper tube. In 1991 [9], Congress further amended the SWDA placing maximum contaminant level (MCL) restrictions on the amount of lead and copper that could be present in public utility supplied drinking water. Commonly referred to as the ALead and Copper Rule,@ procedures were defined in the amendment that require utilities to monitor and report the quality of water provided, and the actions to be taken if the water fails to comply with the MCL requirements. Water quality reports published by the public utilites, as required by the USEPA and the SWDA, can be obtained by the home owner. They provide information useful in judging the quality of potable water delivered to their homes and the effect that water likely has on their copper plumbing.
Corrosion Failures: Causes
Published accounts of copper water tube failure investigations and research studies [1,2,3,6,11,12,13,14,16] during the past more than 40 years have identified several design, installation and water chemistry conditions that have been found responsible for the occasional failures. Water is the essential element to any internal tube or pipe corrosion problem, but there are several design, installation and initial operation factors that can be the primary cause of leaks and failures.
Water Chemistry Effects
The source of raw water and the treatment methods applied by public utilities to produce potable water for distribution to it=s customers determines the taste, odor and corrosiveness of the finished water. Raw water sources vary dramatically across the U.S. A primary distinction is made between surface water collected in reservoirs from rain or snow-melt, or from rivers, and well water pumped from underground aquifers.
Surface Water Sources
Surface waters from rivers and lakes usually have a total dissolved solids content less than 100 milligram per liter (mg/l) and are characterized as soft (calcium and magnesium content less than 50 mg/l) and low in alkalinity (total amount of bicarbonate, carbonate and hydroxide less than 50 mg/l) [15]. These values are very general, and significant variations exist for different geographic areas of the U.S. In the Pacific northwest, for example, the principal raw water source is surface water from snow-melt which has a total dissolved solids content of 30 mg/l, or less, is very low in alkalinity and hardness, and is highly acidic.
For reference, acidic implies a pH of less than 7.0. A neutral pH is defined as 7.0, which is neither acidic nor basic. At a pH less than 7.0, soft low alkalinity surface water can promote unacceptably high corrosion rates on copper plumbing. Besides complaints by customers of green staining of porcelain plumbing fixtures, improperly treated water can lead to violations of the SWDA Lead and Copper Rule. Corrosive water of this type must be treated with lime, soda ash or caustic soda to increase the alkalinity and raise the pH above 7.0, which effectively prevents general corrosion of copper plumbing [2,6].
Raw surface waters generally require treatment to remove suspended matter. A flocculating agent, such as alum (aluminum sulfate), is added to promote coagulation of the suspended matter for removal in sedimentation basins at the treatment plant. For many surface waters, filtration is also necessary for sediment removal. Carry over of suspended material and alum in the finished water can occur, however, and has been identified in some case histories [11] as a contributing factor in preferential pitting of hot water copper tubing. Deposition of aluminum hydroxide, and other materials such as manganese dioxide and hydrated hematite (iron oxide), on the surface of copper tubing have been identified as pitting agents in hot water plumbing.
Groundwater Sources
The most widely publicized corrosion problems with copper plumbing [1,2,3,14] have occurred in treated and untreated water pumped from wells. Groundwater, as compared to surface water, is generally hard and alkaline, with a total dissolved solids content of 200 to 300 mg/l, or higher. Significant amounts of dissolved carbon dioxide are often present in groundwater, which if not properly treated, can be extremely aggressive to copper tube. The effect is most commonly referred to as Acold water pitting,@ and is characteristically observed in cold water plumbing, but not in hot. Pitting under these conditions is less sensitive to the effect of gravity, and as a rule, does not occur preferentially on the bottom of horizontal tubing, but rather, is distributed around the entire inside surface of the tube. Cold water pitting can be very aggressive, penetrating the tube wall in a relatively short time, but usually within three to four years after being placed in service. The frequency of leaks typically decreases after five years, and is rarely observed after 15 years or more.
Pitting is almost always associated with hard well waters with pH values in the range from 7.0 to 8.2 [2]. NACE publication TPC No.7 [12] describes well waters having pitting tendencies are characterized by a pH of less than 7.8 and containing more than 17 milligram per liter (mg/l) of carbon dioxide. Well waters treated to raise the pH to 8.0, or above, to remove dissolved carbon dioxide are generally rendered non-corrosive to copper. Aeration is also an effective means of removing dissolved carbon dioxide, and has the added benefit of stripping dissolved hydrogen sulfide from the water, when present. Well waters in some areas of the U.S. contain hydrogen sulfide which not only causes an offensive odor problem, but also promotes cold water pitting of copper water tube. Treatment schemes to remove hydrogen sulfide generally rely on a combination of chlorination and aeration.
FREE ESTIMATES
Jacksonville Duval County 904-346-1266
St Augustine St Johns County 904-824-7144
Orange Park Clay County 904-264-6444
Jacksonville Beaches Duval County 904-246-3969
Fernandina Nassau County 904-277-3040
Macclenny Baker County 904-259-5091
Palm Coast Flagler County 386-439-5290
Daytona Volusia County 386-253-4911
GAINESVILLE ALACHUA COUNTY 352-335-8555
Serving all of Florida and Georgia at 904-346-1266
EMAIL LARRY@1STPROP.COM (feel free to email your bidding packages here)
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