 Copper Water Supply Piping & Copper Drain Piping
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Copper plumbing, copper supply & copper drain pipes: this article lists our in-depth articles on inspecting, testing, and repairing problems with copper plumbing: water supply and drain waste vent piping, plumbing traps, piping materials, clogged or noisy pipes, and types of pipe hazards or product defects. The articles at this website will answer most questions about water supply & drain piping, wells, & water tanks as well as many other building plumbing system inspection or defect topics.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Copper Building Water Supply & Drain Piping
Types of Copper Piping used in buildings
Other types of copper building piping systems are discussed at GAS PIPING, VALVES, CONTROLS and at OIL TANK PIPING & PIPING DEFECTS.
Our page top photograph shows a remarkable method used by a homeowner to handle leaks at a poor solder joint on copper water supply piping.
Our photograph of copper water supply piping (left) tells us that this is a cold water supply line located in a humid or wet crawl area - notice the condensation on the piping? More about "sweating" cold water pipes is at CONDENSATION or SWEATING PIPES, TANKS.
The following summary notes about copper and other types of building piping are from Carson Dunlop Associates' Home Reference Book, used with permission:
Copper piping has been used extensively since the early 1950s for supply lines from the city main to the house as well as for in-building water supply and drain piping.
Copper water supply piping is typically 1/2 or 3/4 inch diameter. Copper piping is typically 1/2 or 3/4 inch diameter. Copper piping has soldered connections and the walls of the pipe are thinner than galvanized steel. Copper piping has soldered connections and the walls of the pipe are thinner than galvanized steel.
From 1950 to 1970, 1/2-inch diameter piping was used commonly for residential building water supply pipes. After 1970, 3/4-inch diameter copper service piping has been more common for building water supply piping.
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Guide to K, L, and M and Other Types of Copper Pipes used in Buildigns: life expectancy, izes, thickness, durability & uses
The life expectancy of
copper piping is dependent on water conditions.
In many areas, its life expectancy is indefinite. In harsh corrosive water or corrosive soil conditions, it may fail within 20 years or even less.
Occasionally manufacturing defects also result in early failure of copper building piping. We discuss water pH, acidity and corrosiveness at Copper Piping FAQs below.
Carson Dunlop Associates' sketch (left) illustrates three types of copper piping used in buildings for water supply or drains. In order of thickness, from thinnest to thickest pipe walls, read Types M, L, or K copper.
- Type M copper piping is used for general plumbing, above ground. Type M copper tubing walls are the thinnest used in construction, at 0.026" in wall thickness and thus more vulnerable to leaks if water being handled is aggressive or corrosive. Type M copper is color coded with red markings. We illustrate both red and embossed-in-copper markings on copper piping in our photo below.
- Type L copper piping is also used for general plumbing as well as for heating system piping. Type L copper tubing walls are thicker, at 0.040". Type L copper piping is color coded with blue markings. Type L copper is intended for use in domestic water supply piping, fire protection systems, solar installations, fuel and fuel oil piping, HVAC systems, and snow melting systems. Unlike M-copper, Type L copper may be used for natural gas or LP gas piping in some jurisdictions and locations.
- Type K copper piping is used for plumbing, heating, gas lines, and underground, and has a wall thickness of 0.049". Type K copper piping is color coded with green markings. K-copper is intended for use with domestic water supply piping, fire protection piping, solar applications, fuel or fuel oil piping, HVAC applications, and snow-melting systems.
- Flexible copper tubing used as water piping: Flexible copper tubing can be bent around corners using special tools. This is not common since it is more expensive and can be awkward to work with in close quarters. Flexible copper tubing is also used for oil piping (OIL TANK PIPING & PIPING DEFECTS) and natural gas piping (GAS PIPING, VALVES, CONTROLS).
- Copper tubing used in heating baseboards varies in thickness and durability depending on the manufacturer and product line.[7]
- Drain-waste-vent DWV copper piping is color coded yellow.
- Refrigeration system copper piping used for air conditioning and some gas piping applications is color coded blue.
- Medical gas distribution copper piping (in types K or L) is marked OXY/MED, OXY, MED, OXY/ACR or ACR/MED and is intended for medical gas use.
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Dimensions, Sizes, Thickensses, Lengths of Copper Piping
How is Copper Piping Sold: lengths, diameters
Copper piping is sold in nominal or standard sizes in straight lengths of 12 ft. 18 ft. or 20 ft. from 1/4" diameter all the way up to 12-inches in diameter, depending on the copper type, thickness, grade, and intended application. Copper piping from 1/4" up to 2-inch in diameter is also sold in coils of 45' up to 100 ft. depending on the pipe diameter.
What is the Relationship Between Nominal Copper Pipe Size and its Actual Physical Size?
Plumbing Copper:
Copper piping discussed here and used for plumbing is 1/8" larger in diameter than its nominal diameter. So a 1/2" copper pipe will actually measure 5/8" in thickness. The actual internal diameter of a copper pipe will vary depending on the thickness of the pipe wall, even though these outside dimensions remain the same. For example, because K-copper has a thicker tube wall than Type M copper, a 1/2" K-copper pipe will have a slightly smaller inside diameter than a 1/2" L or M copper pipe.
Refrigeration Tubing Copper
Unlike copper used for plumbing (above), copper tubing used for HVACR (heating, ventilating, air conditioning & refrigeration systems), is sold in sizes that correspond to the actual outside diameter of the tubing.
What are the Standards for Copper Piping Sizes & Thickness
The copper content of copper piping meeting the ASTM standards below is virtually pure copper - or 99.9% Cu. The copper is shiny when purchased, typically having had any exterior or interior surface oxidants cleaned off using phosphorous. If you hear reference to DHP copper or C122 coppeer, this is the product being described.
The four most-relevant standards for copper pipe thickness and dimensions depend on the intended application and use and are listed as follows:
- ASTM Standard Classifications B-698 encompasses six plumbing pipe (or "tube") standards including ASTM-B88.
- Type K copper and Type L and M copper pipes are governed by Standard: ASTM B-88
- Type DWV copper piping is governed by Standard: ASTM B-306. This standard also applies to copper pipes used in solar energy and other HVAC applicaitons.
- Type ACR copper piping intended for use in air conditioning and refrigeration sytsems and also for natural gas or LP gas (LPG gas) is governed by Standard: ASTM-B-280. [K, L, or M Copper tubing is not allowed for natural gas distribution.]
- Type OXY/MED copper piping intened for use in medical gas applications is governed by Standard: ASTM B-819
Compression Fittings for Copper Tubing Connections
Flexible copper tubing is usually joined to additional tubing sections or to other plumbing fittings by either compression fittings or flare fittings, depending on the application.
For example, compression fittings (photo at left, from Wikipedia) are sometimes used on copper water piping where soldering is difficult or inconvenient, but these are not used on copper gas or oil lines where flare fittings may be applied instead.
Flare fittings and compression fittings are intended for use on soft-temper copper piping and tubing. In addition to flare and compression fittings there are also other mechanical connectors that now work with soft or hard copper that do not require soldering.
Watch out: compression fittings are very convenient and easy to install on copper pipes or copper tubing, but if you fail to de-burr a freshly-cut copper pipe or tube, properly ream out the interior opening, or if you over-tighten the coupling during installation you may crack the brass or copper ring, leading to leaks at the connector.
Compression fittings are used with K-copper. K copper pipes and tubing can also be joined or connected using flare fittings and sweat fittings discussed below. |
Flare Fittings Used for Flexible Copper Tubing Connections
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 Flare fittings used on flexible copper piping and their leaks and defects are discussed at GAS LEAK DETECTION, LP / NG and Gas Piping Defects. Using a special flaring tool the soft copper tubing or piping is actually spread open or flared at its end in order to mate with the female end of the flare fitting connector shown in our photograph.
Watch out: defects in flare fittings used on flexible copper tubing can result in gas leaks out of gas piping, and in the case of oil piping such as for oil-fired heaters, flare fitting defects result in both oil leaks out of the system and air leaks into the system. Air leaks into oil piping in turn lead to improper oil burner operation and even potentially dangerous conditions. Flare fitting defects include:
- Improperly made tubing flares that are too small
- Improperly made copper tubing flares that are cracked
- Scratches or gouges on the copper tubing flare or on the brass flare fitting (shown in our photo, above left)
Seat and flare fittings are permitted on K and L copper. LP gas tubing. These fittings are not used on refrigeration equipment. |
Swaged Copper Tubing Joints
Soft copper tubing can also be joined by using a swaging tool that expands the open end of one of the tubes to be joined so that its mate can be inseted into the enlarged opening, and the result sealed by soldering or brazing.
This is a common procedure when using air conditioning refrigerant tubing because of the high pressures that may be involved and the need for extra strong resistance to leaks in piping that may be subject to wide temperature variations as well as mechanical vibration.
Our photo (red arrow in photo at left) illustrates swaged fittings on copper tubing - you can see the swaged tubing joints at the left and right ends of the gray filter-dryer on this air conditioning high pressure refrigeration line exiting at the bottom of a compressor-condenser unit.
A swaging tool is inserted into the end of the copper tube and hammered inwards. As the properly-calibrated diameter of the swaging tool is forced into the copper tube, the copper expands to just the right size to accept the outer diameter of the mating section to be inserted. For example, if we are swage fitting two sections a 3/8" nominal diameter copper tube together, the swaging tool will enlarge the receiving copper tube section so that its inside diameter will accept the 3/8" outer diameter of the un-treaterd tube to be joined.
Usually we work the swaging process on tubing at ambient temperatures but some procedures call for pre-heating the copper to make it easier to expand.
Watch out: Soft copper tubing is drawn copper while hard tubing is annealed. It's easy to swage fit soft copper, usually. But if copper tubing has been repeatedly bent, that process may have annealed the copper somewhat, making it difficult to form either a flare fitting or a swaged fitting without cracking the tubing. Copper tubing may also become crack prone when exposed to mercaptan or other odorants in LP gas or natural gas. Moisture exposure and even some types of solder also can affect its susceptability to cracking later. For these reasons copper tubing is not allowed for natural gas distribution.
Sweat Fittings for Copper Pipes & Tubing
"Sweat" fittings or "soldered fittings" for copper piping refer to the traditional and perhaps most widely-used method for residential copper suppy and drain pipe connections, bends, elbows, valves, and similar fittings in buildings.
Depending on the connection required, a coupling (straight connection), 90 degree ell, 45 degree ell, tee, and even fittings that marry copper pipes of different diameters are soldered to the copper tubing or pipe to make the connection.
Sweat fittings may themselves be made of copper tubing that has been formed by machine, or from cast or milled bronze.
Table of Types of Copper Pipe or Tubing Connections, Connectors, Fittings |
| |
Sweat Fittings |
Swage Fittings |
Flare Fittings |
Compression
Fittings |
| K copper |
ok |
|
ok |
ok |
| L copper |
ok |
|
ok |
ok |
| M copper |
ok if annealed
ok if drawn-tempered |
|
ok |
ok if annealed |
| Flexible copper tubing - water |
ok if annealed
ok if drawn-tempered |
? |
ok |
ok if annealed |
| Flexible copper tubing - LPG |
|
? |
ok |
|
| Flexible copper tubing - HVAC refrigerants |
ok |
ok |
|
|
| |
|
|
|
|
Notes to the table: [this table is incomplete, other citations needed - ed.]
Standard: Copper Tubes, ASTM B-88M |
How to Tell Brass Water Pipes from Copper Piping
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 Watch out: on older buildings brass water supply piping may have been used, and may be at or near the end of its useful life. It can be tricky to tell the difference between brass water supply piping and copper water supply piping if you are not experienced with these materials, as their colors are similar, especially when both types of piping have become an oxidized brownish color with age.
Both brass and copper are non-magnetic, so they won't respond to a "magnet" test to look for iron or steel.
Brass water supply piping, unlike copper, is a thicker material that is usually joined by threaded fittings of the same size and pipe thread specifications (NPT) as iron and galvanized iron piping.
Usually, brass piping is also so rigid that it is not bendable. Or not very bendable anyway. So in our photograph (left) of water supply piping at a bath tub in an older home, the larger-diameter left-hand pipe is surely brass, connected to a galvanized iron fitting at its bottom end. The right-hand vertical pipe may be copper tubing as is the darker copper pipe at left behind our brass one.
Don't worry about that odd little machine in bottom center of the photo - we were collecting an air sample in this wall cavity.
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Copper Supply or Drain Pipe Pinhole Leaks: cause, cure, prevention
Water chemistry, Electrical Grounding, Netural Wiring, & Copper Pipe Pinholing & Leaks
In a building where leaks are found recurrent in copper piping there are several possible explanations:
some possible causes for the pinhole leak in copper water piping under your building slab.
- Defective copper piping: the pipe could have been defective from day one, e.g. with thin spots or damage that corrode through and leak
- Improper type of copper piping may have been installed - see the copper piping types and applications described in the article above.
- Damaged copper water piping: the pipe could have been damaged in transport or installation or even during the slab pour
- Improper electrical ground or neutral wiring: on occasion a bad or improperly-connected electrical ground or another electrical problem can contribute to plumbing or other pipe corrosion at a building. In diagnosing recurrent failures in a ground water sourced air conditioning system that kept blowing out a very expensive cooling coil for we found that the problem was finally traced to unanticipated electrical currents in the ground system due to a neutral wiring error in the AC unit's controls.
Ask a licensed electrician check the home's grounding and neutral systems: that they are properly wired, that the grounding electrodes are properly sized and installed, and that there are no stray currents on the neutral system nor shorts or leaks in the wiring system (an AFCI or GFCI can help detect thee too).
- Aggressive water: the water chemistry itself can be a source of metal water pipe (and even drain pipe) corrosion.
If the pH is low <6.0, the hardness low generally<50ppm, the alkalinity low generally <40ppm, the water could be considered
extremely “soft” and aggressive to the home’s metallic plumbing system. If the
chlorides are elevated >100ppm this would only compound the problem. The
water should be treated to make the water less aggressive by raising the pH, alkalinity or hardness. - CT DOH.[1]
If the pH is low <6.0, the hardness low generally<50ppm, the alkalinity low generally <40ppm, the water could be considered
extremely “soft” and aggressive to the home’s metallic plumbing system. If the
chlorides are elevated >100ppm this would only compound the problem. The
water should be treated to make the water less aggressive by raising the pH, alkalinity or hardness.
Also see Acidic water & copper pipe corrosion/leak risk discussed below
Summary of the issue around grounding building water piping
Many sources, including the Connecticut DOH have pointed out a long-standing disagreement & confusion about the reasons for grouinding building water supply piping. For example
AWWA opposes the grounding of electric
systems to pipe systems conveying drinking water to a customer’s premises. ... AWWA asserts that a water utility has no direct or indirect responsibility in connection with the installation of water pipe grounding systems or for the maintenance of the integrity of any grounding attachment or connection made
to a water pipe system. [AWWA 5/15/2003] [1]
This statement is a bit of a red herring. Water and some plumbing associations are concerned about building owner complaints about metal water supply pipe corrosion and leakage that might be traced to or blamed on the electrical grounding of those systems. Wishing to avoid those complaints the industry, under the aegis of warning that water suppliers can't be responsible for the failure of such an electrical ground [a valid caveat] a warning is issued that also gives relief for metal piping leaks caused by a variety of other problems such as
- water chemistry - see our notes just below
- defective piping
- improper installations
More to the point, metal water piping is grounded not to provide an electrical ground for the building (we agree completely that water piping as a ground is unreliable for many reasons, (such as inclusion of non-conductive plastic piping, diaelectric fittings, water meters, etc). Metal water piping is bonded to a building ground system as an important safety precaution to protect building occupants from electrocution hazards should live electrical wires or components come in contact with buidling piping, faucets, fixtures, etc.
In a properly-wired building, the grounding conductor and bonding system do not normally carry current, and would not be blamed for copper pipe pinholing etc. The grounding system is intended to conduct electrical current only in the event of a fault or emergency [such as a lightning strike or a hair dryer dropped into the bath tub or sink].
Details about the code requirements and reasons for grounding metal water piping are at WATER PIPING GROUND BOND
How to Check for Electrical System Problems that Corrode Copper Water Pipes
[For buildings served by private well water] Should the problem persist and the well water is still blue and it is discovered that the private well’s metal
discharge line has an electrical “grounding” clamp, have them contact a licensed electrician to investigate
the situation. The electrician would check the main circuit panel for a faulty, missing or improperly secured
“neutral” wire. He could also test the plumbing to see if there is any stray AC or DC current. There should
not be any current, even in milliamps! If there is current, the improperly functioning or shorted device/
appliance should be found and repaired. He should also check that the house plumbing has a greater resistance
(>25 ohms) than the grounding rod(s). The ground wire to the plumbing system should not be removed as it is mandated in the CT Building Code
but it should not be the primary carrier of stray electrical current or voltage surges to “ground” - CT DOH.[1]
Frequently Asked Questions (FAQs) About Copper Supply & Drain Piping in Buildings
Question: Acidic water & copper pipe corrosion/leak risk: Sage advice needed -- I have fairly acidic well water on Cape Cod – pH 6.3.
I get a lot of blue stains on bathtubs and sinks, which I assume is copper leached from the inside of the copper water-supply piping. I built the house about 16 years ago and replaced the water heater a few years ago.
Am I at risk of developing pin holes or other damage to the copper plumbing and other equipment, including an electric water heater, boiler, and baseboard radiation?
If that’s the case, what’s the preferred (and cheapest) solution: calcite neutralizer tank, soda ash feeder, or other?
FYI, copper level was last measured at 0.11 mg/L, well below the MCL of 1.3, so I don’t think there’s a health issue. But I figure if copper gets leached from the pipes for enough years, at some point there won’t be much pipe left.
Muchas gracias,
Steven Bliss,
4
Burlington, VT
Reply:
I do not have experience with pH treatment first hand, but it appears to me that the short answer is that for most situations, calcite filters are the easiest and cheapest method of treatment. But certainly experts have been looking at this problem for along time, and continue to research it. See Mattsson et als [14][15].
Before choosing one I'd measure the Langelier Saturation Index (LSI) of the water so you can figure out the level of treatment needed and check that against the treatment method proposed.
Incidentally, before water testing or asking your test company about what they commonly find in wells in your area of Cape Cod, don't rule out the water supply itself as contributing to the supply of dissolved copper. You could easily distinguish between copper from acidic effects on copper water piping and copper in the water supply by comparing two water tests, one taken from in the building (I give some aggressive testing suggestions below) and one taken from water where it enters the building, presumably through a plastic or galvanized iron well pipe (not a copper one).
Until you know the score, if there is a worry that pipes may already be thin or at risk, that's an extra reason to shut off water when leaving the property unattended. Some of the suggestions at WINTERIZE A BUILDING might help.
Acidic Water Treatments: Calcite Filters vs. Soda Ash Injection
According to the Clean Water Systems & Stores (who sell this equipment) , calcite neutralizer filters
... will typically raise the pH of the water to 7.0 to 8.0 and add 30 to 100 ppm of hardness depending on the alkalinity and water hardness. [2]
More sophisticated is a soda ash injection system. That approach requires a pump and metering device along with an intermediate tank to give the water enough contact time with the soda ash. And room to store 25 or 50 pound bags of soda ash. Like some other water treatment systems (like a chlorine injector) the soda ash injector pump is hooked up to run when the well pump turns on. It seems that a soda-ash injector system is recommended when the low pH of water is due to dissolved mineral acids (do you live near a mining site or in New York a natural gas from shale mining operation?).
On acidic well water and water corrosivity - Definition of the Langlelier Saturation Index
It's true that the lower the pH (more acidic) the higher the level of corrosivity of the water supply. But because pH is only one of several factors that will determine how corrosive the water is, while we should look at acidity or pH, if you want to know how worried to be about your water supply corroding your pipes, you want to perform a corrosivity test on your water.
But looking at building water supply properties and pipes and fixtures for evidence of what contaminants or water chemistry problems may be present can be confusing. Our faucet outlet (photo at left) shows both thick white mineral deposits (suggesting high calcium and high pH) and blue/green stains and deposits that might to some suggest acidic water and low pH.
While there is no doubt your water is
Definition of the Langelier Saturation Index - LSI & How it is Used
Experts us the Langelier Saturation Index (LSI) to estimate the corrosivity of a water supply. The Langelier Saturation Index or LIS is a number calculated from several factors and intended to tell you the chances that minerals, principally calcium are likely to precipitate out of the water.
Langelier, who developed this index, realized that the acidity or pH of water determines how much calcium carbonate CACO3 the water can hold. So a combination of the water's actual pH and the actual level of calcium in the water, along with other factors we list below, allow us to predict the chances that the water will leave scale in the plumbing system or components by precipitating out the calcium. We think of it as a more complete picture of water chemistry, with regards to both hardness (mineral content) and acidity or pH.
The Langelier calculation factors in the main components of corrosivity of a water supply including:
- Temperature of the water
- pH of the water
- total dissolved solids or TDS in mg/L
- Calcium level Ca in mg/L and whether or not the Ca is in the form of calcium carbonate CaCO3 or calcium ions Ca2+
- Alkalinity of the water (in mg/L as calcium carbonate)
these produce a Langelier Saturation Index.
Action Levels in the Langelier (LSI) Index
The Langelier index, when calculated ranges from +4 through 0 to -5. But you don't have to calculate anything. Just ask your water test company to perform this test for you, OR ask the water test company to test your water for hardness (you can do this free or cheap at MEASURE WATER HARDNESS ) and for corrosivity.
+4 LSI = scale producing water: At +4 the water is very likely to form scale deposits in the piping, especially hot water piping or in a water heater. Readers whose water is hard and/or has a high positive Langelier index should see WATER SOFTENERS & CONDITIONERS.
Zero LSI = just right: like the baby bear who found one of the porridges "just right", At an LSI of zero the water supply is "neutral" - it is not likely to precipitate calcium into the piping nor is it acidic enough to dissolve more calcium. With respect to the corrosive effects of acidic water on copper water piping, an LSI of zero also means the water is close to ideal - it is not corrosive to the piping.
At -5 LSI = corrosive water: at -5 LSI the water is extremely corrosive. Langelier index values of +0.5 to -0.5 are basically OK in that you wouldn't treat water at those levels.
If you decide to treat the water based on acidity alone or based on a Langelier index reading of -3 or lower (or optionally anywhere below -0.5) there are various systems that inject something basic like calcite (a calcite neutralizer tank or calcite neutralizer filter) or soda ash (a soda ash feeder) to treat the water and described above.
Other indices of water condition include the Ryznar Stability index that predicts water chemistry and how it will affect piping and appliances by examining the thickness of scale formation in municipal water systems, the Puckorius scaling index, the Larson-Skold index, the Stiff-Davis Index, and the Oddo-Tomson Index.[4]
Inspect your copper piping for evidence of leaks, corrosion, pinholes & leak risk factors
First, what quality of copper has been installed. Copper piping is sold in different weights or thicknesses. M is thin-walled, used in heating baseboards (you should be ok with that as the water in a hot water heating system does not keep changing out so corrosivity is normally limited); Types K (thickest) and L are used for water piping, M being the heavier grade, more resistant to corrosion perforation.
Therefore if your distribution piping is Type L you should inspect for corrosion on the pipe exterior - and beware that a small blue dot, when you scratch it, may become a rapid leak. Don't ever "pick" at corrosion unless you're prepared to shut down the water supply and clean up a leak. The bad news that has come up with some InspectAPedia readers, is that if you discover a length of copper piping with imminent or current pinholes, replacing just that section is not very comforting. Because the piping is corroding from the interior out, you won't see how thin and fragile other piping sections are ... until the next leak.
Also, corrosive water combined with waste and waste water risks corroding copper drain piping. Surprisingly you need to look along low-sloping runs of copper drain piping for evidence of corrosion or leaks along the top of the pipe, not just the bottom. It appears that droplets of highly corrosive condensate form along the upper surface of the pipes and remain in place for long periods, never being washed away by drain usage.
The World Health Organization, WHO, in discussing water pH, says
Exposure to extreme pH values results in irritation to the eyes, skin, and mucous membranes.
Eye irritation and exacerbation of skin disorders have been associated with pH values greater
than 11. In addition, solutions of pH 10–12.5 have been reported to cause hair fibres to swell
(10). In sensitive individuals, gastrointestinal irritation may also occur.
Exposure to low pH
values can also result in similar effects. Below pH 4, redness and irritation of the eyes have
been reported, the severity of which increases with decreasing pH. Below pH 2.5, damage to
the epithelium is irreversible and extensive (10). In addition, because pH can affect the degree
of corrosion of metals as well as disinfection efficiency, it may have an indirect effect on
health.
In addition, if well water at a particular building also happens to require disinfection, the pH is important and needs to be below 8.
What is the Optimum pH for a Building Water Supply?
WHO says in general the optimum pH target for drinking water should be 6.5 - 9.5, adding " No health-based guideline value is proposed for pH." [but they didn't appear to consider the effects of dissolved copper - if it occurs]
Other Causes of Pinhole Leaks in Copper Pipes in Buildings
Other causes of copper pipe pinholing or holing and leaks include
- scouring of the pipe interior by unusually high velocity water flow through the system.,
- sand, silt, or other abrasive contaminants in the water supply (you will probably detect these by clogged strainers at your faucets or clogged shower heads),
- improper electrical grounding of the electrical equipment or any other electrical appliances in the building
- and even a lightning strike.
We joined in investigating a site that had suffered what appeared to be a lightning strike - it was actually an electrical discharge from a high voltage power transmission line. A tree grew tall enough to contact the line, conducting power to the ground close to the home. Moisture under the garage floor slab vaporized, exploding the floor, sending the car up through the garage roof.
Electricity traveled across from the garage, apparently following tree roots, up an iron entry stair railing, over to aluminum siding (all the aluminum pop rivets melted and all of the the siding corner trim pieces fell to the ground), around the siding to a metal outdoor hose bib to metal water piping. Inside the building the water pipe was fused and melted, causing a basement flood.
Electrical Ground Wiring Errors Can Cause Plumbing Pipe Leaks
Watch out: also to check for electrical system connections that can significantly increase the risk of corrosion of the copper piping in the building. As you know, at most buildings the water piping system is grounded for safety, and sometimes a metal well pipe extending outside underground is used as a grounding electrode as well. Electricians recommend two driven grounding electrodes at modern properties (you can leave the old connection to a metal well pipe in place).
But interestingly, a mistake in the electrical panel, for example one that sends current improperly down the ground path, can speed up corrosion of building metal water pipes or other components.
I had a client in Pleasant Valley NY who twice replaced a very costly, supposedly corrosion proof nickel-plated co-axial ground-water-source heat pump temperature exchange coil. The purpose of the coil was to cool high temperature refrigerant gas back to a liquid state by cooling it using water pumped from a nearby well and for efficiency recycled through a holding tank for re-use before it was returned back to the ground from which it had originated.
When the heat pump stopped working I found that all of the refrigerant had leaked out of the system. But I couldn't find a leak in the refrigerant piping system. The only component I could not test directly with my halogen leak detector was the water-to-air heat exchanger coil itself. In an exciting discovery, I opened a drain to release water from the water-to-air heat pump system's water reservoir tank.
When I held my leak detector near the water stream, the detector went crazy, responding to a very high level of refrigerant gas that had become dissolved into the water.
We realized that the heat exchanger coil that was supposed to just cool the refrigerant gas was instead leaking that gas right into the cooling water supply.
Someone smarter than we were figured out where to look. The technician determined out that the heat exchanger coil was corroding and perforating because of improper electrical grounding within the heat pump.
Recommended Maximum Limits for Copper in Drinking Water
EPA's list of limits on contaminants in water (http://water.epa.gov/drink/contaminants/index.cfm#List)
is set in MCL (Maximum Contaminant Level), MCLG (Maximum Contaminant Level Goal) or mg/L (milligrams per liter) (mg/L === ppm) or parts per million - two ways of describing the same concentration
For copper EPA recommends both a MCLG and an "action level" of 1/3 mg/L for copper in drinking water, citing short term gastrointestinal distress (short term exposure) or liver or kidney damage (long term exposure). EPA also warns " People with Wilson's Disease should consult their personal doctor if the amount of copper in their water exceeds the action level"
Test the level of copper in your water - how to construct a "worst case" test
It would be instructive to test your water's copper content to see if it's unusually high. Not only would that tell us if acidic well water is corroding the pipe interior, you might find that the levels of copper are high enough to merit action for water safety / potability.
Making a "worst case" (most critical or "safest") measurement for copper or any other contaminant that might be found in drinking water due to dissolving the contaminant out of the water piping and supply system equipment can be done following the DF approach. We want to collect a sample of water that is most likely to represent the highest concentration likely to occur in household water that someone might drink.
To construct the "worst plausible case" scenario we collect a water sample after water has been sitting in the pipes for some time period. A longer wait period (days, weeks, months) might represent a house that has sat unoccupied for some time. But in my opinion I'd collect water that has sat overnight as a more likely and thus more plausible "worst case" scenario.
If all of the house plumbing is copper, you would, on "the morning after", go to a plumbing fixture most distant from the incoming water supply, pump, and tank, open a cold (test 1) water faucet and run enough water to flush out the faucet and any plastic fixture risers, so that we're sure we've got water that was in the copper piping overnight. Then collect the sample.
Watch out: at WATER TESTS, CONTAMINANTS, TREATMENT we discuss testing well water quality - what is "in" the well water that may make it unsafe or unpalatable to drink. Water that may be too high in mineral content, clogging pipes and water heaters (see MEASURE WATER HARDNESS), or water that is too acidic or corrosive, causing leaks in copper piping (see CORROSIVITY or ACIDITY of WATER). And at least as important is the question is "does the well provide enough water" - a topic discussed at How Much Water is In the Well? and at How to Test Well Water Quantity
Hot water and water pH - what happens to pH when we heat up the water?
You could collect a hot water sample as well, running water until it's hot, but because the "hot" water has arrived fresh from the water heater tank, it has not sat overnight in the piping and so is not such an aggressive test - I wouldn't bother. Not unless your home uses an antique copper water heater tank.
The WHO guidelines for drinking water quality points out some interesting technical detail,including that (at least for pure water) heating the water will decrease the water's pH. A pH decrease of 0.45 occurs when you raise water temperature by 25 deg. C. [13]
If the house has part plastic water supply piping, you'd want to see where the copper is located, calculate (by linear feet of pipe and its diameter) how much cold to run out to be sure you've collected a sample from inside the copper pipes.
That about exhausts me on copper pipes, pH, corrosion, copper testing, Langelier index, and treatment for low pH water. Thanks for asking.
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- [2] Clean Water Systems & Stores, Inc. 2806-A Soquel Ave, Santa Cruz, California 95062, Telephone: 1-888-600-5426 or international: 1-831-462-8500 . web search 4/23/12, original source: - cleanwaterstore.com/copper-pipe-corrosion.html
- [3] "pH in Drinking-water Background document for development of WHO Guidelines for Drinking-water Quality", in Guidelines for drinking-water quality, 2nd ed. Vol. 2. Health criteria and other supporting information, World Health Organization, Geneva, 1996. Web search 4/23/12, original source: http://www.who.int/water_sanitation_health/dwq/chemicals/en/ph.pdf
- [4] "Langelier Saturation Index (LSI), Wikipedia provided background information about some topics discussed at this website provided this citation is also found in the same article along with a " retrieved on" date. NOTE: because Wikipedia entries are fluid and can be amended in real time, we cite the retrieval date of Wikipedia citations and we do not assert that the information found there is necessarily authoritative.
- [5] "Drinking Water Contaminants, List of Contaminants & their MCLs", U.S. EPA United States Environmental Protection Agency, National Primary Drinking Water Regulations, web search 4/23/12, original source: http://water.epa.gov/drink/contaminants/index.cfm#List
- [6] "Basic Information about Copper in Drinking Water", U.S. EPA United States Environmental Protection Agency, web search 4/23/12, original source: http://water.epa.gov/drink/contaminants/basicinformation/copper.cfm
- [7] "Fin Tube / Bare Elements", Slant/Fin Boilers & Baseboards, Slant/Fin Corporation, 100 Forest Drive, Greenvale, NY 11548, Phone: (516) 484-2600, Fax: (516) 484-5921, E-mail: info@slantfin.com, web search 4/23/12, original source: http://www.slantfin.com/index.php/products/baseboard-residential/fin-tube--bare-elements
- [8] Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com 11/06
- [9] Roger Hankey is principal of Hankey and Brown home inspectors, Eden Prairie, MN. Mr. Hankey is a past chairman of the ASHI Standards Committee. Mr. Hankey has served in other ASHI professional and leadership roles. Contact Roger Hankey at: 952 829-0044 - rhankey@hankeyandbrown.com. Mr. Hankey is a frequent contributor to InspectAPedia.com.
- [10] Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
- ABS Plastic Drain/Waste/Vent (DWV) pipe failures: reported for Centaur, Phoenix, Polaris, Gable, and Spartan pipe mfgs. for pipe made between 1985 and 1988. CPSC Hot Line: 800-638-8270 or ABS Drain Leaks/Failures-Class Action Settlement COX settlement through Shell Oil set up by a contractor involved in the settlement. Polybutylene Plumbing Failures: Spencer Class settlement. 10% of replacement cost/damages, only for acetal (plastic)fittings Polybutylene plumbing info at U. Arizona Polybutylene piping lawsuit settlement website Polybutylene plumbing lawsuit proposed settlement-old site
- [11] Polybutylene Plumbing Failures, Lots of Info about, but slow-loading busy site
- [12] Compression fittings for plumbing connections, Wikipedia photograph, web search 08/09/2010, original source: http://en.wikipedia.org/wiki/File:Robinetterie-raccords.JPG
- [13] "Guidelines for drinking-water quality", 2nd ed. Vol. 2. Health criteria and
other supporting information. World Health Organization, Geneva, 1996.
WHO, op.cit.
- [14] "Pitting Corrosion in Copper Tubes – Cause of Corrosion and Counter-Measures", Mattsson, E.; Fredriksson, A.-M., British Corrosion Journal, Volume 3, Number 5, September 1968 , pp. 246-257(12), Maney Publishing, Quoting the article abstract:
An investigation of failures of hard-drawn copper water pipes (phosphorus-deoxidised copper) in service due to pitting corrosion was conducted from November, 1962 to February, 1965. Fifteen cases were reported. All those about which information could be obtained came from hot water installations and occurred in water with a low pH (?7) and a HCO3- content of, at the most, 100 mg/l but generally below 50 mg/1. Failures not due to pitting corrosion (i.e. caused by erosion and corrosion or corrosion fatigue) occurred in waters with a higher pH and higher HCO3- content.
A laboratory investigation into the ability of the corrosion products to counteract further corrosion in different types of water was also carried out, using an electrolytic cell which, in principle, was a model of an active pit in a copper tube. This led to the following conclusions, which are in good agreement with the results obtained from the examination of service failures:
If the pH value of the water is high enough, the copper dissolved by the corrosion can be precipitated as basic copper salt. At low pH values such precipitation does not take place.
If the [HCO3?]/[SO42?] ratio in the water is high, dissolved copper can be precipitated as basic copper carbonate in the neighbourhood of the corrosion site and counteract further corrosion.
At a low [HCO3?]/[SO42?] ratio, crusts of basic copper sulphate will be precipitated at some distance from the corrosion site and may lead to a high corrosion rate.
Pitting is not likely to occur in hot water tubes of hard copper if the pH is ? 7·4 and the [HCO3?]/[SO42?] ratio ?1 (the concentrations given in mg/1). The critical values mentioned are approximate and may be adjusted in the light of future experience.
- [15] "Health and aesthetic impacts of copper corrosion on drinking water",
Dietrich AM, Glindemann D, Pizarro F, Gidi V, Olivares M, Araya M, Camper A, Duncan S, Dwyer S, Whelton AJ, Younos T, Subramanian S, Burlingame GA, Khiari D, Edwards M., Virginia Tech, Blacksburg, VA 24061-0246, USA. andread@vt.edu, Water Sci Technol. 2004;49(2):55-62., Abstract
Traditional research has focused on the visible effects of corrosion--failures, leaks, and financial debits--and often overlooked the more hidden health and aesthetic aspects. Clearly, corrosion of copper pipe can lead to levels of copper in the drinking water that exceed health guidelines and cause bitter or metallic tasting water. Because water will continue to be conveyed to consumers worldwide through metal pipes, the water industry has to consider both the effects of water quality on corrosion and the effects of corrosion on water quality. Integrating four key factors--chemical/biological causes, economics, health and aesthetics--is critical for managing the distribution system to produce safe water that consumers will use with confidence. As technological developments improve copper pipes to minimize scaling and corrosion, it is essential to consider the health and aesthetic effects on an equal plane with chemical/biological causes and economics to produce water that is acceptable for public consumption.
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