Information and Sources on Certain Plumbing Issues
Note: This information was copied and pasted here from various internet sites.
No one expects a well-designed and manufactured product to fail to function as soon as it is taken out of the box. Equally it is unrealistic to expect the same product to last forever! A realistic expectation is that it will give useful service for a period of time that offsets the cost of replacement and when it fails this will be in a benign manner that does not affect safety or the environment. When this "lifetime" issue is primarily a result of mechanical performance most design and maintenance engineers, and product manufacturers, are well armed with tools, procedures and qualified personnel. It is also very likely that products are redesigned often to optimize their performance, minimize cost and take advantage of developments in technology and understanding. Unfortunately, this situation is not true for all the factors that affect the lifetime; corrosion and its control is rarely given enough resources or regular attention yet it is a common cause of failure. When was the last time that your organization reviewed its capability in this area and the effect that a problem would have on your customers and your business? http://www.npl.co.uk/lmm/audit/
Brass is defined as a copper alloy that contains 5 to 40 percent zinc as the principal alloying element (among other metals, including tin, iron, aluminum, nickel, silicon, and lead). Zinc is added to brass to increase tensile (tension) strength. Lead is added to brass to improve “machineability” and to make castings pressure tight by filling the voids created as the casting cools. Brass to make household fixtures used to contain 1.5 to 7.5 percent lead.
Solder is a metallic compound used to seal plumbing joints. Most solder used to contain about 50 percent lead. The 1986 amendments to the Safe Drinking Water Act banned the use of solders containing more than 0.2 percent lead in public water systems and household plumbing. The use of lead in pipes and brass fixtures was restricted to 8 percent or less under the Safe Drinking Water Act Amendments of 1996. Despite this regulation, lead containing solder may still exist in many aging distribution systems and household pipes.
Homes that have lead solder, or homes that are connected to the water main by a lead service line, are more likely to have higher levels of lead in their water than those that do not. Experts regard this lead-containing solder as one of the major causes of lead contamination of household drinking water in U.S. homes.
Brass fixtures and solder act as sources of dissolution corrosion. Brass fixtures (including faucets) act as sources for dezincification corrosion. Dissolution refers to the dissolving of the metals (that make up the alloy) into the solution in contact with the metal. In this way, metals such as lead, copper, chromium, and cadmium can leach from brass fittings into our drinking water.
Dezincification is a specific type of de-alloying, or selective, leaching corrosion. This type of corrosion selectively removes zinc from the alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. This weakens the integrity of the pipes and can form blockages. http://www.epa.gov/ORD/NRMRL/wswrd/cr/corr_res_brass.html
De-alloying corrosion, known as ”Dezincification,“ was effectively eradicated from valve products in the 1950s.
Today, however, this problem has returned with the increased use of high-zinc alloys (commonly referred to as ‘Yellow Brass’) in forged and cast valves typically produced outside the United States.
Dezincification selectively removes zinc from the alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. The physical attributes of an in-service valve with Dezincification includes a white powdery substance or mineral stains on its exterior surface.
What’s the cure? On all bronze valves the metal components in the waterway must not contain more than 15% zinc in their chemical makeup.
As a standard NIBCO bronze irrigation valves are made to be “Dezincification Resistant,” which is a seal of quality and longevity. http://www.nibco.com/assets/bronzebvfigkey.pdf
These alloys contain zinc as the principal alloying element with or without other designated alloying elements such as iron, aluminum, nickel and silicon. The wrought alloys comprise three main families of brasses. The cast alloys comprise five main families of brasses. Ingot for remelting for the manufacture of castings may vary slightly from the ranges shown.
In these alloys, zinc is added to copper in amounts ranging from about 5 to 45%. As a general rule, corrosion resistance decreases as zinc content increases. It is customary to distinguish between those alloys containing less than 15% zinc (better corrosion resistance), and those with higher amounts. The main problems with the higher zinc alloys are dezincification and stress corrosion cracking (SCC). In dezincification, a porous layer of zinc free material is formed locally or in layers on the surface. Dezincification in the high-zinc alloys can occur in a wide variety of acid, neutral and alkaline media.
Dezincification can be avoided by maintaining the zinc content below about 15%, and minimized by adding 1% tin such as in Admiralty brass (C44300) and Naval brass (C46400). Adding less than 0.1% of arsenic, antimony or phosphorus gives further protection, provided the brass has the single a-phase structure. Again, a decrease in the zinc content to less than 15% is beneficial. Brasses containing less than 15% zinc can be used to handle many acid, alkaline and salt solutions, provided:
http://www.corrosionsource.com/technicallibrary/corrdoctors/Modules/MatSelect/corrbrass.htm
and also at http://www.corrosion-doctors.org/MatSelect/corrbrass.htm
Dezincification selectively removes zinc from the alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. An in-service valve suffering from dezincification has a white powdery substance or mineral stains on its exterior surface. The valve may exhibit water weeping from the valve body or stem/bonnet seal.
What's the cure? A tightly written valve specification that limits brass alloys to those containing no more than 15% zinc, or specification of proven dezincification-resistant yellow brass alloys, say the experts. Further, manufacturers must be required to provide alloy designations or chemistry for the materials used in their valves and fittings. Over the past decade, an evolution in alloys has occurred, and yellow brasses that are dezincification-resistant do exist. However, specifiers who simply accept inexpensive yellow brasses without regard to whether they are standard alloys-or even meet the performance requirements of standard alloys-are vulnerable to potential dezincification problems.
Why Dezincification Occurs Copper-zinc alloys containing more than 15% zinc are susceptible to dezincification. Zinc is a highly reactive metal, as seen in its galvanic series ranking. This reactivity stems from the fact that zinc has a very weak atomic bond relative to other metals. Simply, zinc atoms are easily given up to solutions with certain aggressive characteristics. During dezincification, the more active zinc is selectively removed from the brass, leaving behind a weak deposit of the porous, more noble copper-rich metal.
Conditions favoring dezincification are contact with slightly acid or alkaline water. Not highly aerated, low rates of flow of the circulating liquid, relatively high tube-wall temperatures and permeable deposits or coatings over the tube surface.
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Two types of corrosive attack characterize dezincification:
http://www.corrosion-doctors.org/Forms/dezinc.htm
Dezincification is an example of "dealloying" in which one of the constituents of an alloy is preferentially removed by corrosion. Another example is graphitisation of cast iron. Cast iron has a structure comprising essentially two components - graphite and ferrite. Corrosion causes progressive dissolution of the ferrite (iron) constituent leaving the graphite behind. The dezincification of brass is a little more complicated since the zinc and copper are not present as separate constituents but as alpha and beta solid solutions. The effect of dezincification corrosion is however similar to graphitisation in that one constituent of the alloy (zinc) is selectively removed leaving the other (copper) behind. The mechanism by which this occurs is probably different in that, instead of the zinc being selectively leached out from the brass, the zinc and copper both pass into solution together but the copper is then almost immediately redeposited in virtually the same position that it occupied originally. The result therefore is to remove the zinc as corrosion products and leave a residue of copper. Dezincified brass, like graphitised cast iron, retains the original shape and dimensions of the metal component before corrosion but in both cases, the residue is porous and has very little strength.
Dezincification was first recognised as a serious problem in 70/30 brass tubes used for ships’ condensers before about 1920. It was stated that "Condenseritis" i.e. Dezincification of condenser tubes had more effect than the Germany navy in putting HM ships out of action in the first world war. Research on the problem by G D Bengough and R May () established that dezincification could be prevented by the incorporation of about 0.03% arsenic in the 70/30 brass alloy and this addition is now standard in all alpha-brass tube specifications including admiralty brass and aluminium brass. Alpha-brass strip is not usually arsenical since it is mostly used in situations where dezincification does not occur or is not significant.
Dezincification as a problem with alpha-beta brass water fittings in some districts was first recognised in the late 1950’s. This was a type of dezincification, now termed "meringue dezincification", in which the zinc passing into solution from the brass forms very bulky hollow mounds of corrosion product which block the fitting. It attacks the beta phase preferentially but spreads at a later stage into the adjoining alpha phase. This is illustrated in the photo-micrograph, figure 1, in which the alpha and beta phase have both suffered dezincification near the surface of the metal but in the interior the attach is clearly restricted to the beta phase. Since the addition of arsenic to the alloy does not inhibit dezincification of the beta phase, arsenic additions are of no value in alpha-beta brasses.
Dezincification may show itself as dull red spots developing on the surface of brass after long periods of exposure to urban or industrial atmospheres. These do not normally represent any significant loss of strength in the component concerned but, since they are more than simply superficial they cannot be removed by the cleaning and polishing procedures that would normally restore the brass to its original appearance.
Dezincification in water fittings, valves etc. can show itself in a variety of ways depending on the water composition and service conditions. Blockage due to meringue dezincification has already been mentioned. Other possible manifestations are seepage of water through the walls of fittings after long periods of service or leakage at valve seatings due to dezincification coupled with erosion of the soft, dezincified residue. The extreme case of damage by dezincification is actual breakage, with a dull coppery appearance to the fracture surface. Breakage is not common but can affect alpha-beta brass underground fittings (in which dezincification may be occurring from both the water side and the soil side) valve spindles, screws and "bronze-welded" joints.
The possibility of spots of dezincification occurring as a result of long exposure to polluted atmospheres has already been mentioned. Service conditions that can give rise to more significant dezincification usually involve acidic or highly saline conditions. These include for example exposure to waters with a pH below 7. Such waters are not normally used for public supplies in the UK but some private supplies, mine waters and industrial rinse waters are sufficiently acidic to cause dezincification in susceptible brasses. Service in sea water or brackish water is also likely to produce dezincification in susceptible brasses as is burial in corrosive soils such as acid peat, salt marsh, waterlogged clay, or made-up ground containing cinders.
The particular form of dezincification giving rise to bulky corrosion products (meringue dezincification) is associated with waters having a high chloride to temporary hardness ratio, coupled with a high pH usually above 8.0 and often above 8.3 water compositions falling within the shaded area in figure 13 are liable to cause meringue dezincification of alpha-beta brass fittings. The boundary between the shaded and clear area is not precise and any water composition close to the boundary should be regarded as potentially liable to cause meringue dezincification. It should also be noted that waters with a composition just within the shaded zone can cause as rapid dezincification as waters with compositions well within it.
The water supplies to most parts of the UK, including almost all the major centres of population, are of compositions that do not give rise to meringue dezincification. The waters that do give trouble are certain moorland-derived supplies (but by no means all such waters) and lowland river supplies that have been treated by the lime-softening process. Water authorities in areas where water liable to cause meringue dezincification is supplied usually advise the use of dezincification resistant materials for water fittings. This advice does not however generally apply to terminal taps since the flow conditions in these are such that the hollow shells of meringue corrosion product do not build up.
Two factors that can increase the probability and rate of dezincification occurring in service are elevated temperature and coupling to a more noble metal. If brass bosses are used on copper hot water cylinders the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally give no trouble at all. Consequently this is one point in a domestic plumbing system where brasses are not used; the British standards covering the construction of copper water cylinders specifically require the bosses to be of dezincification-resistant materials.
Dezincification problems in service can be avoided by recognizing in advance whether the service conditions are likely to produce dezincification and, if so, using appropriate dezincification-resistant brasses. For heat-exchanger or other tubing the question solves itself since all alpha brass tube specifications require the presence of arsenic in the alloy to inhibit dezincification. Alpha brass strip or sheet, other than aluminum brass, is not usually arsenical since it is mostly used for purposes where no significant dezincification will occur. For more corrosive conditions aluminium brass strip can be used, or one of the higher-copper brasses, with 15% or less of zinc, which are practically immune to dezincification. Nickel silvers also show high resistance to dezincification and can be an appropriate choice for some applications when this property is important.
If the manufacturing process involves hot stamping or requires free machining rod or bar, alpha beta brasses are normally used but these are susceptible to dezincification in unfavourable environments.
Research work solved this problem by producing brasses which, at the hot stamping or extrusion temperature, contain sufficient beta phase to be hot-worked satisfactorily but which can be converted by subsequent heat treatment to an all-alpha structure which is protected against dezincification by incorporating arsenic in the alloy. Such a forgeable, dezincification resistant brass has, since 1980, been included in BS2872, "copper and copper alloys, forging stock and forgings" and BS2874 "copper and copper alloys, rods and sections (other than forging stock)" under the designation "CZ132". CZ132 is a leaded brass and its machinability is comparable with the leaded duplex brass, CZ122, commonly used for production of water fittings. CZ132 rods and bars for machining are heat treated by the materials supplier to put them into the dezincification-resistant condition. CZ132 forging stock is supplied unheat-treated since it must be heat treated in the range 450-550oC after forging to ensure resistance to dezincification. This is done by the fittings manufacturer.
To retain corrosion resistance, fittings should not be reheated above the heat treatment temperature, as happens in brazing. If accidentally overheated, corrosion resistance can be regained by repeating the original treatment.
BS2872 and BS2874 specify a test for resistance of samples of CZ132 brass to dezincification. This involves exposure to a 1% solution of cupric chloride at 75oC for 24 hours followed by examination of sections to establish the maximum depth of any dezincification that has occurred. The sample passes the test if the maximum depth of dezincification in a forging or in the transverse direction of extruded material does not exceed 100m m. A maximum depth of 200m m is permitted in the longitudinal direction of extruded material. The European Standard version of this test is referenced in BS EN ISO 6509 and the maximum permitted depths of dezincification are defined in product standards.
This test and these criteria for acceptance are also applied by the Water Fittings Approvals Board to fittings made from brasses other than CZ132 which the manufacturers claim to be resistant to dezincification. Water fittings accepted by the approvals boards are listed in the board’s publication "Water Fittings". Those described therein as being of dezincification-resistant brass have been subjected to the cupric chloride test specified for CZ132 and have performed satisfactorily. They are identified by the mark ‘CR’ embossed or engraved on the side of the fitting.
It should be noted that there are some proprietary brasses that are described as "dezincification-resistant" by the manufacturers, and would be accepted as such in Scandinavia where a maximum depth of dezincification of 400m m in the cupric chloride test is permitted, but which cannot meet the 100m m maximum depth of attack which would make them acceptable as dezincification-resistant fittings in UK. Such fittings are not listed as dezincification-resistant by the approvals board and do not carry the ‘CR’ mark.
Two types of brass are in common use. The higher copper brasses generally contain over 63% copper and have a single-phase (alpha) structure. These are used particularly for their good cold forming properties as in deep drawing or in tube drawing. For optimum hot working properties, required for manufacture of water fittings by hot stamping, brasses of a lower copper content with a duplex (alpha-beta) structure are used.
Dezincification was first recognized as a serious problem in the alpha brass used for ships condenser tubes but alloying additions were developed which made the material immune. The same additions do not succeed with the duplex brasses because of the presence of beta phase as well as the alpha.
Dezincification first became a recognized problem with duplex brass water fittings in the late 1950’s, when certain water authorities banned the use of duplex brass fittings, after experiencing rapid blockage of hot water fittings as a result of dezincification. Research carried out by the British Non-Ferrous Metals Research Association (BNFMRA, later the BNF Metals Technology Centre) in collaboration with the Copper Development Association and the British Waterworks Association (now the National Water Council) established the relationship between the composition of supply waters and their liability to produce dezincification. The number of areas affected was not large and the problem was overcome by manufacturers developing ranges of fittings in copper or gunmetal which are immune to dezincification and could be specified for use in the areas concerned.
Later developments in the water supply industry, involving new large-scale schemes for water abstraction and treatment and facilities for interchange of water between different supply areas, revived concern about the risk of dezincification in water fittings. In 1969 the brass industry, together with BNF, set up a further programme of research aimed at developing a brass suitable for manufacture of water fittings by hot stamping but resistant to dezincification. Over the next five years this research established the range of alloying additions and the heat treatment that would provide a brass which, at the hot stamping temperature, would contain sufficient beta phase to forge satisfactorily but could by subsequent heat treatment, be converted to an all-alpha structure protected against dezincification. The laboratory work was followed by practical evaluation of the material in a wide range of waters and is described in a paper by J E Bowers and colleagues (). Their work culminated in 1980 in the publication of amendments to BS 2872 and 2874 defining the composition, mechanical properties, heat treatment and dezincification testing criteria for forgings and extruded bar in CZ132.
The results of standard tests of the acceptability of these fittings show them to be completely safe for handling potable water.
Many manufacturers now make fittings of dezincification-resistant brass CZ132 and most popular types and sizes of fittings are available from stock. High standards of quality control are required to ensure that the composition and heat treatment are correct and it has been agreed between the National Water Council (NWC), National Brass Founders Association (NBA) and the Copper Tube and Fittings Manufacturers Association (CTFMA) that fittings in dezincification resistant brass made to these standards should carry the ‘CR’ identification mark.
Although CZ132 was developed primarily for resistance to meringue dezincification in domestic plumbing systems its use is not restricted to fresh water service. Following a one-year test of a submerged sea water filter, in which suspension lugs machined from CZ132 bar showed no dezincification, while a naval brass plate containing less than 10% beta was dezincified to a depth of 150m m (), CZ132 has been accepted by Lloyd’s Register of Shipping, Yacht and Small Craft Department for through-hull fittings in sea water service.
http://www.hghouston.com/coppers/brass75.htm
Rain hits the ground as a weak acid H2CO3 (Carbonic Acid). If it runs across calcium and/or magnesium in the ground on the way to a well or reservoir it dissolves some of it. These two minerals raise the ph (acid) condition of the water up to neutral but they constitute the hardness found in water. Hardness is not considered a health threat and therefore it is not treated in public water supplies. Public water is just as likely to be hard as well water. Hard water will shorten the life and ruin the efficiency of any kind of Water Heater. It will also significantly shorten the life and ruin the appearance of all faucets and plumbing fixtures. Hard water uses up soap products at a rate 3 to 4 times greater than soft water. It leaves the film on fixtures, tubs and showers that is so hard to clean. Soft water allows you to eliminate the use of many cleaning products the thing you still use will work just as well or better with 1/3 or 1/4 as much as you are presently using. It is not unusual for a family of four to save the cost of the water softener in just a few years on cleaning products they buy at the grocery store. http://www.wefixwater.com/WhatIsGoodWater.htm
I'm sure you've heard the terms 'hard water' and 'soft water', but do you know what they mean? Is one type of water somehow better than the other? What type of water do you have? Let's take a look at the definitions of these terms and how they relate to water in everyday life.
Hard water is any water containing an appreciable quantity of dissolved minerals. Soft water is treated water in which the only cation (positively charged ion) is sodium. The minerals in water give it a characteristic taste. Some natural mineral waters are highly sought for their flavor and the health benefits they may confer. Soft water, on the other hand, may taste salty and may not be suitable for drinking.
If soft water tastes bad, then why might you use a water softener? The answer is that extremely hard water may shorten the life of plumbing and lessen the effectiveness of certain cleaning agents.
When hard water is heated, the carbonates precipitate out of solution, forming scale in pipes and tea kettles. In addition to narrowing and potentially clogging the pipes, scale prevents efficient heat transfer, so a water heater with scale will have to use a lot of energy to give you hot water. Soap is less effective in hard water because its reacts to form the calcium or magnesium salt of the organic acid of the soap. These salts are insoluble and form grayish soap scum, but no cleansing lather. Detergents, on the other hand, lather in both hard and soft water. Calcium and magnesium salts of the detergent's organic acids form, but these salts are soluble in water.
Hard water can be softened (have its minerals removed) by treating it with lime or by passing it over an ion exchange resin. The ion exchange resins are complex sodium salts. Water flows over the resin surface, dissolving the sodium. The calcium, magnesium, and other cations precipitate onto the resin surface. Sodium goes into the water, but the other cations stay with the resin. Very hard water will end up tasting saltier than water that had fewer dissolved minerals.
Most of the ions have been removed in soft water, but sodium and various anions (negatively charged ions) still remain. Water can be deionized by using a resin that replaces cations with hydrogen and anions with hydroxide. With this type of resin, the cations stick to the resin and the hydrogen and hydroxide that are released combine to form pure water.
http://chemistry.about.com/cs/howthingswork/a/aa082403a.htm
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