Engineering the Basics

Part 17(b)—Mechanical Design, Piping, Part 2

By Ed Butts, PE, CPI

In the last edition of The Water Works, we introduced the piping used in water system applications and the various design considerations of strength, including external and internal pressure, thrust restraint, and water hammer and surge pressures.

In this installment, we will conclude this discussion with an overview on fluid parameters as well as the potential for corrosion or encrustation, the different types of coatings and linings used in water works piping, and a brief review of designer and client preference in piping.

Potential for Corrosion and Encrustation

The properties of conveyance and surrounding fluids on both interior and exterior pipe surfaces can generally cause one of two potential actions upon the pipe material: corrosion or encrustation.

Corrosion is an electrochemical attack on the pipe material, which is generally metallic, that results in a methodical loss of material at one site only to be usually transported and redeposited to another adjacent site.

Encrustation, on the other hand, is primarily an electrochemical reduction-oxidation (redox) reaction or precipitation process, where specific dissolved elements or compounds revert to a settleable solid that deposits or adheres onto the pipe’s surface, a process referred to as scaling.

Technically, corrosion can occur with any material, even though it is most often associated with metals. Encrustation, meanwhile, can and does occur with and to virtually any pipe material or combination of materials.

Generally, few water systems or pipelines catastrophically or suddenly fail as a direct cause from one of these conditions since various warning signals usually predate these events. However, either condition can greatly contribute toward an ultimate failure.

For example, encrustation can cause a gradual but progressive decline in water system production over time due to the deposition of mineral scaling onto interior pipe walls. Corrosion slowly dissolves or removes exposed or submerged metallic material, eventually causing voids to occur in metallic piping which in turn can lead to a total pipeline or system failure if not addressed and remedied in time.

Virtually all water systems are influenced in one way or another by the electrochemical processes that lead to corrosion and encrustation. Thus both potentials must be adequately examined during the design phase to avoid an undesirable result in service.

Corrosion can occur in many different forms such as stress corrosion, graphitization (cast-iron corrosion), dezincification (loss of zinc), and crack corrosion. As far as water system components are concerned, though, the most common corrosion is classified as either electrochemical (also known as galvanic) or chemical in nature.

Chemical corrosion occurs when a specific condition, compound, or element is present in the water in adequate concentrations to result in a progressive removal of the pipe wall material. Examples of water or environmental conditions include higher water temperature or increasing fluid velocity. Impacting compounds and elements include carbon dioxide, dissolved oxygen, hydrogen sulfide, and chlorides, in addition to many acids.

Generally, chemical corrosion causes a total loss of the metal, with the loss of metal completely dissolved and transported away from the site of the parent material. Electrochemical corrosion causes a loss of material along a portion of a pipe followed by a redeposition of these corrosion products onto other adjacent sections of the same assembly of pipe.

Chemical corrosion usually occurs in waters with both low pH and total dissolved solids. Electrochemical corrosion, on the other hand, occurs in waters with both higher pH values and levels of total dissolved solids. These higher values are necessary for the water to act as the electrolyte needed to transmit an electrical current.

Additional factors needed to determine if chemical corrosion is possible are high levels of dissolved oxygen, carbon dioxide (which is usually accompanied by a low pH), and temperatures. These factors alone, or combined, can accelerate chemical corrosion to the extent the pipe will often last for a period of only two to three months.

Corrosion is influenced by several parameters: chiefly the fluid’s pH, conductivity, chemical balance, alkalinity, and temperature.

Encrustation can occur as the result of two types of chemical reactions: precipitation or electron transfer (redox potential). Both reactions can and often do occur simultaneously and at the same location.

Precipitation is caused by one or a combination of reactions due to water temperature, pressure changes, and the concentration of the salts present in the water. The most commonly found salt in water wells is the compound that causes water hardness (calcium carbonate, CaCO3), although other compounds can also cause precipitation, such as ferrous hydroxide (dissolved iron in solution), ferric hydroxide (reduced iron), and manganese hydroxide (dissolved manganese).

Protection Against Corrosion and Encrustation

Potential corrosion to a pipeline is generally diminished through one of two methods: (1) using a material with reasonably inert corrosive properties, such as most thermoplastics; and (2) providing a barrier between the pipe surface and the transported fluid.

Most thermoplastics (such as PVC and HDPE) are reasonably neutral to most corrosive attack since the material does not inherently possess the necessary electrical conductance needed for electron transfer. Thermoplastics usually offer excellent corrosion resistance, except for the presence of solvents.

Barriers use an insulating layer that physically separates the pipe material from the fluid or electrolyte. This type of protection is generally afforded on interior metallic surfaces, such as steel and ductile iron, in the form of a cement or epoxy lining. However, the barrier method is not as effective as using inert materials since there will always be small cracks and fissures in the barrier coating that will allow direct attack
between the fluid and the exposed pipe material.

In many cases, these damages of the barrier can result in a worsening and accelerated attack to the pipe due to the concentrated amount of exposed material as opposed to the more progressive attack observed when a greater overall surface area is exposed.

Pipe Coatings and Linings

Using an appropriate coating or lining between the electrolyte, usually water, and the piping material can provide an effective physical barrier to resist corrosive or scaling actions and extend the service life of the material.

Obvious material types where this may be an advantageous addition include carbon steel, cast iron, and ductile iron. The use of an interior lining or coating, when exposed to potable water, must comply with specific water quality standards.

The most recognized, NSF/ANSI 61 is an established health effects standard adopted by most states. It evaluates the level of contaminants that could leach from the pipe or coating products into drinking water.

NSF/ANSI 61 requires a toxicological evaluation of chemical concentrations to ensure they are below levels that may cause potentially adverse human health effects. The toxicological evaluation criteria are based on an equivalent lifetime exposure to the concentration of contaminants in drinking water.

NSF Standard SE 9857 is a specification for specially engineered products and a requirement for internal epoxy pipe coatings produced specifically for use on the interior of metallic potable water pipe—applied using a mechanical means. The specification establishes the minimum testing, marking, and in-plant quality control requirements for epoxy coatings to be used on the internal surfaces of potable water pipe.

Specifications written to protect owner assets often include requirements of material conformance to American Water Works Association standards for coating systems to be used on the interior of water transmission pipe. Currently, there are 23 approved standards under the auspices of AWWA’s steel pipe committee. Of these standards, 14 deal with coatings and linings that are available for the protection of metallic pipe and five are applicable to linings of all water transmission pipe. The distinct AWWA testing standards for each type of lining are shown in Table 1.

All AWWA pipe coating standards are based on the maximum service temperature of potable water. The purpose of the standards is to provide the minimum requirements for coating systems used for the interior coating of steel water pipelines including material, application, inspection, testing, handling, and packaging requirements.

The applied and finished thickness of a coating is vested in a mil, or one-thousandth (1⁄1000) of an inch. The thickness of each type of coating varies with the type of coating, pipe material, service and application conditions, and number of coats required to achieve a final coating.

Many multi-layer coatings are applied at 3-5 mils per application, with a finished film thickness of 10-20 mils common for many coatings.

There are five common types of interior coating or lining material used for steel potable water transmission pipe. The table includes coal tar enamel, cement mortar, liquid-applied epoxy, fusion bonded epoxy, and polyurethane. Each of these lining technologies have inherent advantages and limitations. Additionally, each interior coating type has installation requirements for surface preparation and application.

Coal Tar Enamel

Coal tar pitch, which forms the basis for coal tar enamel (CTE), consists of stable molecules formed during coking operations at temperatures of around 1300°C (2372°F). The fillers and coal add flexibility and strength to the product. This strong molecular arrangement provides CTE with the characteristics necessary to produce pipeline corrosion protection. These characteristics can be summarized as follows:

  • Water resistant: Negligible water absorption and vapor transmission.
  • Stable chemical structure: Resistant to acid and alkali substances.
  • Resistant to a cathodic loss of bond: Many underground pipelines are protected using impressed current or sacrificial
    metal anodes; CTE is resistant to the alkaline environment formed at exposed metal surfaces.
  • High electrical resistance: Even after a long period of water immersion, the electrical resistivity remains high.
  • Adhesion: Forms a strong permanent bond to the metal surface.
  • Generally resistant to attack by bacteria, marine organisms, and root penetration.

Shortages in the availability of qualified applicators, increasing costs, possible issues of worker exposure during application, concerns regarding the potential leachability of trace contaminants into the potable water, and possible negative effects on human health have universally contributed to the decline in the use of coal tar enamel—especially in the United States. In fact, in many locales, coal tar enamel is no longer permitted for use with potable water.

Surface preparation is critical to proper CTE performance and application of CTE requires an understanding of its limitations during cold weather and high humidity. Coal tar enamels generally require heating and continuous agitation of the material during application and the enamel is required to be maintained free of moisture and dirt during the application process.

Cement Mortar

Cement-mortar linings provide long-term protection at a relatively low cost and remain one of the standard linings in use for potable water pipes, particularly ductile iron pipe.

A major benefit with cement mortar is the ease of application since the mixing and application of mortar is straightforward, leading to relatively low risks during application.

Cement-mortar linings provide active protection of the underlying pipe by creating a stable hydroxide film at the pipe-mortar interface. The corrosion protection is referred to as active because it provides protection even where there are discontinuities in the lining.

Cement-mortar linings have an excellent and long track record of conveying water for extended periods to required water quality standards and currently meet all applicable standards throughout the world as they do not support microbiological growth.

The actual cement application of cement-mortar linings is performed by pumping or pouring a high slump value of cement mixture onto a slowly rotating length of pipe. The rotating speed is then increased, creating centrifugal forces that level out the wet mortar to a uniform thickness. Continued spinning removes the excess water and compacts the mixture to a dense and solid surface.

After the spinning process, the lining is cured either by exposure to moist air at ambient temperature or by an accelerated process using steam.

As with a concrete mix, cement-mortar linings can develop drying cracks, but these cracks will self-heal when the lining is wet. Wetting the cement lining also causes the lining to swell, which increases strength and improves adherence.

Cement-mortar linings can also add significant stiffness for resistance to deflection forces. The strength of the mortar lining lining may be added to the strength of the pipe when calculating stiffness.

Soft and aggressive waters, as well as prolonged contact with heavily chlorinated water, may well be detrimental to cement-mortar linings.

Cement-mortar linings perform best when the flow velocity in the pipe is 20 feet per second or less. In situations where the conveyed water is aggressive and the flow rate or velocity is low, resulting in a long residence or contact time, a high pH can develop with cement-mortar-lined pipe due to leaching of the alkali from the cement component.

Cement-mortar linings add considerable weight to the section and reduce the available flow volume of a transmission pipe when used with international pipe sizes. However, ductile iron pipe is generally larger than the nominal pipe diameter, increasing the conveyance area by up to 10% over nominal pipe sizes.

Liquid-Applied Epoxy

The liquid-applied epoxy lining systems may consist of any of the following three types:

  • A two-part, chemically cured epoxy primer followed by the application of one or more overlying coats of a different two-part, chemically cured epoxy topcoat
  • Two or more coats of the same two-part, chemically cured epoxy coating
  • A single coat of a two-part, chemically cured epoxy coating.

Epoxy linings have excellent water and chemical resistance properties. They can be applied at various thicknesses and are factory applied to provide a dielectric lining. Bonded dielectric lining systems can be applied as either a single- or multiple-coat process. They are tough, resilient, and extremely abrasion resistant, making them an optimum choice for high internal velocity service environments.

Epoxy linings, though, have some specific limitations that must be considered prior to application. A critical performance factor to all linings is the required surface preparation of the metal. In most cases, use of a SSPC-SP 10/NACE No. 2 near-white sandblast with a nominal surface profile of 2-3 mils is required for proper adhesion. Minimum curing times and temperatures must also be closely followed and can range from hours to days depending on the lining formulation.

For field application, epoxies are typically applied by airless spray or brushed onto the pipe. They are considered to be barrier linings, requiring 100% continuity to achieve adequate corrosion protection. Any discontinuity can result in corrosion unless a cathodic protection system is also employed on the pipeline.

With proper surface preparation, controlled application, and conformance to strict curing procedures, thin-film epoxies can provide a strong and chemically resistant durable lining.

Fusion Bonded Epoxies

Fusion bonded epoxies are a one-part, heat-curable, thermo-setting epoxy. FBEs are applied to heated parts in a powder form (10-40 mils) that rapidly gels from liquid to a solid. They are commonly used on steel pipe, provide excellent adhesion to the metal surface, and are resilient coatings that resist damage during handling. FBEs are considered environmentally friendly since they contain no volatile organic
compounds.

Figure 1. Pipe stands on centrifugal pump piping.

FBEs should be applied immediately following the heating process to avoid excess pipe cool-down since the epoxy may not fully cure if the pipe cools below 450°F. The powder is generally applied using semi-automated application rings, electrostatic guns, or flocking units to a minimum finished thickness of 14 to 16 mils.

The FBE material is generally applied in several passes of 2 to 5 mils each and should always be completed in such a manner to avoid possible lamination between layers. The FBE will usually be dry to the touch in less than a minute and fully cured within three minutes depending on the specific formulation of the material. Subsequent handling and testing can begin once the applied coating cools to approximately 200°F.

Polyurethane

Aromatic polyurethanes are 100% solid materials that also contain no volatile organic compounds. Polyurethane linings are typically applied at 20 mils of minimum thickness, but thicker lining applications are possible. Specific to the internal surface of potable water pipes, polyurethane materials offer the following advantages:

  • Fast curing: Ensures economy of high production rates and efficiency.
  • Excellent adhesion to ferrous and properly prepared steel surfaces.
  • High impact resistance.
  • Effectively protects the pipe from corrosion.
  • Lower lining thickness is required compared to other methods; thus the pipe design can be more efficient, reliable, and economical as product waste will be reduced. This results in a higher pipeline capacity for the same nominal size of pipe.
  • Reduced pumping head due to lower head loss from a smoother surface and greater internal area of the pipes.
  • Longer economic life as deterioration due to erosion cavitation is low.

There are also some limitations associated with polyurethane material when used for lining steel water transmission pipe. Polyurethanes require heated, plural-component equipment and qualified and experienced applicators. Polyurethane coatings require the host pipe to be thoroughly cleaned. For in-service pipe, that includes removal of existing hard deposits, nodules, scale, corrosion, and other debris. It also must be dry prior to application of the coating to ensure good adhesion between the liner and the pipe wall.F

Figure 2. Flexible couplings on engine-driven pipe.

Voids and blisters may form if the pipe is not properly prepared and there is a potential for uneven liner thickness due to inconsistencies in dual material component pumps associated with the application equipment.

Aboveground and Pump Station Piping

Piping into or out of a pump doesn’t usually present any severe operational or troubleshooting problems. There are exceptions, of course, and these exceptions can result in serious pumping system problems if not addressed.

The most common problems associated with piping are strain on a centrifugal pump casing or discharge head for a vertical turbine pump, expansion or contraction, leakage, or corrosion due to electrolysis or galvanic action.

As is the case with valves, the best way to prevent troubleshooting problems with piping is to avoid problems in the first place. This needs to be done during installation because if problems arise in service, the result to the pump or system is quite often beyond a simple fix.

Strain on the suction or discharge ports on a centrifugal pump case is most often a problem associated with a pumping system with rubbing or interference between rotating and stationary components. This results in potentially severe wear and damage to the pump impeller, wear rings, bearings, or volute. In addition, an extreme external load on a volute or discharge head of a vertical turbine pump can cause the pump to vibrate and run in a bind.

Generally, except for very shallow sets, strain on the discharge fitting of a submersible pumping system will not cause undue force onto the pump discharge. In extreme cases, excessive strain can result in damage or failure to intermediate pipe joints in the well. Manufacturers design their pump volutes or discharge heads to handle little, if any, external weight or vertical force caused by the connecting piping.

Unsupported valves, long lengths, or heavy piping can impose a direct strain onto a cast-iron volute or case. This strain can often cause a distortion of the running stuffing box surfaces, especially packing or mechanical seals—resulting in premature wear and an earlier overhaul. In severe cases, loads can be high enough to result in cracking and total failure of the volute or head.

This strain was never intended to be imposed on the pump. Failure to correct the condition will continue to result in premature overhauls and a possible failure.

An excellent example of the potential impact of piping strain or valve weight to an end-suction centrifugal pump is illustrated in Figure 1. This is a 4000 GPM at 60 feet TDH booster pump application with a 75 HP electric motor.

In this photograph, it is observed that the weight of the valves and suction and discharge piping is supported at strategic locations using fabricated pipe stands and does not impose any load onto the pump whatsoever. This particular application also used an oversized volute, which required separate support of the volute to the floor as well as the motor itself shown on a steel fabricated base.

Another potential problem often experienced with a pump volute or discharge head is exceeding the rated working pressure of the component. This is most often associated with pumping systems that make use of an inline pressure-regulating discharge control valve used on a fixed speed pump and is fairly common on retrofit pumping systems where a control valve is placed onto the discharge of an existing pump.

As the valve closes during normal operation, the resulting backpressure increase with a steep pump curve can result in dangerous and damaging pressures. This can be particularly hazardous when applied to a 125-pound rated cast-iron volute or discharge head. Many repair cycles to individual pumps have been performed with the ultimate cause never fully discovered, while it should have been obvious the entire time.

Knowledgeable and experienced troubleshooters will always examine all elements of a pumping system and remember that all components must work together in relative harmony for the system to function correctly. Correction of a piping strain involves an examination of the vertical weight exerted onto the suction or discharge connection flanges or threads (often referred to as nozzles) of the pump.

Oftentimes, disconnecting the suction and discharge nozzles and observing the relaxation or movement of the pump or piping can aid the technician in identifying and correcting the problem. Disconnection of either side should result in little or no movement of the pump or piping. Installing secure and adequate supports under piping and next to both nozzles before connecting the pump to the piping can help avoid piping strain.

Another problem that occurs most often with piping exposed to high temperature or pressure differences is expansion and contraction. Just as with piping strain, expansion and contraction can cause a severe external stress to be placed on the pump that it wasn’t designed for, resulting in distortion of the volute or components. This can lead to binding or excessive wear of close running tolerances, such as bearings or impellers/wear rings.

Situations that include long lengths of piping operating at high temperature changes are common culprits for this type of problem. In severe cases, the stress exerted by the cycling changes of expansion and contraction of the piping can cause cracking or failure of the pump case.

Situations such as these must be individually evaluated and the use of appropriate expansion/contraction couplings or piping loops must be provided to prevent transference of undesirable stresses onto the pump. Flexible elastomer pipe couplings, such as Metraflex styles using a rubber bellows, is often an excellent way to accommodate pipe stress and pump vibration. When properly applied and installed, these couplings are useful in limiting the transference of pump or driver vibration from or to the piping and thermal or pressure expansion from piping onto the pump. They are especially useful when installed on the suction and discharge sides of engine-driven booster pumps. See an example in Figure 2.

The couplings help absorb the vibration cycles imposed by the engine to prevent fatigue of the piping, particularly at interconnecting pipe joints. However, the technician must be aware of the potential expansion and distortion of the rubber element under pressure if retrofitting into an installation. This usually must be restrained by using tie-back bolts or some other method of thrust restraint.

Electrolysis and Galvanic Action

Figure 3a. Typical piping support methods.

Finally, problems associated with piping include corrosion due to electrolysis or galvanic action. At times, this condition will lead to unexpected failure of the piping at critical locations, resulting in undesirable leakage or system failure. Technicians who observe frequent or premature corrosion and failure of piping—or most notably at piping joints such as welds or threads—should carefully examine the system for possible electrolysis.

Electrolysis and galvanic reactions are similar terms with similar results, but they differ. Electrolysis refers to a process where an electrochemical reaction causes a very low current flow to occur to a metal due to an external source. A galvanic cell or action causes a current flow to occur spontaneously due to the effect from dissimilar metals being connected together.

Both of these processes can result in corrosive effects to piping, welds, threaded and flanged joints, in addition to the pump material itself. Most corrosive effects to cast-iron pump cases are caused by a similar process known as graphitization where the cast iron tries to return back to its original state of elemental iron.

Figure 3b. Pipe support methods.

Electrolysis in a piping system can be caused by an induced voltage into the piping from the electrical system. This is the result when different voltages (often called potential) are created within a system due to differences within the grounding or neutral conductors. If an electrical system is not properly grounded and bonded, an implied value of current can be routed through the piping network in the attempt to find a grounding path. This low value of current can result in voltage differences resulting in an attack on the piping material. The process not only can be detrimental to the piping but can be dangerous for anyone who might come into contact with the piping if it was disconnected or compromised.

In some instances, this process is used as a helpful one to prevent corrosion of large steel tanks or vessels by sacrificing another metal instead of the tank shell. This process is known as cathodic protection.

Electrolysis in a piping system is best avoided by working with a qualified electrician or corrosion technician to verify that the electrical system is properly and effectively grounded and bonded, the piping is not being used as a primary method of grounding, and bonding jumpers are used around joints that may hamper the proper flow of current.

Although bonding the electrical system to the piping is often required by code, technicians and troubleshooters must remain aware of any undue corrosion that may occur due to incorrect system grounding or bonding. This is particularly important on piping systems using copper pipe or tubing.

Galvanic action to a piping system is caused by placing dissimilar metals together in a piping system. The result is usually rapid corrosion of one of the metals, and slow if any corrosion of the other metal.

The best prevention against galvanic corrosion is to avoid placing metals together that are too far apart on a scale known as the galvanic scale. This scale lists metals, known as anodic (least noble) such as aluminum and steel on one end and cathodic (most noble) such as gold or stainless steel on the other.

In lieu of avoiding placing dissimilar metals together, other less successful methods such as coatings and using welded-over threaded joints may help.

Learning the basic theory of metal corrosion—including the concept of anodes, cathodes, electrolytes, electrochemical reactions, and the galvanic scale—can go a long way in helping a troubleshooter with solving corrosion problems. Ultimately, corrosion problems in a piping system can be a confusing and difficult problem to solve. In more extreme cases, using a qualified corrosion or mechanical engineer may be necessary when all other simpler methods have failed.

Support Brackets and Bases

Without adequate support bases under the piping, valves, pump, and driver, the unit will vibrate and soon fail. Too many cases of inadequate support under a centrifugal pump or driver have caused numerous problems with the unit itself. This includes excessive wear of running surfaces, vibration, and noise, often leading to premature failure and breakage.

Although this is also important for a vertical turbine pump, it is critical for centrifugal pumps. Generally, sizing of the support base for the pump and driver is the job of the design engineer, but new installations or retrofits require the technician to become his own engineer in many cases.

In most cases, the answer to adequate support is vested in two words: mass and support. Mass, simply put, is weight. The more resisting weight that you can provide for the pump to rest on, the less likelihood that it will start to walk to China! Support pads should be placed under the driver (usually an electric motor) with adequate depth below the floor elevation to rest on undisturbed soil under a compacted gravel base.

In many instances, a separate means of support will be needed to support a heavy or eccentric volute. Obviously, when I discuss mass, I also assume that adequate methods of securing (bolting) the pump to the platform have been provided.

Typically, piping and valves should be supported as close to the suction and discharge as practical. In many cases, logistics and space considerations will necessitate placing of pipe stands, as shown in Figure 3a, under the pipe itself and offset from the pump. This may be sufficient if the discharge assembly (piping, check and throttle valve) is fairly lightweight and the pump volute can handle one-half the span weight of the assembly without imposing a distorting or excessive load onto the volute. This is particularly valid for volutes constructed from ductile iron as shown in the figure.

Heavy valves, particularly check or control valves, can impose a substantial burden onto a pump case or volute; thus, a separate means of support should be provided under these devices even if the adjacent piping is independently supported. In order to prevent beam failure or shear of piping—especially thin-walled, large-diameter piping—pipe supports or cradles should support no less than 120° (one-third) of the pipe’s circumference. See Figure 3b for typical support details.

Designer/Client Preference, Cost, and Tradition

Beyond all the hype associated with the technical aspects of piping selection, likely the most important consideration in deciding which type and class of piping to use is designer or client preference based on standard specification, cost, and tradition.

The preference of a designer or client and past comfort with using PVC instead of HDPE or ductile iron instead of steel, for example, plays a huge role in determining which pipe to use. This is often the case when factors such as corrosion or encrustation are considered or with clients who refer to published “standard specifications” that detail the permitted type of pipe, pressure class, and connection means that are allowed for specific projects.

This decision criteria often trumps even technical merit of using one type or size of pipe over another. One of the primary reasons this selection choice is practiced so much is the advantage of uniformity gained by using the same type of new pipe and replacement components.

This can drastically cut back on needed inventory of replacement and service components and predictable costs, as well as provide comfort to the client for the expected service performance and life based on prior experience.

Another area that client preference often plays a huge role is in sizing and pressure rating. Once again, use of a uniform pipe size and pressure rating permits maintaining a lower inventory as well as knowing that replacement components will fit easily into the same space occupied by the existing equipment.

My experience and personal opinion of this factor is simple: So long as there is no technical objection to use of the client’s preference, even if the cost is somewhat higher, I will generally yield to their judgment.

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This wraps up this edition of The Water Works. In the next installment, Part 3, we will continue this discussion on mechanical equipment with an overview on the various types of valves used in water service.

Until then, keep them pumping!


Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 40 years of experience in the water well business, specializing in engineering and business management. He can be reached at epbpe@juno.com.