efore we leap right into the fine details of specific product data and what-makes-it-tick material, I want to devote this first section in the series to the coverage of what I call "The Big Picture." Of all the sections in the course, this could well be the most important for many readers, because it will paint you a picture of the "forest" in which all the individual products are the "trees."

I guess I see this approach as important because of my own first work experience in our industry.Years ago, one of the numerous jobs I had while working my way through college was located in the machine shop of a well-known plumbing manufacturer. My skills at that sort of work were nonexistent when I started, as was my knowledge of plumbing products. Understandably, I wasn't given a heavily responsible assignment initially—the job simply involved loading brass castings into a massive multiple-turret machine, and unloading the components when the operations were completed.

On my first day on the job, the foreman might well have figured that my function didn't warrant more than a cursory explanation of how to load and unload the machine, and let it go at that. Instead, he wisely began by taking me to some remote corner of the plant, showing me the product that incorporated that casting, and explaining what it did and how it worked. The walk and the chat took us all of 10 minutes, and then I was back at the machine, loading and unloading castings for the rest of that night, and for a full year of nights to follow.

"Given the variety and complexity of our industry's inventories, any product education series runs the risk of presenting too much too soon. So in this first section,we'll step back to take an overall look at a typical residential plumbing system. In describing its workings and basic components, this will also give you a topic-by-topic preview of the course to follow."

I spent a lot of those nights thinking about how that product worked. And many years later, returned to that plumbing manufacturer's plant, this time as a consultant with the job of redesigning an aspect of that very product. Not long afterwards, designed an entirely new approach to that category of product, which has since gone into production by another manufacturer.

What's the point of relating this personal experience? Just this: Though I couldn't swear to it, I suspect that those 10 minutes of explanation about where a component fit into the big picture had far greater meaning for me than either that foreman or I could have imagined that night years ago.

The experience has also made me a firm believer in the "big picture" approach to training. As we continue through the course, and as you deal with product facts on a day-to-day basis, it will be helpful to come back to this perspective from time to time. Often, the fog of a particular issue will clear when you remind yourself of the place or function

What's the most basic thing you could say about plumbing?

"Plumbing is a system of bringing fresh water to points of usage, and taking waste water away from those points."

Or, if we want to be a little more sophisticated in our wording, "Plumbing is the system or means of handling fluids — particularly water."

Now quickly, let's qualify that second statement. Yes, a plumbing system can involve transmitting fluids other than water. Certainly, industrial applications give us many examples of this—transmitting of chemicals, food processing, and the like. But let's start simple. I think we'd all agree that by far the greater portion of products sold by the average plumbing supply house relates to the transmitting of plain old water. So that's where we'll begin, and that's how our two definitions will stand until we expand on them in the installments to follow.

For now, we want to highlight the components of a water plumbing system, while at the same time, give you a topic-by-topic overview of the course that will follow in succeeding sections. Since even "water plumbing" isn't as simple as a single definition will provide (there are residential and commercial/ institutional versions), we'll be taking the simpler

Perhaps the most basic aspect of a plumbing system in a home or building is the separate conduits that bring the fresh water in to serve the points of outlet and take the waste water back out again. Not too surprisingly, this also matches our overall definition of a plumbing system pretty closely. The words we use here are "pipe" and tubing," but you sure can't stop at that, because these words can mean a dozen or more different things.With piping, for example, two major areas of distinction have to do with the functions of each -- supply or drainage.

SUPPLY PIPE-WATER IN: Supply pipe is just what the name says—it supplies fresh water to the water-using equipment in the building. Another term often used here is "pressure piping," which helps emphasize the difference between supply and drainage types of piping. In other words, supply piping is designed to withstand a specified level of internal pressure, let's say for example, 200 psi.

Demands on supply piping are therefore far more severe than those on drainage piping. It may further help you to understand the difference by thinking of supply piping being fed by a dynamic force that is constantly trying to push the water through it, say by means of a pump or elevated water tower (the latter providing pressure through the combined factors of height and weight of the water, called "head").

Another difference between the two types of piping is that in most installations, supply piping branches into a dual system, to provide both hot and cold water. A final difference is that the supply piping system is always closed, except when one of the outlet devices is being used.

Supply piping is currently manufactured from a variety of materials, the most common being steel, copper and plastic. (Note #1— Though there is such a thing as "copper pipe" which can be threaded in the same manner as steel pipe, most copper used for transmitting water in plumbing today is what we call "copper tube," which is commonly soldered or brazed together. Note #2—There are a variety of specific materials used in the "plastic" category, but for now, we'll just state this in a general way.)

DRAINAGE PIPE—WATER OUT: Unlike supply piping, drainage piping does not have a dynamic force behind it, and it is always open to the atmosphere. If you think of the old adage, "down the drain," you'll get the picture here. For most installations, gravity simply causes waste water to flow downhill, (though there can be more sophisticated systems that provide mechanical assists in certain applications).

Typically, you will see drainage piping included under the broad and more common category heading of "D-W-V." Now, in case you might have thought that this was some kind of disease or subversive organization, or perhaps a German car, let's set the record straight. DWV simply stands for "Drainage" (or "Drain"), "Waste" and "Vent" piping (kind of disappointing, isn't it?).

While this term describes a "system" in a general sense, DWV can also have a specific meaning when used in reference to copper tubing. There are several grades of copper tubing furnished by manufacturers in this country, one of which is commonly called DWV. This is a thin-wall variety that is designed for drainage-waste-vent applications only—never pressure installations. So here again, always be certain to clarify your terms when "DWV" comes up. Does the customer mean DWV copper, or some other material to be used in a DWV system? Generally, the following elements are what a DWV system includes.

PRIMARY DRAINAGE: In the overall DWV system, the main stack and building drain serve as the heavy-duty portions. This is the piping that is used in carrying waste from toilets, as well as acting as main arteries for the collection of all waste water and solids, carrying them out of the building to the connecting sewer or septic system. The portion of the overall drainage system that serves toilets (more properly called "water closets") is the main stack, best defined as the vertical drainage channel. Every house or building must have least one main stack.

Though there can be several horizontal channels for waste water, depending on the number of floors in the building, there is only one primary horizontal drainage channel, and that is the one at the bottom of any building, called the "building drain" or "house drain." (When I say "horizontal," I don't mean that in an absolute sense—there has to be a slight downward pitch to facilitate draining.) The building drain collects all the waste water from the building, and transmits it to an outside connection with the municipal sewer or septic system.

In relation to waste and vent piping, the type used for main stacks and building drains is always relatively larger because it must permit the free flow of waste from toilets without restrictions that could cause clogging. Whether used in a main stack or building drain, the type of piping used for either portion is the same— a DWV variety. Within this category, the most common materials used today are cast iron, copper and plastic.

This brings us to a point that is often confusing to newcomers in our industry. Probably the most common specific term used interchangeably with DWV, main stacks and building drains is "soil pipe." (Likewise, you will often hear the terms "soil stack" and "soil vent.") It is important to understand that, in common practice, these terms are synonymous only in the specific sense that soil pipe is a cast iron variety used for such DWV applications. Technically, there is no such thing as copper or plastic soil pipe. Instead, the copper or plastic equivalents to soil pipe are simply called DWV piping in their respective categories (DWV copper, DWV plastic, etc.).

And finally, there's one more area of distinction concerning soil pipe you need to be aware of—the two basic designs available. The traditional configuration is called the "bell and spigot" or "hub" type (male and female connections).The newer entry in this field is "no hub" or "hubless" soil pipe.We won't get into the details of the differences here—simply be aware that there is this difference, and be sure to clarify the terms whenever you are uncertain what the other guy is talking about. Frequently, when the simple term, "soil pipe," is used, it is assumed that the "hub type" is meant, but it's always a good idea to specify which type you mean to avoid unnecessary confusion.

WASTE PIPING: Waste piping is similar in function to the piping used in main stacks and building drains, except that it serves fixtures other than toilets; that is, it will not handle human waste. Years ago, houses were commonly built with a separate waste stack from the main stack, with the waste type emptying into an outside grease trap.Today, we continue to use "waste piping" as a separate term, but the concept has changed a bit in the sense that drainage routed through this portion of the DWV system is connected to the main stack and/or building drain, to exit the building in common with toilet drainage.

Waste piping is typically smaller in diameter than the main stack and building drain piping, and is used to carry waste water from sinks, lavatories, tubs, showers, laundry tubs and washing machines.

VENT PIPING: To the average person, vent piping is probably the least understood aspect of the DWV system. Its first function is easy enough to grasp: A vent allows gasses and odors that accompany waste water to leave the building through a chimney-like stack through the roof.

The second part of the story perhaps will require you to jog your memory back to your high school physics class. Remember those experiments that demonstrated the function of atmospheric pressure in assisting the flow and movement of water (like the one where water wouldn't drip out of a hole in the bottom of a can until you opened the top)? Well, you probably thought you'd never find a use for all that stuff, but here it is!

First of all, strategically placed openings to the atmosphere in a drainage system allow waste water to flow easily down the system without burping up the air being displaced. The waste flows down its channel, while the displaced air and gasses rise up theirs—and there's no gurgling interference between the two.

And most importantly, we want to keep a portion of the waste water in low-bend areas of drains called "traps" to prevent gasses from entering the building. Vents therefore serve the important function in preventing the trap water from being siphoned out as the flow of water falls to a level lower than the drain. Without a vent, a vacuum would be formed every time you sent water down the drain, which would empty the trap and allow gasses and odors to escape into the house. With a vent, a vacuum cannot be formed (meaning that siphoning cannot take place), so the waste water simply runs down the drain, maintaining the water seal

This is another area where the terminology can throw you. What we're talking about at this point is pipe fittings.There is a fairly common usage of the word "fitting" which refers to the category of faucets and other accessories used on plumbing fixtures such as sinks, lavatories and tubs. That's something we'll cover under a later heading. To give you a concise definition of pipe fittings, we'll use this:

"Fittings are the components of a piping system that join the sections of pipe together."

Though there are as many basic types of fittings as there are types of piping, all types share common functions. Fittings that provide a bend in a line are called elbows, or "els" for short. Fittings that permit a branch off the main line are called "tee's" or "wye's." To reduce the diameter of the piping from one size to another, there is the "reducer." Closing off a pipe end can be accomplished with a "cap." For a quick-disconnect joint in a piping line, a "union" or "flange" joint is used. There are more fittings than these available with most piping systems, but this gives you the ones common to most piping systems today.

The means of connecting these fittings relates to the basic piping system used in each case. If the piping is the threaded type (typically steel), then the fittings will have corresponding threads. If the piping is copper, the fittings will be soldered or brazed into place. And if the system is plastic, the fittings may be solvent welded, one of several approaches

Though this category of products serves the drainage system, it is not usually thought of as part of the basic DWV net-work of a building. It might help to think of these components as the linkage between sinks and lavatories, and the drainage piping. In material make-up, tubular goods are commonly furnished in either thin-wall brass (chrome or rough), or in several varieties of plastic.

While there are numerous components to take care of all the different installation requirements, tubular goods are probably best known for the "trap" configurations. As we mentioned in our discussion of vents, traps are an important part of the drainage system in that they maintain a seal of water beneath fixtures to prevent gasses and odors from escaping into the building. The most common styles of trap used beneath sinks and lavatories is the "P" type, which joins a drain line back through the wall. ("S" traps are no longer allowed by many local plumbing codes, since this type does not permit as good a venting provision as the "P"

This heading is not a common industry term, but one I have coined to cover the two basic types of devices used to control water in a supply system—valves and faucets. Now, in a purely technical sense, faucets are valves; but in general use, the word "faucet" tends to mean a point of water outlet, whereas "valve" usually refers to a control device in the piping line, located at a point other than an outlet.

FAUCETS: Faucets today are available in two primary categories—two-handle and single-control (frequently called "single-lever" or "single handle," as well). The names pretty well tell the story of the design and function in both cases. Two-handle faucets provide a separate handle for turning on individual hot and cold water supplies, whereas single-control units have one lever or knob for use in selecting both temperature and volume setting.

Beyond this, you should be aware of the various models of faucets available for each type of application in both homes and buildings.

The following are the most common:

1. Kitchen Sink Models-Sometimes called "deck" units, most today are the top-mount style, mounted on 8" centers (holes located 8" apart, center to center).
2. Lavatory Models/Centerset Type-This is a top-mount style, mounted on 4" centers.
3. Lavatory Models/Spread-Centers Type-Also sometimes called 8", 10", 12" centers type, this style separates the handles from the spout, concealing the connecting waterways beneath the fixture.
4. Tub and Shower Models-Unlike the above models, this type is installed into the wall rather than mounted onto a fixture. Though such models are typically called "valves," they are usually grouped within an overall "fa ucet line" of products.
5. Bar, Laundry Models-Most such units are made to mount on 4" centers, though there are some bar models which mount on a single center shank.

VALVES: The subject of valves is a bit more complicated than other product categories. Here we're not so much looking at a matter of "where it goes," as we are "what it does." In other words, because the applications are varied, there is more than just one basic valve design available to do the job.

For purposes of this overview, I have divided the category into two basic sections: General Application and Special Application valves.

General Types-In this area, there are two basic criteria of application to look for:

Is the valve needed for simple "on-off' usage (no in-between settings)?
- or -
Is the valve needed to throttle flow (reduce flow to less than full capacity)?

As you might guess, throttling valves also provide the on-off function, but the primary identification is really that of throttling. With most general application valves, there is another factor that goes hand-in-hand with these first criteria, and this relates to the restriction characteristics of the internal passage-way. Typically, valves recommended for "on-off' usage only provide full-flow characteristics (or close to it), with little restriction or cavitation that would result in pressure drop.Valves that are suited for good throttling characteristics, on the other hand, most often do not provide full-flow internal passageways.

Note—Keep in mind that these are extremely general statements at this point, simply aimed at giving you an overview. When we get into the detailed section on valves we'll cover the various designs in depth.

One further note—if these are valves, what are "stops"? There is a type of valve, called a "stop," which is used in conjunction with certain fixtures. Its purpose is to cut off (or "stop") the supply of water leading to that fixture so that servicing can be accomplished without need to turn off the water supply to the entire house or building during the process.

Most stops use a compression (washer) type of valving, though today, there are ball valve mechanisms used, and in few cases, ceramic valving. But most stops are the same on the inside, outside they come in a variety of configurations to adapt to the numerous connection requirements. As an example, if the piping leading to a fixture is 1/2" threaded steel, and the riser to be used in connecting to the faucet is 3/8" copper, your stop valve must accommodate one type of piping at its inlet, and the other type at its outlet. It is very important to get the specific definition straight when dealing with customers, since the simple term "stop" can include straight and angle versions, each with numerous combinations of inlet and outlet configurations and sizes.

Special Application Valves—As the heading suggests, we are using the term "special" to cover all types of valves that are not included in the general application category. Each has a special design and purpose, which we'll explain briefly as follows:

1. Check Valve—This device allows the water to travel in one direction only, in cases where reversal would be undesirable. A common example is found on the drain outlet of a sump pump.When the pump shuts off, you don't want the water then in the piping to drain back down into the sump, so a check valve blocks the passage the moment the flow changes direction. There are also applications of this type of valve on supply lines.
2. Pressure Regulator—Often called Pressure "Reducer," this is a rather sophisticated mechanism that throttles pressure, maintaining a selected output lower than the incoming pressure being supplied (the unit can never deliver more than the pressure being supplied to it). Pressure regulators are used for a number of reasons, a common one being to reduce excessive pressure supplied through certain municipal water systems, which can be abusive to the plumbing system of a home or building.
3. Safety Relief Valve—This item is also called "Pressure Relief Valve," "Temperature Relief Valve," and "T & P Valve." I like the word "safety" as a name, however, because that pretty well tells the story of what it is. Whenever you heat water in a contained area, resulting in locked pressure, you have a potentially dangerous situation unless some safeguard is provided. Though the basic controls on water heaters and boilers are quite reliable today, there is still the possibility that a malfunction could cause an explosion of the tank. A safety relief valve is designed to open when internal temperature and/or pressure exceed a given point, blowing off steam and/or water until internal pressure is lowered to the normal range.
4. Toilet Control Valves—There are two basic types of valves used in the flushing of water closets. Each relates to the basic flush system employed:
   1. Ballcock (sometimes called "fillvalve")—This type of valve is used with tank-type water closets. Once water in the tank has been released to flush the bowl (by a separate valve), this mechanism is activated to refill the tank. Until a few years ago, activation was commonly accomplished by the familiar float-and-rod approach, but in recent years other types of float and actuation have been introduced.
   2. Flush Valve—This type is used with toilets that are supplied with high-capacity piping (and thus, high-volume water), eliminating the need for a storage tank. A flush valve delivers a predetermined amount of water (through a timing factor called "metering") to flush the bowl, then automatically shuts off. Unlike the tank type, it does not require a refill period before it is ready to activate again. Flush valves are used predominately in commercial/institutional installations, and are seldom found in residential applications.
5. Sillcock (sometimes called "hose bib")—In the sense that this is a valve located at an outlet location, it could be classified as a "faucet." Equipped with special spout threads for hose connections, sillcocks are commonly used in outdoor applications (such as for yard and garden service). Many sillcocks sold today feature a "freezeproof' provision, involving an elongated housing which locates the actual valving inside the wall of the house, with handle and spout outside the wall.
6. Vacuum Breaker—A device somewhat related to the check valve in function, in that it is used to prevent the reversal of water flow, the vacuum breaker is specifically intended to prevent the introduction of contaminated water into supply lines.Without getting into the physics of the whole "back-siphoning" phenomenon at this point, let's just say that a vacuum breaker activates at the moment the water flow reverses direction, opening the line to atmosphere at that point, and halting any possible siphonage.
7. Thermostatic Valve—This product delivers water at a preset temperature level, adjusting for variations in inlet levels (though it cannot deliver water any hotter or colder than the extremes provided by the supplies).As an example, if the unit were set for 95∞F., it would adjust the mix of the incoming hot and cold water supplies automatically to produce that output.
8. Pressure Balance Valve—Also called Pressure Compensating or Pressure Equalizing, this type of valve is concerned with maintaining a relative pressure between supplies. A by-product of this basic function is the maintaining of consistent outlet temperatures (assuming that inlet temperatures remain constant), accounting for the occasional confusion of this product with thermostatic valves. In a nutshell, here's what happens in a pressure balance valve: When the inlet pressure of one supply line changes (either the hot or cold side), the mechanism automatically alters the output of the other supply to maintain the same relative mix, and thus, the same temperature. So, if you were taking a shower while someone flushed a nearby toilet, for example, you would be protected against a sudden hot blast. Your overall flow would drop, but your temperature would stay the same.

Other Types Of Valving—While this covers the majority of the "bread and butter" valves commonly used within our industry, there are still others, more specialized, which have not been included in this overview. If your pet valve design hasn't

Again, I'm using a word here, not because it is commonly used in our industry, but because it might help you to define another group of products.The ones we will include in the section below may not seem that logically related to one another, but they all share one common characteristic: They all do something to the water.

WATER HEATER—Obviously, what this "does to the water" is heat it. Few plumbing systems of any kind today are designed without this provision. Traditionally using fuel or electricity as the source of heat, these systems can take the form of freestanding units, or, in the case of commercial and industrial applications, can be provided as part of the overall heating plant of a building. One of the most recent new developments in this product field is the use of solar energy as either a primary or secondary source of heat.

WATER SOFTENER—Though this is the most familiar term, a more "proper" one is "water conditioning system." The need for such a system can be regional, depending on the level of "hardness"—the amount of calcium and magnesium—in the local water supply. Since the unwanted minerals take the form of "ions," a softener is designed to attract and thus remove these from the passing water, ex-changing them with ions of sodium.

Commonly, two primary tanks comprise a softening system: 1) the exchange tank, where incoming water passes over a granular substance to perform the basic function of removing the calcium and magnesium, and 2) the brine tank, where a salty solution is kept for the periodic process of regenerating the exchange tank.

WATER FILTER—Some folks confuse the water filter with a water softener, but the products are really very different—both in what they do and, in some cases, how they work.Most water filters today are designed for one of three functions:

1. To remove objectionable taste and odor;
2. To remove sediment, or
3. To remove excessive iron from the water. Iron filters are similar to water softening systems in the sense that there is an ion exchange process that is periodically and automatically regenerated.

The other two types of filter are not self-regenerating, but rather use a "throw-away" type of cartridge element that is discarded when saturated. Because of the limited capacity and lack of regenerating capability, filters for removing taste, odor and sediment are recommended for use with a single outlet only (in other words, serving one dedicated drinking faucet only— not installed at a service line entry to an entire house). In addition to physical filtering, there is a system called reverse osmosis (R.O.) that removes and flushes impurities down the drain. Though self-regenerating in a basis sense, these systems are usually equipped with a conventional filter to remove objectionable taste and odor.

WATER METER—If you're struggling to figure out what this appliance does to the water, how about this—it measures it. Unlike any other aspect of the plumbing system in a home or building, this is one component that is installed and serviced by the municipality or private water company providing the water service (except, of course, when there is a private water supply). The purpose of measuring the water, as you might guess, is to provide a basis for billing the customer for the water consumed. Many current meter models are equipped with provision for

Although a broad and important category, fixtures actually require less depth of coverage in an introductory section of this sort, simply because these are products with which the average person is most familiar. Whether you plan to be a plumbing expert or not, you know what a tub is, what a sink is, and so forth. (If not, you've got problems deeper than this course can solve.) We'll give a brief review of these products for now, but first another word about the general industry term, "fixture."

Though there is no "Roberts Rulebook of Proper Plumbing Terms" that we can cite as our authoritative source, it is generally agreed by industry veterans that the word "fixture" means a water receiving device. As I mentioned earlier, you will sometimes hear people refer to faucets as fixtures. Based on common usage, this is incorrect. We don't make an issue of this to show our superior grasp of our industry language, but simply to straighten out our communications and prevent misunderstandings. I have found this little couplet of a definition to be helpful in keeping it straight in my mind:

A Fixture is a tub, sink, lavatory, etc. which receives the water; a Fitting is the faucet, shower valve, etc. which delivers the water to those fixtures.

Okay, now that we've covered that fascinating background on what we call these products, let's look at some specific examples.

BATHTUB—This is a little more complex than it used to be, with the advent of unitized and modular tub and surrounding wall designs. Today, tubs are available in a variety of materials, though only those belonging in the "plastic" or "fiberglass" category are avail-able with integral enclosure walls. Today, we also have the option of whirlpool.

LAVATORY–Let's clarify another term unique to the internal workings of our industry. Chances are, you have always called this product the "bathroom sink" or "washroom sink," right? And a "lavatory" was the place you went when you felt nature's call back during school days—also right? Boy, did you get a second-rate education! In "plumbingese," we use the term lavatory to describe the wash basin.

SHOWER—While technically, this can mean a framed and tiled alcove for showering, when we speak of shower in the sense of a specific product, we're usually referring to a separate shower stall. This is typically a free-standing unit, including its own walls. The one key component common to both types is the receptor base, the part that goes on the floor to receive the water and send it down the drain.

KITCHEN SINK—Of all the fixtures common to the home, this one probably offers one of the widest selections in terms of styling and design. Sinks today are offered in several basic materials: stainless steel, cast iron, enameled steel plastic and composites (mixture of resins and stone).

WATER CLOSET (AKA "TOILET")—Here's another "plumbingism." We won't bother you with all the exciting history behind this term except to say that "water closet" is our industry's code word for "toilet." In past years, purists often made an issue over the use of the "proper term," but most manufacturers today have swung over to using the same term most people use. To add to the fun, this product is also often referred to by the colloquial names of "commode," "china" or "pot."

LAUNDRY TUB (AKA "LAUNDRY SINK")—or maybe "laundry tray." In other words, here's another product which is known by more than one name.

Reminder: We have not included coverage of fixtures such as urinals, drinking fountains, etc., because this overview has been limited for the most part to residential plumbing systems. Later in the series, we'll explore the field of commercial plumbing products in greater detail. At that time, these items will be given the full treatment—so hang on,

Up to this point, our discussion of the various components of a plumbing system has been presented with one rather basic assumption in mind —that something is delivering the water to that system. In all cases, the "something" involved will be one of two possibilities: 1) service from a municipal or independent-owned utility; or 2) a private water system— usually a well. (Since providing products for waterworks tends to fall within the commercial category, again we will defer discussion of this topic to a later date.)

In the case of buildings and houses served by wells, "private water system" is really more than just a fancy name for "pump" here, because there is more to the average installation than just that. There are actually two basic components in the typical installation—the pump and the pressure tank.

PUMPS—There are two primary criteria to look for here:

1. The location of the pump—above the ground or submerged in water
2. The type of pump—the operating principle involved.

The first criteria is rather self-explanatory, but let's expand on the second part. Probably the two most common identifications of water well pumps today are the jet type and the submersible type. Unfortunately, this gives you an "apples to oranges" match-up, since the first one tells you something about the operating principle involved, whereas the second tells you where that type is installed—down in the water. Actually, the two types are pretty closely related when you get down to the basics of how they move the water, with the operating principle in both cases based on "centrifugal" action, using a high speed impeller.

But here is where the difference comes. Whereas the jet type typically uses a single impeller of a relatively large diameter, the submersible uses a "stack" of impellers of relatively small diameter. Now, there's a whole lot more to this subject than we can cover here, but this gives you a bit of a handle on the basics.

In addition to these most common types of pumps, there are also a few other designs in what is called the "positive displacement" category. These include the reciprocating (or piston) variety, the helical rotor type, and the regenerative turbine design.

PRESSURE TANK: The other basic component of a private water system is the storage tank. In its simplest definition, a storage tank stores not only the water itself, but pressure to move that water through the supply system when called for. (The pressure aspect is made possible through the compressing of air in the tank.) This results in three benefits:

1. It prevents excessive cycling of the pump, protecting the motor from abuse.
2. It permits delivery of water to the outlets between cycles of the pump.
3. It can provide additional pressure and capacity than the pump itselfcould

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   deliver on a strictly "demand basis."

Though this is a "specialty" product in the sense that it is not part of any overall category of products, as an important sales factor in our industry, disposers definitely warrant coverage in this overview.

Food waste (our nice way of saying "garbage") disposers are installed in the outlet of kitchen sinks for the purpose of grinding and pulverizing food waste so that it can be sent down the drain along with the water, instead of being placed in the garbage can. Actually," food waste" is a good word to clearly convey the purpose of this product; or perhaps I should say, to convey the limits of its function.To some people, "garbage" can mean just about anything you normally throw in the trash, including paper, glass, bottle caps, bills—whatever. The common disposer is not designed to handle such items, and really should be used only with food waste materials to insure against damage to the unit.

In terms of basic design and operation, all disposers made today operate on the same principle. Food is dropped down into a hopper containing a high-speed turntable that flings the garbage against "grind teeth" around the perimeter of the chamber. This action pulverizes the waste into particles about the size of rice grains. The cold water running down the drain while the grinding takes place then carries these particles away through the drain system.

Most disposers are commonly activated in one of two ways: 1) by a separate switch on the wall; such models are called continuous feed, since you can keep feeding garbage into the unit while it is running; 2) by inserting the stopper into the throat of the disposer; these models are called batch feed, because you load the hopper with garbage before grinding begins. In addition, there is a deck-mounted air switch offered on some continuous feed models today. The majority of disposers sold in this country are continuous feed models.

Beyond the means of activation, the other basic criterion to look for in a disposer is the motor specification (motor size in terms of horsepower rating). Typically, the inexpensive models use a 1/3 hp motor, while the better