Plumber's Licensing Exam: Water Supply And Distribution

Providing a safe and clean water supply to the population is the cornerstone of modern plumbing. The occurrence of multiple diseases has been minimized, and some diseases have been virtually eliminated through the implementation of modern plumbing techniques. The fact that clean water is often taken for granted in the United States is testament to the success of American plumbing. The plumbing codes of our country will continue to develop, guide, and enforce the provisions necessary to continue this tradition.

Objectives
- Identify materials that are permitted for water supply and distribution
- Calculate the proper size of a water main and water distribution system
- Develop familiarity with the potential contamination hazards present in a water distribution system
- Recognize how electrical grounding can be affected with different piping materials
- State how to maintain sufficient water pressure throughout a water distribution system

Key Terms:
flow pressure
individual water supply

General Rules
The water supply and distribution sections of both the IPC and the UPC cover all the aspects of water supply piping, including the materials used, the design of water supply systems, and the proper manner of installation for water supply systems. The IPC takes special note of the possible effects that a solar water heating system can have on a water distribution system. The IPC starts the chapter on water supply and distribution by clearly stating that any form of solar water heating must be installed in compliance with all of the rules of the plumbing code. This was more than likely done due to the high potential for cross-connections with systems containing antifreeze liquids. In reality, the code regulations contain enough rules to protect water distribution systems from cross-connections—one particular application should not be singled out as a potential cross-connection offender when the problem can occur almost anywhere. However, with any unfamiliar system, it is a good idea to be aware of the possible dangers that can occur with the application. (Refer to IPC 601.0–603.0; UPC 601.1–601.4)

Real-Life Situation: Sophia, the estimator at Ace Plumbing Company, is earning her pay again this week. Converting the old Williams Hardware building into apartments is going well, but the size of this job requires thinking beyond the usual residential standards. With six apartments, two large washing machines, and one laundry tray, water supply pipe sizing becomes an important issue. Is a 1-inch water service big enough? At what point in the supply train can we reduce to 3/4 inch? These questions must be answered before the actual water supply piping can begin.
Section 601.3 of the IPC requires that metallic water piping used for electrical grounding must be replaced with nonmetallic piping, unless a continuity of grounding is installed that meets with the code official’s approval. This is referred to as bonding the system. Many older homes relied on the plumbing system for electrical grounding, so always be careful! It makes the electrical system not only potentially dangerous for the residents, but also for you while you are working on the system. Imagine cutting an old, leaking section of galvanized pipe. The water drains on the floor where you are standing, and, as the continuity is broken when the flow of water stops, the electricity that used to go to ground through the pipe now needs to find a new path to ground—down your wet arm to the puddle you are standing in seems like a good possibility. Not a healthy way to last long enough to collect your Social Security.
Both the IPC and the UPC require that all buildings equipped with plumbing fixtures that are intended for people to live in must be supplied with potable water at pressures specified. Potable water must be supplied to all fixtures except where gray-water systems are installed in an approved manner. Gray-water systems may become more common as a way to conserve clean water supplies around our country and the world. The UPC prohibits any connection whatsoever between a potable water system and a reclaimed water system. Even an approved backflow preventer is not enough of a guarantee for prevention of a cross-connection. Reclaimed water is only allowed to be used to flush water closets and urinals, and as a water supply for trap primers on floor drains and floor sinks.
The spirit of the opening sections of the water supply and distribution chapter of both the IPC and the UPC demonstrates the concern with the safety of water supplied to the fixtures in all buildings. It is a basic premise of modern plumbing that safe, clean water is supplied to the population. It is your responsibility to carry out that mandate.

Quantity
All the fixtures in a building intended for human occupancy must be supplied with an adequate water supply. The source can include any storage capacity on the site as well as the supply entering through the water service from the public system or from the individual water supply system. Before a new supply system or a repaired supply system is placed in service, it must first be disinfected. (Refer to IPC 602.3.2–602.3.5.1; UPC 608.1)
The individual water supply system has some additional rules. The pump must be designed to safely handle potable water. It cannot allow any kind of contamination into the water system. The pump has to be designed to keep a prime, and all parts of the pump need to be accessible. The pump and the immediate piping have to be protected from freezing and any pump installed in a basement must be mounted on a surface that is at least 18 inches above the basement floor. This helps prevent flooding of the pump. A well cannot be located in a pit due to the potential for contamination of the water supply if the well pit floods.

Water Service
In parallel water distribution systems, the hot and cold water piping may now be grouped in the same bundle.
No matter how well designed a water distribution system is, it cannot function well without a properly designed and sized water service. The whole distribution system is dependent on the quality, quantity, and pressure of the water supply through the building’s water service. (Refer to IPC 603.1–603.2.1; UPC 609.2– 609.10.1)

Real-Life Situation: The building that Sophia needs to size the water service for will contain six apartments when it is completed. All of them have one full bathroom and a kitchen sink. Using the table below we can find what the water service fixture unit (WSFU) load is for the building.

The six full bathrooms can each be sized as a bathroom group:
BATHROOM GROUP, PRIVATE, FLUSH TANK 3.6 WSFU
3.6 °— 6 = 21.6 WSFU

Remember that every apartment has a kitchen sink:
KITCHEN SINK, PRIVATE, FAUCET 1.4 WSFU
1.4 °— 6 = 8.4 WSFU

We still have the laundry room with two washing machines and a laundry tray. Let’s include those figures:
WASHING MACHINE (15 LB.), PUBLIC, AUTOMATIC 4.0 WSFU
4.0 °— 2 = 8 WSFU
LAUNDRY TRAY (1 TO 3), PRIVATE, FAUCET 1.4 WSFU
1.4 °— 1 = 1.4 WSFU

Now, add up all the water service fixture units in the building:
21.6
8.4
8.0
+ 1.4
39.4 WSFU

We now know that the total number of water service fixture units in the building is 39.4. The next step is to convert the WSFU total into GPM (gallons per minute). Use Table 8.2 to make the conversion. We must round up our 39.4 WSFU to 40 WSFU to fit the chart. On the chart, 40 WSFU converts to 26.3 GPM.
The next step is to use the third table below to determine what size pipe will carry 26.3 GPM at a velocity no greater than 10 FPS (feet per second). Beyond that velocity, noise and pipe erosion increase dramatically. We can see that a 1-inch pipe will handle the volume and remain under 10 FPS.

Sizing
The smallest diameter water service pipe allowed is 3/4 inch. This refers to the nominal, or inside, pipe diameter as stated earlier in the code. Remember, all pipe sizes referred to in the codes are nominal unless stated otherwise.
The smallest diameter water service pipe allowed is 3/4 inch, but what if you have a building with lots of plumbing fixtures and you know the main will have to be larger than 3/4 inch?

How do we size it properly?

Follow this next example to find out.

Use the tables below to help you.

Installation
When installing the water service and the sewer main for a building, keep in mind that they can be no closer than 5 feet apart if they are buried at the same depth. You are allowed to put both pipes in the same trench if the water service is installed at least 12 inches above the sewer main. This isn’t always possible due to frost depth considerations. If a water main is sleeved at least 5 feet in each direction, it can cross over a sewer main without having to meet the 12 inches above the sewer rule. A further protection of the potable water supply pipe is the prohibition against installing any water service pipe above, below, or through a cesspool, septic tank, or leach field.

The table below gives the distances the water service pipe must be from various components of a sewage system. (Refer to IPC 603.2–603.2.1)

Distribution System
We can now move inside the building and concentrate on the water distribution system to the fixtures within the building. (Refer to IPC 604.1–604.11)

Sizing
The IPC simply states that the water distribution system must be designed according to accepted engineering practices and the method used must be approved. A particular sizing system is not mandated because it is not possible to predict the demands that will be placed on a particular distribution system in any particular part of it at any particular place. (Refer to IPC 604.1)

Pressure
When a system is designed, considerations must be made for the pressures required to operate the various fixtures in a system (See Table). The most demanding fixture is the blowout water closet with a flushometer valve. These require a flow pressure of 25 psig at a flow rate of 35 GPM. That’s why you don’t find these fixtures in residential installations. The water supply pipe must be 1 inch in diameter from the main to the flushometer valve. (Refer to IPC 604.4–604.7)

While we are talking about pressure, we should also mention velocity concerns. The table below, which is IPC Table 604.1, shows the maximum velocity allowed in various materials and sizes. If the stated velocities are exceeded, significant erosion of the pipe material will occur, along with noise in the pipes.

Fact: Head pressure (the pressure created by the vertical height of water) can be expressed as psig by multiplying the height of the water in feet by 0.433.
psig = 0.433 × height

And, if you know the gauge pressure (psig), you can multiply the psig by 2.31 to get the height of the water column.
psig × 2.31 = height

Materials
Many materials are accepted for use as water service pipe by the IPC and the UPC. Some of the most common materials used today are copper, cross-linked polyethylene (PEX), polyethylene (PE), and galvanized steel pipe. Polyethylene of raised-temperature (PE-RT) plastic hot and cold water tubing and distribution systems are now recognized by the IPC. It is important to remember that it is prohibited to install any water service pipe in soil that is corrosive or detrimental to the pipe material. (Refer to IPC 605.1–605.3)
Some of the more common materials allowed for distribution systems within a building are copper, PEX, chlorinated polyvinyl chloride (CPVC), and brass pipe. All piping materials used in distribution systems must have a minimum working pressure of 100 psi at 180°F.

Caution: Translucent piping materials, such as some varieties of PEX and PE, should not be installed where sunlight will strike them. UV rays will break down the molecular structure of the tubing and the tubing can act like a miniature greenhouse and support algae and bacteria growth in the water within the tubing.

Water Hammer Controls
The design of the water distribution system with respect to limiting flow velocities should control a water hammer in the system in general. Where quick- closing valves, such as solenoid valves in automatic washing machines, are used, a water hammer arrestor must be installed. The manufacturer’s instructions for installation are considered part of the plumbing code. (Refer to IPC 604.9)

Installation Criteria
There are several places in a water distribution system that require a full-opening valve. The water service pipe at the curb needs one. The place at which the water service pipe enters the building is another. The outlet, or discharge, side of every water meter, and at the base of all water risers in multifamily buildings over two stories tall are two other targeted areas. In multifamily buildings, every down-feed pipe requires a full-opening valve at its top. The entrance to every individual dwelling needs the full-opening valve. The water supply pipe to a water tank and the cold water supply pipe into a water heater both require a full-opening valve. This is done to maintain control over the system without adding any significant restriction to the flow. All full-opening and shutoff valves must be accessible. (Refer to IPC 606)

Tips
In many jurisdictions, shutoff valves will also be required on the water supplies to tubs and showers. Be sure you are referring to the local version of the plumbing code when you are preparing for your test.
In addition to the full-opening valves placed throughout the building, shutoff valves must be installed on the fixture supply to each plumbing fixture with the exception of showers and tubs. The water supply to every sillcock requires a shutoff valve. The water supply to every piece of mechanical equipment, such as the heating boiler, and every water-using appliance also must have a shutoff valve.
If there is a pressure tank in the water distribution system, it must be equipped with a pressure relief valve rated no higher than the rated working pressure of the tank. Pressure reducing valves are required to be installed wherever the water service pressure is above 80 psi.

Hot Water
The cold-water society ended decades ago. Now, all fixtures that are intended for bathing, washing, culinary, cleansing, laundry, or building maintenance must be supplied with hot water. Tempered water (maximum 110°F) must be supplied to baths and showers. A tempering control other than the thermostat of the water heater must be utilized. (Refer to IPC 607) The IPC prohibits a water heater thermostat from being used as the temperature-limiting device where the code requires a limit for hot or tempered water.
When the hot water must travel 50 feet or more to the farthest fixture, some method of maintaining the water temperature must be used. A common method would be recirculation of the hot water to the water heater either by convection or through the use of a pump, and ensuring that water piping in automatic temperature-maintenance systems is insulated. This is now a provision of the IPC.

Backflow Prevention
The potable water system must be protected against backflow through sound installation practices and the use of prevention devices such as air gaps, antisiphon fill valves, double check valve backflow preventers, barometric loops, and vacuum breakers. Connections to boilers must use a double check valve backflow preventer with a vent. (Refer to IPC 608.1) Potable water supply to beverage dispensers, carbonated beverage dispensers, or coffee machines must also be protected by an air gap or a vented backflow preventer in accordance with ASSE.1022.

Expansion Accommodation
If thermal expansion is likely to occur, some means of controlling it must be installed. Usually a pressure-reducing valve is installed on the water main to control the incoming water service pressure. Many pressure-reducing valves act as a check valve and will prevent water from expanding out through the water service pipe. Therefore, an expansion tank must be installed to absorb any expansion that might occur in the hot water system. (Refer to IPC 607.3)