Water Supply & Distribution — Plumber Practice Questions

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• Potable water travels from the utility main to the point where the interior piping of the building begins. Under the code, what is the correct classification for that buried run of pipe?
• A water service pipe must be sized for the demand of the structure it feeds, but the code also sets an absolute floor on its diameter. What is that minimum nominal size for a water service pipe?
• You measure static pressure at the building of 96 psi with no water flowing. The code limits the static pressure delivered to the building water distribution system. What corrective work does the code require here?
• The code requires devices that absorb the shock wave created when flowing water is stopped abruptly. Under what condition does the code call for water hammer arrestors to be installed?
• The available street pressure is not enough to deliver the required flow and pressure at the highest and most remote fixture outlet. What does the code require the designer to provide?
• The fixtures in a small office total 60 water supply fixture units. The conversion table given for this problem shows that 60 water supply fixture units of predominantly flush-tank demand equals 26 gallons per minute. The same service must also carry a continuous irrigation demand of 5 gallons per minute. What total design flow should be used to size the water service?
• A cold water riser serves five identical apartments stacked one above another. Each apartment contains fixtures totaling 9 water supply fixture units. For this problem, use the given conversion values: 9 water supply fixture units equals 8 gallons per minute, and 45 water supply fixture units equals 24 gallons per minute. What design flow governs the riser section below the lowest apartment?
• Static pressure at the meter measures 62 psi. The highest fixture outlet is 38 feet above the meter. Use 0.433 psi for each foot of elevation. Friction loss through the meter, the piping and the fittings totals 14 psi at the design flow. What pressure remains available at that highest outlet while water is flowing?
• A regulator on the service is set to deliver 75 psi to the lower zone. The most remote fixture in that zone requires 20 psi flowing at its outlet, and friction loss to that fixture totals 12 psi. Using 0.433 psi per foot of elevation, what is the greatest height above the regulator that this zone can serve?
• You are preparing to disinfect a newly installed section of water distribution piping consisting of 240 feet of 2-inch pipe. For this problem, use the given value that 2-inch pipe holds 0.163 gallon per foot. How much water does the section contain?
• A newly installed copper water distribution system must be tested and proved tight before it is concealed. Which test method does the code accept for this piping?
• A new potable water distribution system must be purged and disinfected before it is placed in service. Which chlorination procedure does the code accept?
• An air gap is being used to protect a potable water outlet discharging above a receptor. How does the code establish the minimum vertical distance for that air gap?
• An atmospheric vacuum breaker has been selected to protect a fixture supply against back-siphonage. Which installation condition does the code require for this device to be acceptable?
• An underground irrigation system has electrically operated zone valves downstream of the point of connection, and the supply to it stays pressurized all season. Which backflow device suits this arrangement?
• A potable make-up line feeds a boiler whose water is chemically treated, and the connection remains under pressure with the possibility of backpressure from the boiler. What protection does this high hazard connection require?
• A threaded hose connection on the exterior of a building must be protected against backflow because a hose end can end up submerged. What does the code require at that outlet?
• Cross-connection control requires that potable water never be exposed to a path back from a nonpotable source. Which of the following installations is a prohibited cross connection?
• A wet-pipe fire sprinkler system contains no antifreeze or chemical additive and has no auxiliary water supply, so its connection is classified as a low hazard under continuous pressure. What is the minimum backflow protection the code accepts for it?
• The code requires a shutoff valve so that a storage water heater can be isolated for service without shutting down the rest of the building. Where must that valve be installed?
• The code requires a valve that opens to the full bore of the pipe at a specific point on the incoming water service. Which location does that requirement cover?
• A multiple dwelling is being piped from a single water service. Besides the valve at the service entrance, what additional shutoff requirement applies to the individual dwellings?
• A fixture fitting has separate controls for hot and cold water. The code fixes which side each control is served from so that users encounter the same arrangement everywhere. How must the hot water control be arranged?
• The developed length of hot water piping from the source to the most remote fixture exceeds what the code allows without additional measures. What must be provided so the system complies?
• Discharge piping is being run from the temperature and pressure relief valve on a storage water heater. Which arrangement satisfies the code?
• A storage water heater is installed in a location where a tank leak would damage the building, so a pan is required beneath it. What does the code require of the pan drain?
• A water distribution run measures 140 feet of pipe, and the fittings in that run have a combined equivalent length of 45 feet. The pressure budget leaves 9 psi to be spent on friction loss in this run. What allowable friction loss per 100 feet should be used to select the pipe size?
• Fixture fittings are limited by the code to a maximum flow rate measured at a stated test pressure. What is the maximum flow rate permitted for a shower head?
• Shutoff valves serving a group of fixtures are being installed inside a framed soffit that will be finished with gypsum board. What does the plumbing code require regarding those valves?
• A potable water storage tank is being installed to feed the suction side of a building water pressure booster system. What does the code require of that tank and its fill?
• A hydropneumatic pressure tank is installed as part of a water pressure booster system. What protective device does the code require on that tank, and how must it be set?
• An elevated potable water storage tank is provided with an overflow pipe. How does the code require that overflow to be arranged?
• A hot water circulation system with a pump is installed to maintain temperature in a long distribution run. What does the code require of the pump arrangement itself?
• Heat traps are provided at the hot water outlet and the cold water inlet of a storage water heater. What do those devices accomplish in the system?
• The temperature of the water delivered to a bathtub fill valve has to be limited so a user cannot be scalded. How does the code expect that limit to be achieved?
• A storage water heater is being set in the corner of an attached private garage where a vehicle is parked. What does the code require at that location?
• A storage water heater is being installed in an attic above a finished ceiling. What does the code require so the appliance can be serviced and replaced?
• Threaded hose connections throughout a building are being reviewed for backflow protection. Which statement correctly describes where the code requires a hose connection backflow preventer?
• A chemical dispensing unit injects cleaning concentrate into the water supply serving a service sink, and the connection stays under pressure. What degree of protection does the code require at that connection?
• A wet-pipe fire sprinkler system serving an unheated warehouse is charged with an antifreeze solution and is supplied from the building potable water piping. What backflow protection does the code require at that supply connection?
• Testable backflow prevention assemblies have been installed on the water service and on several process connections in a building. What does the code require regarding testing of those assemblies?
• A building supplied by the public water system also has a private well on the same property. How may the two supplies relate to the building piping under the code?
• Nonpotable piping on a campus feeds flush valves and irrigation zones. What does the code require at the outlets and operating valves of that system so the water cannot be drawn for the wrong use?
• A new potable water distribution system has been chlorinated for the required period and then flushed out. What does the code require before that system is placed in service?
• A gravity flush tank water closet is being trimmed out, and its fill valve discharges into water standing in the tank. What does the code require to protect the potable supply at that submerged inlet?
• Piping is being made up between a storage water heater and the relief valve that serves it. What does the code permit in that connection?
• Static pressure at the meter is 68 pounds per square inch. The most remote outlet is a flushometer valve that requires 25 pounds per square inch of flowing pressure and sits 24 feet above the meter. Take these values as given: the meter loses 6 pounds per square inch at design flow, the reduced pressure principle assembly on the service loses 12 pounds per square inch, elevation costs 0.433 pound per square inch per foot, the developed length of pipe is 180 feet, and the fittings in that run add 60 feet of equivalent length. How much pressure remains for friction loss, and what does that work out to per 100 feet?
• A gauge at the water meter on the ground floor reads 54 pounds per square inch with no water flowing. A hose bibb is located in a basement 11 feet below the meter. Using 0.433 pound per square inch per foot of elevation, what static pressure should be present at that hose bibb?
• A cold water branch must carry 45 gallons per minute. Take these values as given: the design criterion limits velocity to 8 feet per second, a 1-1/4 inch pipe has an inside cross-sectional area of 0.0104 square foot, a 1-1/2 inch pipe has an inside cross-sectional area of 0.0141 square foot, and 1 cubic foot per second equals 449 gallons per minute. What is the smallest of those sizes that keeps velocity within the limit?
• An existing cold water branch was sized for a capacity of 18 water supply fixture units, and the fixtures on it today total 12.5 water supply fixture units. Take these values as given: each added lavatory counts as 1 water supply fixture unit and each added flushometer valve water closet counts as 10 water supply fixture units. Which addition can that branch still carry without being resized?
• A newly installed section of water main holds 480 gallons, and the disinfection procedure calls for a chlorine concentration of 50 parts per million. Take this value as given: 1 gallon of 5 percent sodium hypochlorite added to 1,000 gallons of water produces approximately 50 parts per million. How much hypochlorite does that section require?
• A hydropneumatic tank has a total volume of 86 gallons. Take these values as given: at the selected cut-in and cut-out settings the usable drawdown is 25 percent of the tank volume, the replacement pump delivers 12 gallons per minute, and the pump manufacturer requires a running time of at least 1 minute per cycle. What is the drawdown, and does the tank meet the running time requirement?
• A reduced pressure principle backflow preventer is being installed in a mechanical room. What does the code require of the discharge from its relief port?
• A potable water line is being installed to fill a swimming pool. What protection does the code require on that connection?
• You measure 78 pounds per square inch of static pressure at a hose bibb early on a Sunday. The water purveyor reports that pressure in the main serving the site ranges from 42 to 80 pounds per square inch through the year. Which value governs the sizing of the water distribution system?
• A commercial storage water heater is being installed in a jurisdiction where the building code assigns seismic design requirements to the structure. What applies to that appliance?
• A frost-proof wall hydrant is being installed on an exterior wall in a freezing climate, and its barrel drains each time the hydrant is shut off. How does the code expect backflow protection to be handled on that hydrant?
• A tank-type water closet is being roughed in, and the fixture supply that runs from the branch to the closet stop is being sized. Under the IPC table of minimum fixture supply pipe sizes, what is the smallest nominal size permitted for that supply?
• A storage water heater is being installed and the crew is checking the tank fittings before piping it. What does the plumbing code require so the tank can be emptied when it is serviced?
• A barometric loop is shown on a set of drawings as the means of protecting a potable water connection. Under the IPC, what height must that loop reach and what condition does it guard against?
• The code calls for a full-open valve at certain points in the water distribution system. Which valve style satisfies that requirement, and why does it qualify?
• A tenant fit-out is being priced and the hot water branch has to be routed to every fixture that requires it. Under the IPC, which of the following fixtures must be supplied with hot or tempered water?
• Self-closing metering faucets are being specified for the lavatories in a public restroom. Under the IPC limits on maximum water consumption for fixture fittings, how much water is one of those faucets permitted to deliver?
• A cold water branch is being sized and the measured pipe run is 118 feet. That run contains six 90-degree elbows, two gate valves and one tee where the flow turns into the branch. Take these equivalent lengths as given data: each elbow counts as 4 feet, each gate valve counts as 1 foot, and the branch tee counts as 8 feet. What total developed length do you carry into the sizing table?
• Static pressure at the water meter reads 74 pounds per square inch. The most remote fixture outlet sits 32 feet above the meter and requires 20 pounds per square inch of flowing pressure. Take these values as given: the meter drops 6 pounds per square inch at design flow, the backflow assembly drops 9 pounds per square inch, and elevation costs 0.433 pound per square inch for every foot of rise. How much pressure remains to cover friction loss in the pipe and fittings?
• A tempering valve blends stored water at 140 degrees F with cold water at 55 degrees F to deliver water at 120 degrees F. For every 10 gallons the valve delivers at the blended temperature, how many gallons come from the hot side?
• A booster pump must add 46 pounds per square inch to the water pressure entering a building, and the manufacturer's pump curve is published in feet of total head. Take 2.31 feet of head per pound per square inch as given data. What head must that pump produce?
• A potable water line will supply makeup to an open cooling tower whose circulating water is dosed with biocide and a scale inhibitor. Under the IPC, what protects the potable water system at that connection?
• Public lavatories in a new office building are served from a hot water system stored well above 140 degrees F. Under the plumbing code, what has to be provided so those lavatories deliver tempered water to the user?
• You are sizing the water distribution system for a mid-size commercial building and the plan reviewer asks what method you used. Which statement describes what the plumbing code will accept?
• Laboratory faucets in a school are fitted with serrated outlets so rubber tubing can be slipped over them, and the sinks are deep enough that a tubing end can lie in standing water. Under the IPC, what protects the potable water supply at those outlets?
• A building has a reclaimed water system that flushes its water closets, and the potable system will supply makeup to the reclaimed storage tank whenever the reclaimed supply runs short. Under the plumbing code, how must that makeup connection be made?
• A kitchen sink faucet is being submitted for a commercial break room. Under the IPC limits on maximum flow rate for fixture fittings, which statement correctly pairs the limit with the pressure at which it is measured?
• The highest fixture outlet on a proposed fourth floor needs 25 pounds per square inch while flowing, and it sits 42 feet above the meter. Take these figures as given for the design flow: friction in the pipe and fittings accounts for 11 pounds per square inch, the meter accounts for 5, and each foot of rise costs 0.433. What static pressure must the meter see for that outlet to work?
• An underground lawn irrigation system protected by a pressure vacuum breaker is being modified so that liquid fertilizer is injected into the irrigation piping downstream of the point of connection. Under the IPC, what does that change require at the potable connection?
• Potable water is going to be heated indirectly by a heat transfer fluid circulating through a heat exchanger. Under the plumbing code, what governs that heat exchanger when the transfer fluid is anything other than potable water?
• A thermal expansion tank is being added to a building whose water service now carries a check device, making the piping a closed system. Where does that expansion tank belong?
• A single appliance will supply both the domestic hot water and the space heating water for a small building, with the same water circulating through the heating coils and the fixtures. Under the plumbing code, what governs that arrangement?
• An emergency shower and eyewash unit is being piped in an industrial building. What does the plumbing code require of the water supply serving that emergency equipment?
• A cold water branch carries 27 water supply fixture units. Take these capacities as given for the pressure range and developed length of this run: 3/4-inch pipe carries 14 units, 1-inch pipe carries 25 units, 1-1/4-inch pipe carries 44 units and 1-1/2-inch pipe carries 68 units. What is the smallest of those sizes that will serve the branch?
• Eight identical hotel guest bathrooms are served from one branch. Each contains one flush tank water closet, one lavatory and one bathtub with shower. Take these load values as given data: a flush tank water closet is 2.2 units where the fixture is private and 5 units where it is public; a lavatory is 0.7 private and 2 public; a bathtub with shower is 1.4 private and 4 public. Fixtures in the guest rooms of a hotel are classified as private use. What total load does the branch carry?
• A cold water branch must deliver 38 gallons per minute, and the pressure budget for that run allows a friction loss of 2.6 pounds per square inch per 100 feet of pipe. The tables available give capacity at two friction rates. At 2 pounds per square inch per 100 feet, 1-1/4-inch pipe carries 26 gallons per minute, 1-1/2-inch carries 42 and 2-inch carries 88. At 4 pounds per square inch per 100 feet, 1-1/4-inch pipe carries 38 gallons per minute and 1-1/2-inch carries 60. Which is the smallest size that stays inside the pressure budget?
• A water service must carry 30 water supply fixture units, and its total developed length measures 160 feet. The sizing table is published in rows of total developed length with no row between the ones given. Take these capacities as given data: 1-inch pipe carries 38 units in the 100-foot row, 32 units in the 150-foot row and 27 units in the 200-foot row, while 1-1/4-inch pipe carries 55 units in the 200-foot row. What size is required?
• The water sizing table is entered with total developed length. On this job the meter sits 25 feet outside the building, the run from the meter to the base of the riser measures 60 feet, the riser rises 42 feet, and the piping from the top of the riser to the most remote fixture outlet measures 18 feet. A separate 9-foot branch off the first floor main serves a janitor sink. What developed length is used?
• Take these load values as given data: a bathroom group containing a flush tank water closet counts as 3.6 water supply fixture units when the whole group is present, while the same fixtures counted one at a time are a water closet at 2.2 units, a lavatory at 0.7 units and a bathtub at 1.4 units. A dwelling contains one complete bathroom group of that kind, plus a kitchen sink at 1.4 units and a clothes washer at 1.4 units. What total load is carried into the demand conversion?
• A cold water riser serves six floors and picks up 16 water supply fixture units at each floor, with the top floor counted as the sixth. Take these capacities as given data: 1-inch pipe carries 32 units, 1-1/4-inch pipe carries 60 units and 1-1/2-inch pipe carries 96 units. Working from the top down, in which section does the riser first have to increase from 1 inch to 1-1/4 inch?
• An existing 1-1/4 inch cold water main is rated to carry 44 gallons per minute at the design friction rate for this building. The fixtures on it today total 62 water supply fixture units and produce a demand of 31 gallons per minute. A tenant proposes to add fixtures totaling 24 water supply fixture units. Take these conversions as given data: 24 units equals 17 gallons per minute, and 86 units equals 40 gallons per minute. What is the correct finding?
• A cold water main runs from the meter to a tee where one leg feeds the cold water fixtures and the other feeds the water heater. The building's fixtures total 96 water supply fixture units, and 88 of those units belong to fixtures supplied with both hot and cold water. Take as given the design rule that a fixture supplied with both hot and cold water is counted at three-quarters of its total value on each of the hot and cold branches. What load sizes the main between the meter and the tee?
• A building's fixtures total 240 water supply fixture units. The water closets and urinals, which account for 96 of those units, will be flushed from a reclaimed nonpotable system piped independently of the potable distribution. Take these conversions as given data: 96 units equals 42 gallons per minute, 144 units equals 56 gallons per minute, and 240 units equals 78 gallons per minute. What demand sizes the potable water service?
• A water service must carry 30 water supply fixture units, and the street pressure at the site measures 38 pounds per square inch. The service sizing table is published in three pressure ranges. Take these capacities as given data for the developed length of this run: a 1-inch service carries 21 units in the 30 to 45 pound range, 33 units in the 46 to 60 pound range and 45 units in the range above 60 pounds, while a 1-1/4 inch service carries 42 units in the 30 to 45 pound range. What size is required?
• A 1-1/2 inch water service is rated to carry 120 water supply fixture units at the developed length and pressure range of this site, given. A common laundry room on that service accounts for 24 water supply fixture units, and each apartment adds 12 water supply fixture units. How many apartments can the existing service carry?
• A branch serves six public flushometer valve water closets. Take as given the load value from the sizing table, which assigns a public flushometer valve water closet 10 water supply fixture units, and the fact that the table assigns that value by fixture type without reference to the volume of a single flush. The existing valves consume 1.6 gallons per flush and the replacements consume 1.28 gallons per flush. What load must the branch be sized for after the change?
• A pressure-reducing valve serves the upper zone of a building. A gauge on its outlet reads 60 pounds per square inch with nothing flowing, and the manufacturer publishes a fall-off of 12 pounds per square inch for that valve at the design flow of this zone, meaning the outlet pressure sags by that amount while water is moving. The most remote outlet in the zone sits 18 feet above the valve and friction in the piping and fittings accounts for 9 pounds per square inch at that flow. Using 0.433 pound per square inch per foot of rise, given, what flowing pressure reaches that outlet?
• A 1-inch branch has a total developed length of 310 feet once fitting allowances are included. At the design flow, the friction chart for that size shows a loss of 3.5 pounds per square inch for every 100 feet of pipe, given. The pressure budget leaves 9 pounds per square inch to be spent on friction in this run. What does the check show?
• A gauge on the second floor of an apartment building reads 58 pounds per square inch with no water flowing. The floors are 11 feet apart, and the cold water riser runs straight from the second floor to the seventh with no valve, regulator or pump between them. Using 0.433 pound per square inch per foot, given, what will a gauge on the seventh floor read with no water flowing?

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