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Sanitary Drainage — Plumber Practice Questions

87 questions · 18% of the Plumber exam

Worked questions

1. A horizontal drain pipe collects the discharge from two lavatories, a bathtub and a water closet and carries it over to the soil stack. What is the correct name for that pipe?

  • A horizontal branch drain
  • BA fixture drain

    A fixture drain covers only the run from a single trap to the first junction with other drainage. Once two fixtures combine, the pipe downstream is no longer a fixture drain.

  • CThe building drain

    The building drain is the lowest horizontal piping that receives everything in the structure. A branch on an upper floor is well upstream of it.

  • DA stack offset

    An offset describes a stack that jogs sideways and returns to vertical. It is not a pipe that fixtures connect into on a floor.

Why A is correct

Piping that runs horizontally and gathers fixture discharges on its way to a stack or the building drain is a horizontal branch. The name carries its own sizing table and its own fixture unit limits, separate from stacks.

What this question is testing

Checks precise use of drainage terminology, specifically the boundary between a fixture drain and a horizontal branch, which is where most terminology errors happen on plan review.

On the job

The naming controls which column of the sizing table you read. Horizontal branches and stacks share a table but have separate columns and separate limits, and the building drain uses a table that also depends on slope. Say the wrong name on a plan review and the reviewer will size the run from the wrong column, which usually means you get asked for a bigger pipe than the job needs.

Memory technique

One trap makes a fixture drain, two make a branch.

Exam tip

A fixture drain stops at the first junction with any other drain pipe. After that it is a branch.

Where to look it up

IPC Chapter 2 definitions, plus the horizontal branch and stack sizing table in Chapter 7. UPC uses the same concepts with its own tables.

2. Plumbing fixtures are being installed on a level that lies below the elevation of the public sewer serving the building. How must the discharge from those fixtures reach the drainage system?

  • ABy gravity, provided a backwater valve is installed on the branch serving them

    A backwater valve stops flow coming back toward the building. It provides no lift and does nothing for a fixture whose drain outlet is below the sewer.

  • BBy gravity, provided the branch serving them is increased one nominal pipe size

    Pipe size affects capacity, not elevation. A larger pipe on a negative grade still will not carry waste upward.

  • CBy gravity into the building drain, provided each fixture is separately trapped and vented

    Traps and vents protect against sewer gas and pressure changes. They are required in any case and have no bearing on whether gravity flow is possible.

  • It must drain into a sump and be lifted into the gravity drainage system by an approved pump or ejector

Why D is correct

Fixtures below the sewer must discharge into a sump and be lifted mechanically. That is the only arrangement that moves the waste from a low elevation into a drainage system running above it.

What this question is testing

Checks that the candidate recognizes an elevation problem as distinct from a capacity or backflow problem, and knows the code answer is mechanical lifting rather than a valve or a larger pipe.

On the job

Basement bathrooms are the classic case, along with floor drains in below-grade mechanical rooms. Keep everything that can drain by gravity off the ejector, because every gallon pumped is a gallon that stops moving when the power fails. Size the pit and pump for the actual fixture load, provide an alarm, and make sure the owner understands that a below-grade bathroom depends on a machine.

Memory technique

Below the sewer means you pump it.

Exam tip

Compare fixture elevation to sewer elevation first. Everything else follows from that comparison.

Where to look it up

IPC Chapter 7, building subdrains along with sumps and ejectors. The UPC requires the same approach for fixtures below the sewer, with its own pump and pit provisions.

3. Horizontal PVC drainage piping is being suspended below a floor structure. What is the maximum spacing between hangers for that piping under the IPC?

  • A6 feet

    Six feet is a spacing associated with smaller copper tubing, not with plastic drainage pipe. At six feet a warm PVC line will belly between hangers.

  • B10 feet

    Ten feet corresponds to larger copper tubing and to vertical support intervals for some materials. It is far too long for horizontal plastic drainage.

  • 4 feet
  • D12 feet

    Twelve feet is in the range used for steel pipe, which is much stiffer. Applying a steel interval to plastic guarantees sag.

Why C is correct

Four feet is the maximum horizontal hanger spacing for PVC drainage piping. Plastic pipe is flexible and softens with warm discharge, so it needs closer support than metallic materials to hold its grade.

What this question is testing

Checks whether the candidate reads support intervals from the correct material row rather than applying one familiar figure to all piping, and understands why plastic needs closer spacing.

On the job

Sag is the enemy. A belly between hangers becomes a low spot that holds water and solids, and it shows up as a chronic slow drain that no cable will fix. On long warehouse runs, support at the required interval, use hangers wide enough not to bite into the pipe, and check grade with a level as you go rather than trusting the hangers to be equal. Warm discharge will find every weak point.

Memory technique

Plastic sags, so keep the hangers close.

Exam tip

Support spacing is a material question first and a size question second. Find the material row.

Where to look it up

IPC Chapter 3, general regulations, the hanger and support spacing table. The UPC publishes its own support table with some different intervals, so confirm in the code your state adopted.

4. The drainage and vent rough-in on a two-story building is complete and will be proved with a water test. What does the code require for that test?

  • Every part of the system is put under at least a 10-foot head of water, and the test must hold with no drop for at least 15 minutes.
  • BThe system is filled to the height of the lowest fixture opening and held for 5 minutes, which is the arrangement used when testing in sections.

    A column reaching only the lowest opening puts almost no pressure on the joints below it, and five minutes is the air test duration. Testing in sections still requires a 10-foot head above each section.

  • CThe system is filled to any convenient level and watched for leaks while it drains, since a weeping joint shows itself.

    Watching a system drain is an observation rather than a test. The code requires a head that stands without dropping, because a joint that seeps slowly will not show in the seconds water takes to pass it.

  • DThe system is filled with water and then pressurized to 50 pounds per square inch for 15 minutes, matching the water distribution system test.

    Fifty pounds is borrowed from the water distribution test, where pressure is the service condition. Drainage piping is proved by a head of water or by the code's air test and is never pressurized that way.

Why A is correct

The 10-foot head requirement and the 15-minute hold are what make the test meaningful: enough pressure to find a weeping joint, and enough time for a slow leak to show as a drop in the column.

What this question is testing

Whether the candidate knows the head and duration that define an acceptable water test, and how sectional testing satisfies it.

On the job

In practice you cap the stub-outs, plug the building drain and fill from the roof, then walk every joint while it stands. Fill slowly, because a fast fill on a tall stack can blow a test plug at the base. On tall buildings the code lets you test in sections so the lower piping is not overloaded, and that is worth doing rather than putting a hundred feet of head on the base fitting.

Memory technique

Ten feet up, fifteen minutes still.

Exam tip

Ten feet of head, fifteen minutes, no drop. That trio answers most water test questions.

Where to look it up

Tests and inspections are in IPC Section 312. UPC prescribes its own test heads, durations and permitted methods, and some jurisdictions restrict air testing on plastic piping, so follow the adopted code.

5. An 8-inch building sewer will run 300 feet from the building to its point of connection. Take these values as given: the minimum slope permitted for pipe 8 inches and larger is 1/16 inch per foot, and the survey shows 16 inches of available fall between the two inverts. Does the run work at the minimum slope?

  • AYes; at the minimum slope the run needs only about 1.6 inches of fall.

    This confuses inches with feet in the result. Three hundred feet at a sixteenth of an inch per foot is 18.75 inches, not 1.6.

  • BYes; the run needs 18.75 inches of fall, and the 16 inches available is within the tolerance allowed on large sewers.

    There is no tolerance that lets a sewer be built below the minimum slope. Falling short means redesigning the run.

  • No; at the minimum slope the run needs 18.75 inches of fall, which is more than the 16 inches available.
  • DNo; the run needs 75 inches of fall, because 1/4 inch per foot applies to every building sewer.

    The quarter inch per foot minimum applies to small pipe. Larger diameters are permitted flatter, which is why 8 inch is in the 1/16 inch per foot row.

Why C is correct

Multiplying the minimum slope by the developed length gives the fall the run must have. Comparing that with the surveyed drop answers the question directly, and here the requirement exceeds what the site provides.

What this question is testing

Whether the candidate can convert a minimum slope and a length into required fall and compare it against site conditions in consistent units.

On the job

Long sewers on flat sites live or die on this arithmetic, and it should be done before anyone digs. When the numbers do not close, the options are a deeper tap if the authority allows it, a shorter alignment, or a lift station. Verify the manhole invert yourself rather than trusting a record drawing, because a few inches of error changes the answer.

Memory technique

Length times slope equals the drop you must have.

Exam tip

Fall in inches equals length in feet times the slope in inches per foot. Keep the units straight.

Where to look it up

Minimum slopes by pipe size are in IPC Section 704 and its slope table. UPC sets different minimum slopes, and flatter slopes on large pipe generally require specific approval, so confirm under the adopted code.

6. A sewage ejector will discharge through a 2-inch pipe. Take these values as given: the discharge piping must maintain a velocity of at least 2 feet per second, the inside cross-sectional area of the 2-inch pipe is 0.0233 square foot, and 1 cubic foot per second equals 448.8 gallons per minute. What is the smallest pump capacity that satisfies the velocity requirement?

  • A10.5 gallons per minute

    That result comes from converting the area straight to gallons per minute without multiplying by velocity. Area alone is not a flow.

  • 20.9 gallons per minute
  • C31.4 gallons per minute

    That result uses 3 feet per second. Some references quote higher scouring velocities for other applications, but the value to use is the one the problem supplies.

  • D41.8 gallons per minute

    That result uses 4 feet per second, doubling the required velocity. Oversizing this way produces a pump that short cycles and hammers the check valve.

Why B is correct

Velocity is what keeps solids suspended in a pressurized discharge line. Multiplying the pipe's area by the required velocity gives the flow in cubic feet per second, and the conversion factor turns that into the gallons per minute a pump is rated in.

What this question is testing

Whether the candidate can convert between velocity, pipe area and pump capacity, keeping cubic feet per second and gallons per minute straight.

On the job

Ejector selection usually starts with the head the pump must overcome and stops there, which is how undersized discharge flows happen. Running the velocity check tells you whether the pipe and pump are a matched pair, and it explains the classic complaint of a two-year-old ejector line that plugs solid: a big pipe with a small pump moves water slowly enough for everything else to settle out. Bigger discharge pipe is not automatically better.

Memory technique

Area times velocity, then four hundred forty-nine to get gallons per minute.

Exam tip

Flow equals area times velocity. Get to cubic feet per second first, then convert once at the end.

Where to look it up

IPC Chapter 7, the sumps and ejectors provisions covering discharge piping. The UPC states its own minimum velocity and pump capacity requirements for sewage ejectors, so verify in your adopted code.

7. The building drain leaves the foundation with its invert at elevation 100.60 feet. The invert of the public sewer at the point of connection is at elevation 96.85 feet, and the building sewer will run 340 feet of developed length between those two points. Take the minimum slope for the 6-inch pipe being used as 1/8 inch per foot, given. What grade is available, and does it work?

  • AAbout 0.011 inch per foot, far below the minimum, so the sewer has to be pumped

    This divides feet of fall by feet of run and then reports the answer as inches per foot. The result, 0.011, is the grade in feet per foot; multiplying by 12 converts it to the 0.13 inch per foot the question asks for.

  • BAbout 3.75 inches per foot, well above the minimum, so gravity drainage works easily

    This treats the 3.75 foot elevation difference as though it were the slope itself. A grade of nearly four inches per foot would be a stair, not a sewer.

  • CAbout 0.13 inch per foot, which falls short of the minimum, so the sewer has to be pumped

    The arithmetic here is right but the comparison is wrong. One eighth of an inch is 0.125, and 0.13 is larger than 0.125, so the available grade clears the minimum rather than falling short of it.

  • About 0.13 inch per foot, which meets the minimum, so gravity drainage works

Why D is correct

Fall is 100.60 minus 96.85, or 3.75 feet, which converts to 45 inches. Divided by 340 feet that is about 0.13 inch per foot, just above the 0.125 inch per foot the minimum works out to, so the line drains by gravity. The margin is two and a half inches over the whole run, which means the grade has to be held carefully during installation.

What this question is testing

This checks whether you can convert an elevation difference into a grade in inches per foot without a unit slip, and whether you can compare a decimal grade against a fractional minimum correctly.

On the job

This is the calculation that decides whether a building gets a gravity sewer or an ejector package, and it is worth doing before the foundation elevation is set rather than after. When the margin is this thin, the things that eat it are real: a deeper tie-in than the utility drawing showed, an unexpected rock ledge, or a crew that lays the first hundred feet a little rich and runs out of fall at the end.

Memory technique

Feet of fall times twelve, divided by feet of run, equals inches per foot.

Exam tip

Convert the fall to inches before dividing, and turn the fractional minimum into a decimal before comparing.

Where to look it up

Minimum slope by pipe size is in IPC 704.1; building sewer requirements are in IPC Chapter 7. UPC sets its own minimum slopes and applies them to different size breaks than the IPC does, so check the figure against the code your state has adopted.

80 more in the bank

Answers and explanations for these are in the app.

  • Gravity drainage leaving a building carries one name inside and a different name outside. At what point does the building drain end and the building sewer begin?
  • Stack sizing tables limit both the total load on a stack and the load connected within a branch interval. What does the term branch interval describe?
  • A 4-inch horizontal sanitary drainage pipe is being installed under a slab. Under the IPC, what is the minimum slope this pipe may be laid at?
  • A horizontal drain has been installed at a grade far steeper than the code minimum. Why does an excessively steep horizontal drain cause trouble in service?
  • A horizontal drain branch runs 46 feet from the last fixture connection to the stack, and it is to be installed at a slope of 1/4 inch per foot. How much total fall does that run require from one end to the other?
  • A building sewer can drop a total of 18 inches between the point where it leaves the building and the point where it must tie into the main. If the pipe is laid at 1/8 inch per foot, what is the longest run this available fall will support?
  • A soil stack serves six floors of a building. The horizontal branches on each floor connect a total of 32 fixture units to the stack, and the loading is identical on every floor. What total drainage fixture unit load must the base of the stack be sized to carry?
  • A building drain must carry a total of 205 drainage fixture units, and the site allows it to be installed at a slope of 1/4 inch per foot. Use the following capacities given for this problem: a 3-inch drain at 1/4 inch per foot carries 42 fixture units, a 4-inch drain at 1/8 inch per foot carries 180 fixture units, a 4-inch drain at 1/4 inch per foot carries 216 fixture units, and a 5-inch drain at 1/8 inch per foot carries 390 fixture units. What is the smallest drain that will serve?
  • For this problem, take these values as given: the horizontal branch under consideration is limited to 20 drainage fixture units, and each private bathroom group is counted as 6 drainage fixture units. Considering only these fixture unit values and ignoring any separate limit on the number of water closets, how many bathroom groups may connect to that branch?
  • Sizing tables for drainage piping are entered with a total number of drainage fixture units. What does a single drainage fixture unit actually represent?
  • A long horizontal drainage line is being installed with no changes in direction along its length. What is the maximum spacing the code allows between cleanouts on that run?
  • A cleanout must be installed so that drain cleaning equipment can actually be worked through it. Under the IPC, what clearance is required in front of a cleanout?
  • Besides the maximum spacing rule, the code requires cleanouts wherever a horizontal drainage line turns sharply enough to obstruct cleaning equipment. Under the IPC, which change of direction triggers a required cleanout?
  • Cleanout openings must be large enough to admit the equipment used to clear the pipe they serve. How does the code establish the required size of a cleanout?
  • A cleanout is required at the base of each soil or waste stack. Which arrangement satisfies that requirement where the base of the stack will be concealed inside a finished chase?
  • A horizontal fixture branch changes direction to enter a vertical drainage stack. Which fitting is approved for making that horizontal to vertical change of direction?
  • At the bottom of a soil stack the flow must turn from vertical to horizontal. Which fitting is approved for making that change of direction?
  • Two horizontal drainage lines are being joined together so that both continue in the same horizontal run. Which fitting is appropriate for that horizontal to horizontal connection?
  • Back-to-back water closets are proposed on a single vertical drain using a double sanitary tee. Under the IPC, what condition must be met for that arrangement to be acceptable?
  • A new fixture must be connected to an existing cast iron drainage line already buried under a slab. Which method of making that connection is prohibited by the code?
  • A drainage stack must jog around an obstruction using an offset that is less than 45 degrees from vertical. How does the code require that offset to be sized?
  • A drainage stack must be offset at an angle of 45 degrees or more from vertical to follow a building setback. How does the code treat the horizontal portion of that offset?
  • A sump pit is being installed to receive the discharge of fixtures located below the sewer. What construction does the code require for that pit?
  • Discharge piping is being run from a sewage pump in a sealed sump up to the gravity drainage system. What does the code require in that discharge line?
  • A backwater valve protects fixtures from sewage flowing back into the building when the public sewer surcharges. Under what condition does the code require one?
  • A building sewer is being installed in a trench that has been cut partly through rock. How does the code require that piping to be bedded and backfilled?
  • A 3-inch soil stack standing 34 feet tall must be filled completely with water for the drainage and vent water test. For this problem, use the given value that 3-inch pipe holds 0.37 gallon per foot. About how much water is needed to fill that stack?
  • A horizontal drainage line is being laid out, and the designer proposes reducing the pipe size downstream of the last fixture connection because the remaining load is small. What does the code say about that?
  • A sink is fitted with a 2-inch trap. What is the minimum size of the fixture drain that carries the discharge away from that trap?
  • A riser diagram labels one vertical drainage line as a soil stack and another as a waste stack. What distinguishes the two under the code definitions?
  • A single water closet will discharge into a new horizontal branch. Take these values as given: the water closet is rated at 4 drainage fixture units, a 2-inch horizontal branch is permitted to carry 6 drainage fixture units, and the code sets a minimum of 3 inches for any drain that receives the discharge of a water closet. What size branch is required?
  • A cleanout is being installed on a horizontal drainage line. How does the code require the fitting to be oriented relative to the flow in that line?
  • A required cleanout would fall in the middle of a newly tiled floor, and a floor-mounted water closet sits on the drainage line a few feet away. What does the code accept in that situation?
  • A building sewer serving a large facility is 8 inches in diameter and runs underground for a long distance. How does the code provide for access on a sewer that size?
  • A cleanout on an underground drainage line falls beneath a basement slab that will be finished out. How must that cleanout be handled?
  • A floor cleanout in a mechanical room is the nearest opening to a new piece of equipment, and the crew proposes running the equipment drain into it. What does the code say about that connection?
  • A long horizontal drainage branch runs from its farthest fixture connection to the stack. Beyond the spacing rule and the rule for changes of direction, where else does the code require a cleanout on that line?
  • A horizontal branch serves two complete bathroom groups on the same floor, each made up of a water closet, a lavatory and a bathtub with a shower head. Take these values as given: a bathroom group of that composition is counted as 6 drainage fixture units, while the fixtures counted individually would be 4 for the water closet, 1 for the lavatory and 2 for the bathtub. What total load does the branch carry?
  • A 3-inch soil stack is fed by fixtures connecting at three branch intervals, which contribute 12, 10 and 9 drainage fixture units respectively. Take these table values as given: a 3-inch stack with three branch intervals or fewer may carry 30 drainage fixture units in total, a 3-inch stack with more than three branch intervals may carry 48 drainage fixture units in total, and no more than 20 drainage fixture units may connect within any one branch interval. Is the 3-inch stack adequate?
  • A building drain must be trenched alongside an existing spread footing, and the invert falls below the bottom of that footing. What does the code require of the excavation?
  • A section of buried cast-iron building drain is being cut out and replaced with PVC beneath an existing slab. How does the code permit those two materials to be joined?
  • Indirect waste piping discharges into a waste receptor. What distinguishes an air gap from an air break at that termination?
  • A commercial dishwashing machine and an ice maker are being connected in a restaurant kitchen. How does the code require their waste to reach the drainage system?
  • A sterilizer in a hospital central supply department must discharge to the drainage system. How does the code require that connection to be made?
  • A water softener in a mechanical room has to discharge its backwash and regeneration flow. How does the code require that discharge to reach the drainage system?
  • An existing 3-inch horizontal branch is permitted to carry 20 drainage fixture units and today serves fixtures totaling 14 drainage fixture units. Take these values as given: a lavatory counts as 1, a kitchen sink as 2, a floor drain as 2 and a water closet as 4 drainage fixture units. Which addition fits without enlarging the branch?
  • A building drain leaves a building at 4 inches carrying 160 drainage fixture units. Out on the lot, the building sewer picks up another 40 drainage fixture units from a detached accessory structure before reaching the public sewer. Take these values as given at the slope being used: a 4-inch pipe carries 180 drainage fixture units, a 5-inch pipe carries 390 drainage fixture units, and drainage piping may not be reduced in the direction of flow. What size is required downstream of that junction?
  • A building has a restroom on a level below the public sewer and additional fixtures on the floors above it. How does the code require those two drainage loads to be handled?
  • A sump pit is 24 inches in diameter, and the floats are set so that 18 inches of depth lies between the pump-off level and the pump-on level. Take these values as given: 1 cubic foot holds 7.48 gallons, and the peak inflow to the pit is 20 gallons per minute. What volume is stored between the two float levels, and how long does that peak inflow take to fill it?
  • The disposer going in at a pot wash station is a commercial food waste grinder rather than a residential unit. How must its waste be piped under the code?
  • A horizontal branch will receive fixtures totaling 24 drainage fixture units plus the discharge of a pump running continuously at 15 gallons per minute. Take these values as given: continuous flow is converted at 2 drainage fixture units for each gallon per minute, a 3-inch branch carries 20 drainage fixture units, and a 4-inch branch carries 160 drainage fixture units at the slope being used. What size branch is required?
  • A building drain must carry 210 drainage fixture units, and the site allows no more than 1/8 inch per foot of fall. Take these table values as given: at 1/4 inch per foot a 4-inch drain carries 216 drainage fixture units and a 5-inch drain carries 480; at 1/8 inch per foot a 4-inch drain carries 180 drainage fixture units and a 5-inch drain carries 390. What size building drain is required?
  • You are sizing gravity drainage with the code open in front of you. How are the sizing tables organized between horizontal branches and stacks on one hand and building drains and building sewers on the other?
  • A drainage stack must jog around structure at a point above the highest fixture branch connected to it. How does the code treat that offset?
  • A perimeter subsoil drain around a basement foundation collects groundwater. Where does the code permit that water to be discharged?
  • A designer proposes to size a large sanitary drainage system by a computer-based engineering method instead of the fixture unit tables. What does the code require for that approach?
  • A flat roof is enclosed by a parapet on all four sides and is drained by interior roof drains. Under the plumbing code, what has to be provided in case those primary drains become blocked?
  • A roof area of 4,800 square feet drains to a single roof drain, and the design rainfall rate for the location is 4 inches per hour. Take this relationship as given data: flow in gallons per minute equals the roof area in square feet multiplied by the rainfall rate in inches per hour multiplied by 0.0104. What flow must that drain and its conductor carry?
  • The filter backwash line and the drain-down line for a swimming pool are being connected to the building's drainage system. How does the plumbing code require those lines to be connected?
  • A PVC building drain under a slab was laid across uneven fill, and a camera inspection shows water standing at two low points even though the invert at the far end is lower than the invert at the stack. What does the plumbing code require of that installation?
  • An apartment contains a bathroom group, a clothes washer, a separate lavatory in a hall bath, and a kitchen with a two-compartment sink that receives both a food waste grinder and the dishwasher through the sink's single trap. Take these values as given: bathroom group 6 drainage fixture units, clothes washer 3, lavatory 1, kitchen sink 2, dishwasher 2, and a combination of fixtures discharging through one trap is counted once at the value of the largest fixture in the combination. What is the total drainage fixture unit load?
  • A building drain serves plumbing fixtures totaling 172 drainage fixture units. A water treatment system also backwashes into that same drain at a steady 15 gallons per minute. Take these values as given: steady flow converts at 2 drainage fixture units for each gallon per minute, and at a slope of 1/8 inch per foot a 4-inch drain is limited to 180 drainage fixture units while a 5-inch drain is limited to 390. What size building drain is required?
  • A floor sink will receive the indirect waste from a walk-in cooler and an ice machine in a commercial kitchen. What does the plumbing code require of that receptor and of the waste pipes discharging into it?
  • A drainage stack carries a total fixture unit load that the sizing table allows on a 3-inch stack. One floor, however, connects a 4-inch horizontal branch serving a battery of water closets. What size must the stack be?
  • An indirect waste pipe from a commercial ice machine terminates over a floor sink. Under the plumbing code, how is the required air gap at that termination determined and measured?
  • A soil stack comes down through a building and, below the lowest horizontal branch connected to it, offsets horizontally for 14 feet before turning back down and running to the building drain. How is that horizontal offset portion sized?
  • Roof drains are being installed on a flat roof that serves no purpose other than weather protection. What does the plumbing code require at each drain opening?
  • A horizontal branch will serve three floor-mounted water closets in a commercial restroom. Take these values as given: each water closet is 6 drainage fixture units, a 3-inch horizontal branch is limited to 20 drainage fixture units, a 4-inch horizontal branch is limited to 160 drainage fixture units, and no more than two water closets may discharge into a 3-inch horizontal branch. What is the minimum size for that branch?
  • A sizing table gives the maximum roof area a vertical conductor may serve at a rainfall rate of 4 inches per hour: a 3-inch conductor serves 2,320 square feet and a 4-inch conductor serves 4,980 square feet. The local design rainfall rate is 6 inches per hour, and 2,000 square feet of roof drains to one conductor. What size conductor is required?
  • A remodel adds a lavatory to a bathroom whose only nearby waste is an existing 1-1/2 inch branch. Take these values as given: a 1-1/2 inch horizontal branch is limited to 3 drainage fixture units, the branch already serves a bathtub at 2 units and a lavatory at 1 unit, and the new lavatory adds 1 unit. What does the code require before that fixture may be connected?
  • The plumbing code sets a minimum slope for horizontal sanitary drainage piping. What is that minimum slope intended to produce in the pipe?
  • A floor drain is installed in a mechanical room only to handle an accidental spill or an equipment leak, and no fixture or piece of equipment discharges into it during normal operation. How does that drain enter the drainage fixture unit total for the system?
  • You are sizing a horizontal storm drain with the code open in front of you. Besides the roof area being served, what two pieces of information must you have before the horizontal storm drainage table can be read?
  • An existing 4-inch soil stack serves five floors, each connecting 38 drainage fixture units, and a sixth identical floor is proposed. Take these limits as given: a 4-inch stack is limited to 500 drainage fixture units in total and to 90 drainage fixture units within any one branch interval. Does the existing stack accept the added floor?
  • A sewage sump receives a steady inflow of 20 gallons per minute. The pit holds 15 gallons between the pump-on and pump-off float settings, and the pump is rated at 45 gallons per minute at the system head. How long does the pump run during each cycle?
  • A site drawing shows an 8-inch building sewer to be installed at a grade of 0.5 percent. Take these values as given: a grade of 1 percent equals 0.12 inch per foot, and the code minimum slope for 8-inch drainage piping is 1/16 inch per foot. What is the grade in inches per foot, and does it satisfy the minimum?
  • Identical fixtures are installed twice: once in a dwelling unit and once in an office restroom open to the public. The set is one water closet, one lavatory and one shower. Take these values as given: private use water closet 3, lavatory 1, shower 2; public use water closet 4, lavatory 2, shower 2. How do the two totals compare?
  • A building sewer leaves the foundation with its invert 4.0 feet below finished grade and runs toward the street at 1/8 inch per foot. Grade is level across the run. At a point 72 feet from the building the sewer passes beneath a water service whose underside sits 3.5 feet below finished grade. The project requires the sewer to be at least 12 inches below the water service where the two cross. What is the vertical separation at the crossing?
  • A building drain must fall a total of 16 inches over 88 feet of developed length, from the last fixture connection to the point where it leaves the foundation. The first 48 feet passes over footings and can be run at no more than 1/8 inch per foot. What uniform slope must the remaining 40 feet be run at so the drain arrives at the required elevation?
  • A civil drawing calls out the building sewer at a grade of 1 in 50, meaning one foot of fall for every 50 feet of run. Take the code minimum slope for the 4-inch pipe being installed as 1/4 inch per foot, given. What is that grade in inches per foot, and how does it compare with the minimum?

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