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OH Journeyman Plumber practice questions

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Question 1Plumbing Systems and Fixtures

Under the Ohio Plumbing Code, what is the minimum required diameter of a building drain serving a single-family dwelling?

  1. 2 inches
  2. 1 1/2 inches
  3. 3 inches Correct answer.
  4. 4 inches

Explanation

The Ohio Plumbing Code requires a building drain serving a single dwelling to be not less than 3 inches in diameter, matching the minimum building sewer size. Smaller sizes such as 1 1/2 or 2 inches are permitted only for individual branch lines and fixtures, not the main building drain.

Question 2Plumbing Systems and Fixtures

What is the maximum developed length of a 1 1/2 inch trap arm from the trap weir to the vent fitting?

  1. 6 feet
  2. 5 feet Correct answer.
  3. 3 feet
  4. 8 feet

Explanation

A trap arm must not exceed the developed length equal to its diameter in inches times the slope allowance, which for a 1 1/2 inch trap arm yields a maximum of 5 feet. The limit prevents the trap from self-siphoning before the vent is reached.

Question 3Plumbing Systems and Fixtures

A water closet is installed in a room. What is the minimum required clearance from the centerline of the closet to any side wall?

  1. 12 inches
  2. 18 inches
  3. 15 inches Correct answer.
  4. 20 inches

Explanation

The code requires at least 15 inches of clear space from the centerline of a water closet to any side wall or partition. This allows a person to use the fixture with adequate shoulder and elbow room.

Question 4Plumbing Systems and Fixtures

Which material is approved for use as an underground building sewer where the effluent is conveyed by gravity?

  1. ABS DWV
  2. Schedule 40 PVC DWV
  3. Cast iron soil pipe
  4. All of these are commonly approved Correct answer.

Explanation

The code lists several approved materials for building sewers, including PVC DWV, ABS DWV, and cast iron soil pipe, provided joints and installation meet the listed standards. Selection among them depends on local conditions, loading, and adopted standards rather than a single mandated material.

Question 5Plumbing Systems and Fixtures

What is the minimum size of a vent stack serving a water closet branch in a dwelling?

  1. 1 1/2 inches
  2. 3 inches
  3. 1 1/4 inches Correct answer.
  4. 2 inches

Explanation

A vent stack must be sized according to the fixture units served, and the minimum size permitted for any vent is 1 1/4 inches. A water closet branch vented in accordance with the tables is commonly served by a 1 1/2 inch vent, but the floor minimum is 1 1/4 inches.

Question 6Plumbing Systems and Fixtures

A lavatory drain is connected to a horizontal branch. What device must be installed to prevent sewer gas from entering the building?

  1. A trap primer
  2. A cleanout
  3. A backwater valve
  4. A fixture trap Correct answer.

Explanation

Every fixture connected to the drainage system must be protected by a water-seal trap that prevents sewer gas from passing into the building. Trap primers, cleanouts, and backwater valves serve other purposes and do not provide the required water seal.

Question 7Plumbing Systems and Fixtures

What is the minimum air gap required for a fixture with an effective open diameter of 1 inch?

  1. 1/2 inch
  2. 2 inches Correct answer.
  3. 1 inch
  4. 1 1/2 inches

Explanation

An air gap must be at least twice the effective open diameter of the fixture outlet, with a minimum of 1 inch. For a 1 inch effective opening, twice the diameter gives 2 inches.

Question 8Plumbing Systems and Fixtures

Which fixture unit value is typically assigned to a private residential water closet in drainage sizing tables?

  1. 4 fixture units Correct answer.
  2. 1 fixture unit
  3. 6 fixture units
  4. 2 fixture units

Explanation

A private water closet is commonly rated at 4 drainage fixture units in the standard tables. This value is used when adding branch and building drain loads.

Question 9Plumbing Systems and Fixtures

A 3 inch horizontal drain carries a branch connection. What is the minimum slope required for a 3 inch horizontal drain?

  1. 1/4 inch per foot
  2. 1/2 inch per foot
  3. 1/16 inch per foot
  4. 1/8 inch per foot Correct answer.

Explanation

Horizontal drains 3 inches and larger may be installed at a slope of not less than 1/8 inch per foot, while smaller drains require 1/4 inch per foot. The reduced slope for larger pipe still provides adequate scouring velocity.

Question 10Plumbing Systems and Fixtures

A building has a 4 inch building drain. What is the minimum size of the building sewer serving it?

  1. 6 inches
  2. 4 inches Correct answer.
  3. 2 inches
  4. 3 inches

Explanation

The building sewer must be at least the diameter of the building drain it serves, so a 4 inch building drain requires a building sewer of not less than 4 inches. Smaller sewer sizes are not permitted to carry the same load.

Question 11Plumbing Systems and Fixtures

A horizontal wet vent is used to vent a bathroom group. Which condition must be met for the wet vent to be acceptable?

  1. The wet vent may be smaller than the drain it serves
  2. The wet vent must be at least 2 inches and carry only the fixtures it vents Correct answer.
  3. The wet vent may connect to a soil stack above the highest fixture
  4. The wet vent may serve fixtures on more than one floor

Explanation

A horizontal wet vent must be sized and arranged so it carries only the fixtures it vents, typically at least 2 inches for a bathroom group, and it must not serve fixtures on other floors. These limits keep the vent from being overwhelmed by drainage flow.

Question 12Plumbing Systems and Fixtures

What is the minimum trap seal depth required for a fixture trap?

  1. 2 inches Correct answer.
  2. 4 inches
  3. 1 inch
  4. 3 inches

Explanation

A liquid trap seal must be at least 2 inches deep and no more than 4 inches deep. The minimum ensures an adequate barrier against sewer gas, while the maximum limits the volume of trapped water.

Question 13Plumbing Systems and Fixtures

A water heater relief valve discharge pipe terminates in a location where it could be plugged. What is the correct installation?

  1. Run the discharge pipe to the floor drain through a trap
  2. Terminate the discharge pipe so it drains by gravity with no threaded end Correct answer.
  3. Cap the discharge pipe to prevent debris entry
  4. Reduce the discharge pipe to 1/2 inch copper

Explanation

A temperature and pressure relief valve discharge must terminate freely to drain by gravity, with no threads or fittings that could be capped or plugged, and must not be trapped. This ensures the valve can relieve pressure safely.

Question 14Plumbing Systems and Fixtures

What is the maximum distance a water closet may be located from the vent stack connection when the closet is individually vented?

  1. 3 feet
  2. 10 feet
  3. 6 feet
  4. No specific limit if the trap arm slope is maintained Correct answer.

Explanation

An individually vented water closet has no fixed distance limit to the vent; the controlling requirement is that the trap arm slope and vent connection comply with the code. The vent must connect within the trap arm length limits based on pipe size.

Question 15Plumbing Systems and Fixtures

A lavatory is installed in a counter with a backsplash. What is the minimum spacing between the fixture and the adjacent wall?

  1. 1 inch
  2. 6 inches
  3. 4 inches
  4. 2 inches Correct answer.

Explanation

Where a fixture is installed adjacent to a wall, a clearance of at least 2 inches is required between the fixture and the wall to allow cleaning and use. This applies to lavatories and similar fixtures in counter installations.

Question 16Plumbing Systems and Fixtures

A floor drain is installed in a kitchen. What is required to prevent sewer gas from entering through the drain?

  1. A trap primer only
  2. A backwater valve
  3. A cleanout above the floor
  4. A trap with a seal and a vent Correct answer.

Explanation

A floor drain must be trapped and vented so that a water seal is maintained and the trap is protected from siphonage. A trap primer may help maintain the seal but does not replace the trap and vent.

Question 17Plumbing Systems and Fixtures

What is the minimum size of a water supply pipe serving a single water closet with a flushometer valve in a public restroom?

  1. 1/2 inch
  2. 1 inch Correct answer.
  3. 3/4 inch
  4. 1 1/4 inches

Explanation

Flushometer valves require a larger supply to deliver the necessary flush volume, and a single water closet with a flushometer valve typically requires a minimum 1 inch supply. Smaller supplies may not deliver adequate pressure and volume.

Question 18Plumbing Systems and Fixtures

A horizontal branch drain receives a lavatory and a bathtub. What is the minimum size of the branch drain?

  1. 1 1/2 inches Correct answer.
  2. 2 inches
  3. 1 1/4 inches
  4. 3 inches

Explanation

A horizontal branch serving a lavatory and a bathtub is commonly sized at 1 1/2 inches, which accommodates the combined fixture units and the fixture drain sizes. Larger sizes are permitted but are not the minimum.

Question 19Plumbing Systems and Fixtures

A grease interceptor is required for a commercial kitchen. Where must the interceptor be installed?

  1. On the discharge side of the fixture drain before it enters the building drain Correct answer.
  2. Downstream of the building sewer connection
  3. At the vent stack
  4. In the water supply line to the kitchen

Explanation

A grease interceptor must be installed so kitchen waste flows through it before entering the building drainage system, allowing grease to separate and be retained. Installing it downstream of the building sewer would not protect the drainage system.

Question 20Plumbing Systems and Fixtures

A vertical drain serving a water closet on the top floor connects to a horizontal branch. What fitting is required at the base of the stack?

  1. A sanitary tee
  2. A long-turn fitting or two 45-degree fittings Correct answer.
  3. A double sanitary tee
  4. A reducing coupling

Explanation

At the base of a soil or waste stack, the change from vertical to horizontal flow must be made with a long-turn fitting or an equivalent combination of 45-degree fittings to prevent blockage and reduce turbulence. A sanitary tee is not permitted for this direction change.

Question 21Plumbing Systems and Fixtures

A building has a water service with a pressure of 80 psi at the meter. What device is required to protect the plumbing system if the pressure exceeds the limit for the fixtures?

  1. A check valve
  2. A vacuum breaker
  3. A backflow preventer
  4. A pressure-reducing valve Correct answer.

Explanation

Where the water service pressure exceeds the maximum allowed for the system, a pressure-reducing valve must be installed to bring the pressure within acceptable limits. Check valves, vacuum breakers, and backflow preventers serve other functions and do not regulate pressure.

Question 22Plumbing Systems and Fixtures

A 4 inch building drain is installed at a slope of 1/8 inch per foot. What is the minimum slope allowed for a 4 inch building drain under the code?

  1. 1/16 inch per foot
  2. 1/8 inch per foot Correct answer.
  3. 1/4 inch per foot
  4. 1/2 inch per foot

Explanation

For drains 3 inches and larger, the minimum slope is 1/8 inch per foot. A 4 inch building drain therefore may be installed at 1/8 inch per foot, though steeper slopes are permitted.

Question 23Plumbing Systems and Fixtures

A fixture drain connects to a horizontal branch and the trap arm is 4 feet long with a 1 1/2 inch trap. What is the maximum allowable length of the trap arm?

  1. 4 feet
  2. 6 feet
  3. 3 feet
  4. 5 feet Correct answer.

Explanation

The maximum developed length of a 1 1/2 inch trap arm is 5 feet. A 4 foot trap arm is therefore within the allowable length and would not require an additional vent.

Question 24Plumbing Systems and Fixtures

A horizontal wet vent serves a bathroom group on the top floor. Which condition would make the wet vent unacceptable?

  1. The wet vent is 2 inches in diameter
  2. The wet vent connects to the branch within the allowable length
  3. The wet vent carries only the fixtures it vents
  4. The wet vent serves fixtures on two different floors Correct answer.

Explanation

A horizontal wet vent may serve only fixtures on the same floor; extending it to fixtures on another floor is not permitted because drainage from upper fixtures would impair the vent. The other listed conditions are consistent with a compliant wet vent.

Question 25Plumbing Systems and Fixtures

A water closet is installed in a public restroom with a flushometer valve. What is the minimum water supply pressure required at the fixture for proper operation?

  1. 8 psi
  2. 15 psi
  3. 25 psi Correct answer.
  4. 10 psi

Explanation

Flushometer valves require a minimum flowing pressure at the fixture, commonly 25 psi for water closets, to deliver the design flush volume. Lower pressures can cause incomplete flushing and valve malfunction.

Question 26Plumbing Systems and Fixtures

A public restroom has a row of lavatories installed along one wall. What is the minimum clear wall space required between adjacent lavatory bowls?

  1. 30 inches
  2. 4 inches
  3. 18 inches
  4. 12 inches Correct answer.

Explanation

The Ohio Plumbing Code requires a minimum of 12 inches of clear space between adjacent lavatory bowls in a multiple-fixture installation. This spacing allows users to stand and use each fixture without interference. Larger dimensions like 18 or 30 inches apply to other fixtures or clearances, not to lavatory-to-lavatory spacing.

Question 27Plumbing Systems and Fixtures

A drinking fountain is installed in a commercial building. What is the maximum height above the floor for the fountain's orifice?

  1. 48 inches
  2. 36 inches
  3. 54 inches
  4. 42 inches Correct answer.

Explanation

The Ohio Plumbing Code limits the drinking fountain orifice to a maximum of 42 inches above the finished floor to keep the fixture usable for most standing adults. This height also aligns with accessibility guidance for a standard-height fountain. Heights above 42 inches are not permitted for the bubbler orifice.

Question 28Plumbing Systems and Fixtures

A commercial kitchen sink is equipped with a pre-rinse spray valve. What device must protect the potable water supply at this connection?

  1. A dual check valve
  2. An air gap or vacuum breaker Correct answer.
  3. A pressure-reducing valve
  4. A thermal expansion tank

Explanation

A pre-rinse spray valve on a commercial sink presents a cross-connection risk because the outlet can be submerged in soiled water. The code requires an air gap or an approved vacuum breaker to prevent backflow into the potable supply. Check valves alone are not acceptable for this high-hazard application.

Question 29Plumbing Systems and Fixtures

A floor-mounted water closet is installed in a public restroom. What is the minimum clearance required from the centerline of the fixture to the adjacent side wall?

  1. 18 inches
  2. 12 inches
  3. 15 inches Correct answer.
  4. 10 inches

Explanation

The code requires at least 15 inches of clear space from the centerline of a water closet to any side wall or partition. This dimension ensures adequate shoulder and elbow room for the user. The 15-inch figure applies to both sides of the fixture.

Question 30Plumbing Systems and Fixtures

A bathtub has a shower head installed above it. What is the minimum vertical distance from the shower head to the floor drain or tub rim?

  1. 66 inches
  2. 78 inches
  3. 72 inches Correct answer.
  4. 60 inches

Explanation

The Ohio Plumbing Code sets a minimum shower head height of 72 inches above the drain or tub rim. This clearance allows a standing bather to shower comfortably. Heights below 72 inches are not permitted for a shower head.

Question 31Plumbing Systems and Fixtures

A commercial dishwasher discharges into a floor sink. What is the minimum air gap required between the discharge pipe and the flood-level rim of the receptor?

  1. One-half the pipe diameter
  2. 1 inch or twice the pipe diameter, whichever is greater
  3. Twice the effective opening diameter of the indirect waste pipe Correct answer.
  4. Four times the pipe diameter

Explanation

For an indirect waste pipe, the required air gap is at least twice the effective opening diameter, measured above the receptor's flood-level rim. This indirect-waste rule does not add the separate one-inch minimum used in potable-water air-gap requirements.

Question 32Plumbing Systems and Fixtures

A horizontal drainage branch serving a lavatory is 12 feet long and receives no other fixtures. What is the maximum length permitted for the trap arm before additional venting is required?

  1. 8 feet Correct answer.
  2. 12 feet
  3. 15 feet
  4. 5 feet

Explanation

For a 1 1/4-inch or 1 1/2-inch trap arm, the code limits the developed length to 8 feet before the vent connection. The trap arm must also slope at the required rate and not exceed the fall limit. Exceeding the length would require a revent or additional vent.

Question 33Plumbing Systems and Fixtures

A water closet is installed in an alcove. What is the minimum clear width of the alcove measured at the fixture?

  1. 24 inches
  2. 36 inches
  3. 30 inches Correct answer.
  4. 42 inches

Explanation

An alcove containing a water closet must be at least 30 inches wide to provide adequate clearance for the user. This dimension is measured between the finished side walls or partitions. Narrower alcoves do not meet the code minimum.

Question 34Plumbing Systems and Fixtures

A lavatory drain connects to a horizontal branch with a 1 1/2-inch trap. The trap arm slopes at 1/4 inch per foot. What is the maximum horizontal distance from the trap weir to the vent connection?

  1. 5 feet
  2. 3 feet
  3. 8 feet
  4. 6 feet Correct answer.

Explanation

The code limits a 1 1/2-inch trap arm to 6 feet of developed length when sloping at 1/4 inch per foot. The fall allowance and length limit must both be satisfied. A longer arm would require a revent or a larger trap size.

Question 35Plumbing Systems and Fixtures

A public restroom has a flushometer water closet and a lavatory on the same branch. What is the minimum fixture unit value assigned to the water closet for water supply sizing?

  1. 10 fixture units Correct answer.
  2. 2.5 fixture units
  3. 6 fixture units
  4. 4 fixture units

Explanation

A flushometer water closet is assigned 10 fixture units in the water supply sizing tables, reflecting its high peak demand. This value drives the branch and main sizing for public restrooms. Lower values apply to tank-type closets, not flushometer fixtures.

Question 36Plumbing Systems and Fixtures

A multi-story building has a 3-inch vertical soil stack serving water closets on four floors. What is the minimum size of the stack vent serving this stack?

  1. 3 inches
  2. 1 1/2 inches
  3. 2 inches Correct answer.
  4. 2 1/2 inches

Explanation

The stack vent must be sized according to the drainage stack it serves, and for a 3-inch soil stack the minimum stack vent is 2 inches. The vent must extend full size through the roof. Undersizing the vent would impair drainage and trap seal protection.

Question 37Water Supply and Distribution

Under the Ohio Plumbing Code, what is the minimum diameter of an individual water supply pipe serving a water closet?

  1. 1/2 inch
  2. 1 inch Correct answer.
  3. 3/4 inch
  4. 1-1/4 inches

Explanation

The Ohio Plumbing Code sets minimum fixture supply sizes in its water supply fixture unit tables. A water closet requires a minimum 1-inch individual supply pipe because of its high flush demand. Smaller sizes are permitted only for fixtures with lower fixture unit ratings.

Question 38Water Supply and Distribution

What is the minimum size of a building water supply main serving a single-family dwelling under Ohio rules?

  1. 1-1/2 inches
  2. 1 inch
  3. 1/2 inch
  4. 3/4 inch Correct answer.

Explanation

The code requires the water service and building supply main to be sized from the fixture unit load, but never smaller than 3/4 inch for a typical single-family dwelling. Larger sizes are required when the calculated demand exceeds the capacity of the 3/4-inch pipe.

Question 39Water Supply and Distribution

A water service pipe must be installed below the frost line. In Ohio, what is the typical minimum cover for a water service in areas with a 36-inch frost depth?

  1. 18 inches
  2. 36 inches Correct answer.
  3. 24 inches
  4. 12 inches

Explanation

Water service piping must be buried below the local frost depth to prevent freezing. Where the frost depth is 36 inches, the pipe must be at least that deep. Local jurisdictions may require greater depth, but the frost line is the baseline.

Question 40Water Supply and Distribution

Which device prevents backflow caused by backpressure in a potable water system?

  1. Reduced pressure zone assembly Correct answer.
  2. Vacuum breaker
  3. Air gap
  4. Pressure-reducing valve

Explanation

A reduced pressure zone assembly protects against both backsiphonage and backpressure because it maintains a lower pressure in the zone between two check valves. Vacuum breakers and air gaps primarily address backsiphonage. A pressure-reducing valve controls downstream pressure and provides no backflow protection.

Question 41Water Supply and Distribution

What is the purpose of a water pressure-reducing valve installed on a building supply?

  1. To lower excessive street pressure to a safe level for the distribution system Correct answer.
  2. To prevent water hammer in the service line
  3. To meter water consumption
  4. To increase flow velocity at fixtures

Explanation

When street pressure exceeds the safe limit for fixtures and piping, a pressure-reducing valve lowers it to a usable level, typically around 50 to 80 psi. Excessive pressure damages fixtures and causes noise and leaks. The valve does not meter, boost velocity, or arrest water hammer.

Question 42Water Supply and Distribution

A water heater is installed in a dwelling. Which requirement applies to the relief valve discharge pipe?

  1. It must discharge into the water closet tank.
  2. It must terminate not more than 6 inches above the floor or waste receptor. Correct answer.
  3. It may be reduced in size to match the drain.
  4. It may be capped to prevent scalding.

Explanation

The temperature and pressure relief valve discharge must terminate within 6 inches of the floor or a waste receptor and must not be trapped. The pipe must remain full size and must not be capped or threaded at the end. This allows safe discharge if the valve opens.

Question 43Water Supply and Distribution

What is the minimum air gap for a fixture indirectly connected to a drain, measured from the fixture outlet?

  1. One inch
  2. Two times the fixture outlet diameter Correct answer.
  3. Three inches
  4. One pipe diameter

Explanation

An air gap for an indirect waste must be at least two times the diameter of the fixture outlet but never less than 1 inch. This separation prevents sewage backup from reaching the potable or food-handling fixture.

Question 44Water Supply and Distribution

What is the primary function of an expansion tank on a closed potable water system?

  1. To filter sediment from the supply
  2. To reduce water hammer at the meter
  3. To store water for peak demand
  4. To absorb thermal expansion and protect the system from excess pressure Correct answer.

Explanation

In a closed system, heated water expands and cannot push back into the main. An expansion tank provides a compressible air cushion that absorbs the added volume, limiting pressure rise. It is not a storage, filtration, or hammer-arrest device.

Question 45Water Supply and Distribution

What is the minimum working pressure required at the fixture outlet for a properly operating plumbing system under typical code provisions?

  1. 4 psi
  2. 30 psi
  3. 15 psi
  4. 8 psi Correct answer.

Explanation

Fixtures are generally required to have at least 8 psi flowing pressure at the outlet to operate properly. Some fixtures such as flush valves require higher minimums. Less than 8 psi may cause inadequate flow and fixture malfunction.

Question 46Water Supply and Distribution

A water distribution system is being sized using the fixture unit method. Which factor most directly determines the size of a branch?

  1. The total fixture units on the branch and available pressure Correct answer.
  2. The diameter of the building drain
  3. The length of the longest run
  4. The number of occupants in the building

Explanation

Branch sizing depends on the fixture unit load carried and the available pressure at the point of connection. Longer runs add friction loss, but the governing inputs are demand and pressure. Occupancy and drain size do not size the supply branch.

Question 47Water Supply and Distribution

How is a water service pipe protected where it passes through a foundation wall below grade?

  1. It is wrapped in insulation only.
  2. It is provided with a sleeve or annular space and sealed to prevent seepage. Correct answer.
  3. It is encased in concrete for the full length.
  4. It is connected to the footing drain.

Explanation

Where a water service passes through a foundation, a sleeve or annular space is provided and the penetration is sealed to prevent water and termite entry. Encasing the full pipe in concrete or tying it to a drain is not required and may be prohibited.

Question 48Water Supply and Distribution

What is the maximum allowable velocity typically used when sizing a water distribution system to limit noise and erosion?

  1. 8 feet per second Correct answer.
  2. 5 feet per second
  3. 15 feet per second
  4. 2 feet per second

Explanation

Designers commonly limit water velocity to about 8 feet per second in supply piping to control noise, erosion, and pressure loss. Higher velocities accelerate wear and produce objectionable flow noise. Lower velocities are used where quiet operation is critical.

Question 49Water Supply and Distribution

A building has a flushometer water closet. What minimum fixture supply pressure is generally required for proper operation?

  1. 25 psi Correct answer.
  2. 8 psi
  3. 15 psi
  4. 10 psi

Explanation

Flushometer valves require higher pressure than gravity-tank fixtures to deliver a proper flush. Codes commonly require about 25 psi flowing pressure at the valve. Inadequate pressure causes weak or incomplete flushing.

Question 50Water Supply and Distribution

In a water distribution system, what does a pressure surge (water hammer) arrestor do?

  1. Removes dissolved air from the water
  2. Balances hot and cold supply pressures
  3. Absorbs the shock wave created when flow stops suddenly Correct answer.
  4. Increases pressure at the fixture

Explanation

When a valve closes quickly, the momentum of moving water creates a pressure surge. An arrestor contains a trapped air chamber or piston that absorbs the shock, reducing noise and pipe stress. It does not boost pressure or treat water quality.