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Question 1General Plumbing Knowledge

Under the Uniform Plumbing Code, what is the minimum nominal size for a building drain serving a single-family dwelling?

  1. 1.5 inch
  2. 2 inch
  3. 3 inch Correct answer.
  4. 4 inch

Explanation

The building drain must be large enough to carry the total drainage load; for a single dwelling the minimum nominal diameter is 3 inch. Smaller sizes such as 1.5 or 2 inch are permitted only for branch lines, not the building drain.

Question 2General Plumbing Knowledge

What is the primary purpose of a plumbing vent installed on a drain line?

  1. To protect trap seals from siphonage and back pressure Correct answer.
  2. To filter debris before it enters the sewer
  3. To drain condensate from the fixture
  4. To increase water pressure at the fixture

Explanation

A vent admits air to the drainage system so that pressure in the pipe stays near atmospheric, which prevents trap seals from being siphoned out or pushed out. Protecting the trap seal is the defining function of venting.

Question 3General Plumbing Knowledge

A water heater's temperature and pressure relief valve discharge pipe must terminate:

  1. at least 6 inches above the floor or outside the building Correct answer.
  2. inside the flue connector
  3. below the water heater's cold inlet
  4. directly into the drain pan under the heater

Explanation

The T&P relief discharge must terminate in a safe place of disposal, typically not less than 6 inches above the floor or outside the structure, so scalding water and steam escape without injuring anyone. It must not be trapped or connected to the drainage system in a way that allows backflow.

Question 4General Plumbing Knowledge

Which material is typically joined by solvent cementing?

  1. PEX tubing
  2. PVC schedule 40 pipe Correct answer.
  3. Black steel pipe
  4. Type L copper tube

Explanation

PVC is a thermoplastic joined with solvent cement, which softens the surfaces and fuses them into a continuous joint. Copper, steel, and PEX rely on soldering, threading, or mechanical fittings respectively.

Question 5General Plumbing Knowledge

What is the standard slope for a 3-inch horizontal drainage pipe?

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

Explanation

Drainage pipe up to 3 inch is installed at a slope of 1/4 inch per foot, which provides adequate scouring velocity while keeping solids moving. Larger pipe may use 1/8 inch per foot, but 3 inch and smaller use the steeper standard.

Question 6General Plumbing Knowledge

A fixture's trap seal depth should be within which range?

  1. 1/2 inch to 1 inch
  2. 5 inches to 6 inches
  3. 2 inches to 4 inches Correct answer.
  4. 6 inches to 8 inches

Explanation

A trap seal must be deep enough to resist evaporation and pressure fluctuations but shallow enough to avoid excessive bacterial growth and odor; the standard range is 2 to 4 inches. Deeper seals are not permitted for ordinary fixtures.

Question 7General Plumbing Knowledge

Which of the following is the correct order of operations when installing a new water closet flange on a concrete floor?

  1. Set the closet bolt, pour the floor, install the flange
  2. Pour the floor, install the flange, install the closet bolts Correct answer.
  3. Install the closet bolts, install the flange, pour the floor
  4. Set the flange, install the closet bolts, pour the floor

Explanation

The concrete floor is placed first, then the closet flange is anchored to the finished floor or embedded per code, and the closet bolts are set into the flange slots before the fixture is lowered. Reversing this sequence prevents the flange from being secured properly.

Question 8General Plumbing Knowledge

The minimum size of a water service pipe for a single-family dwelling is generally:

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

Explanation

The water service pipe for a one- or two-family dwelling is commonly required to be not less than 3/4 inch nominal size to supply the required flow and pressure. A 1/2-inch service would be undersized for a whole house.

Question 9General Plumbing Knowledge

A cleanout is required at the upper end of a horizontal drainage pipe when the developed length exceeds:

  1. 20 feet Correct answer.
  2. 10 feet
  3. 50 feet
  4. 100 feet

Explanation

Where a horizontal drain run exceeds 20 feet in developed length, a cleanout must be installed at the upper end so the line can be rodded from both directions. Shorter runs can rely on the cleanout at the base of the stack.

Question 10General Plumbing Knowledge

A plumber is installing a lavatory drain that also serves as a vent for the fixture. This arrangement is known as:

  1. a stack vent
  2. a wet vent Correct answer.
  3. a circuit vent
  4. a yoke vent

Explanation

A wet vent is a vent that also serves as a drainage pipe for fixtures on the same or higher floor. A single lavatory drain that vents itself and another fixture is a classic wet vent arrangement.

Question 11General Plumbing Knowledge

Which factor most directly determines the required diameter of a gas vent connector from a residential water heater?

  1. The color of the vent pipe
  2. The input rating of the appliance and the height of the vent Correct answer.
  3. The type of floor drain installed nearby
  4. The water pressure at the fixture

Explanation

Vent connector sizing depends on the appliance input (BTU/hr) and the vent height and configuration, as shown in the sizing tables. The connector must be large enough to carry combustion products but not so large that it cools excessively.

Question 12General Plumbing Knowledge

A backflow preventer installed on a potable water line feeding a boiler must be:

  1. a simple check valve only
  2. a strainer only
  3. a pressure-reducing valve
  4. a reduced-pressure-zone assembly or equivalent approved device Correct answer.

Explanation

Boiler connections are a high-hazard cross-connection, so an approved reduced-pressure-zone backflow preventer or other approved device that protects against both backsiphonage and backpressure is required. A single check valve does not provide adequate protection.

Question 13General Plumbing Knowledge

A water heater is installed in an area subject to freezing. What minimum protection is required for the relief valve discharge and piping?

  1. No protection is required
  2. The relief valve may be removed in winter
  3. The heater must be drained completely
  4. The discharge pipe must be insulated or routed to prevent freezing Correct answer.

Explanation

Where freezing conditions exist, the relief valve discharge line must be protected, typically by insulation or routing, so that ice does not block the discharge and cause a dangerous pressure buildup. Removing the valve or draining the heater would defeat its purpose.

Question 14General Plumbing Knowledge

A horizontal branch drain serving a water closet must be sized to carry which load?

  1. The total building drainage load
  2. The vent load of the stack
  3. The fixture units of all fixtures draining into that branch Correct answer.
  4. Only the water closet's fixture units

Explanation

A branch drain must be sized for the total fixture units of every fixture it serves, not just the largest fixture. Sizing for only the water closet would undersize the pipe and cause backups.

Question 15General Plumbing Knowledge

The purpose of a trap primer is to:

  1. Prevent freezing in the supply line
  2. Remove sediment from the water heater
  3. Increase the flow rate through a fixture
  4. Add water to a floor drain trap to maintain its seal Correct answer.

Explanation

A trap primer supplies a small amount of water to a rarely used trap, such as a floor drain, so the seal does not evaporate and allow sewer gas into the building. It does not affect flow rate, freezing, or sediment.

Question 16General Plumbing Knowledge

A plumber is connecting a dishwasher to the drainage system. Which method protects against backflow of wastewater into the dishwasher?

  1. A check valve in the supply line
  2. An air gap or a high-loop drain connection Correct answer.
  3. A direct connection to the sink drain without an air gap
  4. A vacuum breaker on the water heater

Explanation

Dishwasher drainage must be protected by an air gap or by routing the drain hose through a high loop above the flood level rim of the sink, which prevents wastewater from siphoning back into the appliance. A direct connection without protection is a cross-connection.

Question 17General Plumbing Knowledge

When installing a water service line, the minimum cover depth is generally determined by:

  1. The color of the pipe
  2. The local frost line and soil conditions Correct answer.
  3. The size of the water meter
  4. The number of fixtures served

Explanation

Water service lines must be buried below the local frost line, or otherwise protected from freezing, and deep enough to avoid damage from surface loads. Meter size and fixture count do not determine burial depth.

Question 18General Plumbing Knowledge

A stack serving more than one story must be supported at:

  1. Only at the base
  2. The base and at intervals not exceeding the code maximum Correct answer.
  3. No support is required
  4. Only at the top

Explanation

Vertical stacks must be supported at their base and at intervals along their height so the weight of the pipe and its contents is not carried by the fittings alone. Supporting only at the top or base leaves the stack unstable.

Question 19General Plumbing Knowledge

Which condition would cause a plumbing trap to lose its seal through back pressure?

  1. A leaking supply valve
  2. A worn flapper in a toilet tank
  3. A clogged aerator
  4. A blocked vent on a nearby fixture Correct answer.

Explanation

Back pressure occurs when air pressure in the drainage system exceeds atmospheric pressure and pushes the trap seal out. A blocked or inadequate vent can cause this by preventing pressure equalization, while supply-side and fixture-part problems do not affect the drainage pressure.

Question 20General Plumbing Knowledge

A plumber must install a water heater in a seismic zone. What additional requirement applies to the tank?

  1. The tank must be disconnected from the gas line
  2. The tank must be strapped to the structure Correct answer.
  3. The tank must be installed upside down
  4. The tank must be painted a specific color

Explanation

In seismic zones, water heaters must be anchored or strapped to the building structure to prevent them from tipping and rupturing gas or water connections during an earthquake. Color, orientation, and disconnection are not code requirements.

Question 21General Plumbing Knowledge

A building's drainage system is being tested with water. The test must maintain a water level of at least:

  1. 10 feet above the highest point of the system
  2. 1 foot above the highest point of the system
  3. 5 feet above the highest point of the system Correct answer.
  4. The height of the building

Explanation

A water test for the drainage system requires the piping to be filled and maintained at least 5 feet above the highest point of the section under test for the specified duration. This head pressure reveals leaks at joints and fittings.

Question 22General Plumbing Knowledge

A plumber finds that a lavatory drains slowly and gurgles, but the trap is clear. Which diagnosis best fits a venting problem?

  1. The water heater is set too low
  2. The toilet flapper is leaking
  3. The supply pressure is too high
  4. The trap arm is too long or improperly vented, causing the trap to siphon Correct answer.

Explanation

Gurgling and slow drainage with a clear trap point to a venting deficiency: an overlong trap arm or missing vent allows the trap to siphon and the fixture to drain sluggishly. Supply pressure, heater settings, and toilet parts do not produce this pattern.

Question 23General Plumbing Knowledge

A plumber is sizing a gas line for a range and a water heater on the same branch. Which method is correct?

  1. Ignore the range because it is intermittent
  2. Add the BTU input of both appliances and size for the total with the appropriate length and pressure drop Correct answer.
  3. Size the line by the pipe diameter of the meter outlet
  4. Size the line for the larger appliance only

Explanation

Gas line sizing uses the total connected load, so the BTU inputs of all appliances on the branch are added and the pipe is sized using the longest length and allowable pressure drop from the tables. Sizing for one appliance or ignoring an intermittent appliance can starve the system.

Question 24General Plumbing Knowledge

A multi-story building has a soil stack with horizontal branches on each floor. What is the maximum number of fixture units allowed on a branch before additional venting is needed?

  1. Always 2 fixture units
  2. Determined only by the building height
  3. Always 10 fixture units
  4. Determined by the branch size and the venting tables for the specific fixture group Correct answer.

Explanation

Branch load limits depend on the pipe size, the type of fixtures, and the venting arrangement, so the applicable venting and sizing tables must be consulted for the specific installation. Fixed numbers or building height alone cannot determine the limit.

Question 25General Plumbing Knowledge

A commercial kitchen requires a grease interceptor. Which statement about its installation is correct?

  1. It may be omitted if a floor drain is present
  2. It may be installed upstream of the fixtures
  3. It must be installed downstream of the fixture drains and sized for the flow and grease load Correct answer.
  4. It replaces the need for a vent

Explanation

A grease interceptor is installed on the drainage line downstream of the fixtures it serves and must be sized for the expected flow rate and grease load so fats, oils, and grease are separated before entering the sewer. It does not replace venting, and a floor drain does not eliminate the requirement.

Question 26General Plumbing Knowledge

A plumber is installing a new fixture drain and needs to select a trap arm. Which statement correctly describes the function of a fixture trap?

  1. It maintains a water seal that blocks sewer gas from entering the building. Correct answer.
  2. It filters solid waste before it enters the branch drain.
  3. It regulates the flow rate of water leaving the fixture.
  4. It stores water so that the fixture can operate during a supply interruption.

Explanation

A fixture trap holds a small volume of water in its dip that acts as a barrier, preventing sewer gases and airborne bacteria from backing into the occupied space. The seal is maintained by the trap depth and protected by proper venting. Traps are not designed for storage, filtration, or flow regulation.

Question 27General Plumbing Knowledge

A plumber is joining two lengths of copper tube for a domestic water line using lead-free solder. Which operation must be performed immediately before applying heat?

  1. Coat the tube end with pipe dope.
  2. Apply flux to the cleaned tube end and fitting socket. Correct answer.
  3. Wrap the joint with thread seal tape.
  4. Fill the tube with water to prevent overheating.

Explanation

Solder will not bond to oxidized copper, so the tube end and fitting socket must be cleaned to bright metal and coated with flux before heating. Flux removes remaining oxide and helps the solder flow into the joint by capillary action. Thread tape and pipe dope are used on threaded joints, not soldered ones.

Question 28General Plumbing Knowledge

A plumber is installing a water closet in a commercial restroom. What is the standard rough-in dimension measured from the finished wall to the center of the closet flange for a typical floor-mounted water closet?

  1. 10 inches
  2. 12 inches Correct answer.
  3. 14 inches
  4. 16 inches

Explanation

Most floor-mounted water closets use a 12-inch rough-in, meaning the center of the closet flange sits 12 inches from the finished wall. This leaves room for the tank behind the bowl. Other rough-ins exist for special models, but 12 inches is the standard residential and commercial dimension.

Question 29General Plumbing Knowledge

A plumber is checking the slope of a 3-inch horizontal building drain. What slope is generally required for proper drainage?

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

Explanation

Horizontal drainage piping up to 3 inches is typically installed at a slope of 1/4 inch per foot (about 2 percent), which provides adequate velocity to carry solids while keeping liquids from outrunning them. Larger pipes may use 1/8 inch per foot. Too flat a slope allows solids to settle and too steep a slope leaves liquids behind.

Question 30General Plumbing Knowledge

A plumber is installing a vent through a roof in a cold climate. What is the minimum distance the vent must extend above the roof surface to reduce the chance of frost closure?

  1. 6 inches Correct answer.
  2. 2 inches
  3. 12 inches
  4. 18 inches

Explanation

Vent terminals must extend at least 6 inches above the roof surface, and in areas subject to heavy snow or frost, the pipe is often increased in size to resist frost closure. The 6-inch minimum keeps the opening clear of normal snow accumulation. Local codes may require more, but 6 inches is the general minimum.

Question 31General Plumbing Knowledge

A plumber is installing a pressure-reducing valve on a domestic water service where the street pressure is 110 psi. What is the primary purpose of this valve?

  1. To maintain a constant flow rate regardless of demand.
  2. To prevent backflow of water into the public main.
  3. To lower the pressure to a safe level for fixtures and piping. Correct answer.
  4. To remove sediment from the incoming water.

Explanation

A pressure-reducing valve protects the piping and fixtures from excessive supply pressure, typically limiting downstream pressure to about 50 to 80 psi. High pressure accelerates wear on fixtures and can cause water hammer. Backflow prevention and sediment removal are handled by separate devices.

Question 32General Plumbing Knowledge

A plumber is testing a newly installed DWV system with water. Which condition must be met before the test is accepted?

  1. The entire system holds the test water level for the required duration with no leaks. Correct answer.
  2. The water level is allowed to drop as the system absorbs water.
  3. The test is performed with compressed air instead of water.
  4. Only the vertical stacks are filled with water.

Explanation

A water test of a DWV system requires that all openings be sealed, the system filled to the required level, and that level held for the required time with no drop and no visible leaks. A drop in level or any leak indicates a defect that must be corrected before the test is accepted. Testing only stacks or using air does not satisfy a water test requirement.

Question 33General Plumbing Knowledge

A plumber is installing a water heater and must connect the temperature and pressure relief valve. Where should the discharge pipe terminate?

  1. At a point where it can drain by gravity to a safe location, with no trap or reduction in size. Correct answer.
  2. Into a closed container that is sealed from the atmosphere.
  3. Directly into the drainage system through a trapped connection.
  4. At a height above the heater so it can be inspected easily.

Explanation

The T&P relief valve discharge must terminate in a safe place where it can drain by gravity, with the pipe full size and no trap, so that it cannot be blocked or hold water. A trapped or reduced discharge could prevent relief and cause a tank rupture. The discharge must also be directed to prevent scalding injury.

Question 34General Plumbing Knowledge

A plumber is installing a floor drain in a commercial kitchen. What is the purpose of the trap primer connected to this drain?

  1. To allow the trap to be cleaned without removing the strainer.
  2. To keep the trap seal from evaporating during periods of no use. Correct answer.
  3. To increase the flow rate of wastewater leaving the floor drain.
  4. To prevent grease from entering the trap.

Explanation

A floor drain that sees little use can lose its trap seal through evaporation, allowing sewer gas into the building. A trap primer delivers a small amount of water to the trap on a regular basis to maintain the seal. It does not affect flow rate, grease handling, or cleaning access.

Question 35General Plumbing Knowledge

A plumber is installing a shower valve in a multifamily building. Which feature is required to protect the bather from a sudden temperature change when another fixture is used?

  1. A single-handle valve without a balancing mechanism.
  2. A pressure-balancing or thermostatic mixing valve. Correct answer.
  3. A gate valve on the hot supply.
  4. A check valve on the cold supply only.

Explanation

Shower valves must limit temperature swings caused by pressure changes elsewhere in the system, and pressure-balancing or thermostatic mixing valves accomplish this. A plain single-handle valve without balancing does not protect the bather. A gate valve or a single check valve does not balance hot and cold pressures.

Question 36General Plumbing Knowledge

A plumber is sizing a water distribution system for a building. Which factor most directly affects the minimum pipe size selected for a branch serving several fixtures?

  1. The total fixture units and the available pressure. Correct answer.
  2. The building's occupancy classification alone.
  3. The length of the vent stack.
  4. The color of the pipe and the type of insulation.

Explanation

Water pipe sizing depends on the demand load expressed in fixture units and on the pressure available at the source after accounting for friction loss and elevation. The combination determines the minimum diameter that will deliver adequate flow. Pipe color, insulation, occupancy alone, and vent length do not determine supply pipe size.

Question 37General Plumbing Knowledge

A plumber is installing a backwater valve on a basement floor drain in a building where the public sewer may surcharge. How should the valve be oriented and maintained?

  1. It should be buried under the slab with no access.
  2. It should be installed so flow in the normal direction opens it, and it must remain accessible for cleaning. Correct answer.
  3. It should be installed on the vent pipe above the fixture.
  4. It should be installed backward so that sewage can escape the building.

Explanation

A backwater valve is installed so that normal flow opens the flapper and reverse flow closes it, preventing sewage from backing into the building. It must remain accessible for inspection and cleaning because debris can prevent it from seating. Installing it backward, burying it, or placing it on a vent defeats its purpose.

Question 38General Plumbing Knowledge

A plumber is installing a sump pump in a basement. The pump discharges through a check valve and then to the exterior. What is the purpose of the check valve in this installation?

  1. To prevent the pump from drawing air at startup.
  2. To prevent the pumped water from draining back into the sump when the pump stops. Correct answer.
  3. To reduce the discharge pressure at the outlet.
  4. To filter debris before it reaches the pump.

Explanation

The check valve holds the water in the discharge line so that it does not flow back into the sump and cause the pump to cycle repeatedly. It also protects the pump from the water hammer of reverse flow. It does not prime the pump, reduce pressure, or filter debris.

Question 39General Plumbing Knowledge

A plumber is installing a grease interceptor for a restaurant. Which installation practice is correct?

  1. The interceptor is installed on the potable water supply to the kitchen.
  2. The interceptor is installed below the slab with the cover permanently sealed.
  3. The interceptor is installed on the discharge side of the building sewer.
  4. The interceptor is installed so that it can be serviced and its cover removed without disturbing fixtures. Correct answer.

Explanation

A grease interceptor must be accessible for periodic pumping and cleaning, so its cover must be removable and its location must allow service access. It is installed on the drainage line from the fixtures it serves, ahead of the building sewer connection. It is never installed on a potable water line.

Question 40General Plumbing Knowledge

A plumber is installing a lavatory faucet and notices that the hot water is on the right side. Why is this considered incorrect?

  1. Faucets are not permitted to have separate handles.
  2. The hot supply must be connected to the drain line.
  3. Hot water must always be supplied through a larger pipe.
  4. The standard convention is hot on the left and cold on the right. Correct answer.

Explanation

Plumbing fixtures follow the long-standing convention of hot water on the left and cold on the right, which allows users to operate fixtures consistently and reduces the risk of scalding. This convention applies to faucets, valves, and supply stops. Pipe sizing, handle type, and drain connections are unrelated to this rule.

Question 41Plumbing Systems and Fixtures

What is the minimum required diameter of a water closet drain pipe under a standard plumbing code?

  1. 3 inches Correct answer.
  2. 1.5 inches
  3. 2 inches
  4. 4 inches

Explanation

A water closet must be connected to a drain of at least 3 inches in diameter so that solids and the large flush volume can pass without clogging. Smaller sizes such as 2 inches are used for lavatories and other fixtures, not for toilets.

Question 42Plumbing Systems and Fixtures

A plumbing code requires a water closet to have a water consumption of no more than how many gallons per flush for a standard tank-type fixture?

  1. 1.6 gallons Correct answer.
  2. 3.5 gallons
  3. 1.28 gallons
  4. 2.5 gallons

Explanation

The federal standard for new tank-type water closets is 1.6 gallons per flush, a limit adopted into most plumbing codes. Higher values such as 3.5 gallons reflect older fixtures that are no longer installed in new construction.

Question 43Plumbing Systems and Fixtures

What is the primary purpose of a trap in a plumbing fixture drain?

  1. To increase the velocity of the discharge
  2. To maintain a water seal that blocks sewer gas Correct answer.
  3. To filter solid waste from the drainage
  4. To regulate the temperature of the drain water

Explanation

A trap holds a water seal in its dip that prevents sewer gases and odors from entering the building through the fixture drain. The depth of the seal, typically 2 to 4 inches, is what makes the trap effective.

Question 44Plumbing Systems and Fixtures

Which fixture requires a minimum drain size of 1.25 inches rather than 1.5 inches?

  1. Water closet
  2. Floor drain
  3. Bathtub
  4. Lavatory Correct answer.

Explanation

A lavatory is permitted a minimum trap and drain arm of 1.25 inches because its waste load is small. Bathtubs, floor drains, and water closets all require larger minimum drain sizes.

Question 45Plumbing Systems and Fixtures

What is the standard maximum water pressure at a fixture in a building water distribution system?

  1. 100 psi
  2. 80 psi Correct answer.
  3. 50 psi
  4. 125 psi

Explanation

Plumbing codes limit static pressure at fixtures to about 80 psi to protect fixtures and appliances from damage. Where supply pressure exceeds this limit, a pressure-reducing valve must be installed.

Question 46Plumbing Systems and Fixtures

A floor drain serving a public restroom must be provided with what feature to prevent sewer gas from entering when the trap seal evaporates?

  1. An air admittance valve
  2. A cleanout plug
  3. A trap primer Correct answer.
  4. A backwater valve

Explanation

A trap primer automatically replenishes the water in a floor drain trap so the seal does not evaporate during dry periods. Without it, the trap can dry out and allow sewer gas into the space.

Question 47Plumbing Systems and Fixtures

What is the required air gap between a fixture outlet and the flood-level rim of a fixture?

  1. There is no minimum as long as the outlet is above the rim
  2. At least 4 inches regardless of outlet size
  3. At least 1 inch or twice the outlet diameter, whichever is greater Correct answer.
  4. Exactly one-half the outlet diameter

Explanation

The minimum air gap is defined as twice the effective opening of the outlet, with a minimum of 1 inch. This separation prevents backflow by ensuring a physical break between the supply and the fixture.

Question 48Plumbing Systems and Fixtures

A lavatory faucet in a public restroom is rated at 2.2 gpm. Which statement best describes compliance with current fixture efficiency standards?

  1. It exceeds the 1.5 gpm maximum allowed for public lavatory faucets Correct answer.
  2. It exceeds the 0.5 gpm maximum allowed for public lavatories
  3. It complies because 2.2 gpm is the standard for public lavatories
  4. It complies only if the faucet is metered

Explanation

Public lavatory faucets are limited to 1.5 gpm at 60 psi under current efficiency standards. A 2.2 gpm faucet would not meet the requirement and would need to be replaced or restricted.

Question 49Plumbing Systems and Fixtures

What is the primary function of a backwater valve in a building drain?

  1. To separate gray water from black water
  2. To reduce the velocity of discharge entering the sewer
  3. To prevent sewage from reversing into the building during a surcharge Correct answer.
  4. To vent the drainage system to the outdoors

Explanation

A backwater valve is a check valve installed on the building drain that closes when flow reverses, protecting the building from sewage backup during a public sewer surcharge. It must be installed in an accessible location for maintenance.

Question 50Plumbing Systems and Fixtures

A water heater is installed in a building and the temperature and pressure relief valve discharge pipe terminates 6 inches above the floor drain. What is the most significant concern with this installation?

  1. The pipe should terminate at least 12 inches above the floor
  2. The discharge pipe should not be trapped or reduced and must terminate in a safe manner Correct answer.
  3. The pipe must be connected directly to the drain
  4. The valve should be capped to prevent leakage

Explanation

The T&P relief discharge must remain full size, must not be trapped, and must terminate in a location where hot discharge will not cause injury. A 6-inch air gap above a floor drain is generally acceptable, but the pipe must not be reduced or trapped.