Mixed Deck — All 306A Topics Flashcards

What is the minimum capacity of a residential water heater for a family of four?

Answer: 190 litres (50 gallons)

A 190-litre (50-gallon) water heater is generally recommended as the minimum for a family of four to provide adequate hot water for multiple bathrooms, laundry, and kitchen use during peak demand periods.

What pipe material is most commonly used for interior residential natural gas piping in Canada?

Answer: Black steel (iron) pipe

Black steel (iron) pipe with threaded fittings is the most common material for interior natural gas piping. It is strong, durable, and approved for gas service. Galvanized pipe is not recommended because the zinc coating can flake off and clog gas valve orifices.

When installing a kitchen sink, what type of strainer assembly is typically used?

Answer: Basket strainer assembly with a compression seal and locknut

A basket strainer assembly with plumber's putty or silicone seal, a rubber gasket, and a locknut is the standard installation for kitchen sinks. The removable basket catches food debris to prevent drain blockages.

Which joining method is NOT rated for pressurized copper water supply piping and therefore cannot be used on supply lines?

Answer: No-hub (Mission-type) banded rubber couplings — rated for drain, waste, and vent piping only, not pressure piping

No-hub couplings are designed for low-pressure gravity drain piping and are not rated for the working pressures found in domestic water supply systems.

What valve type is NOT acceptable as an isolation valve on a water supply branch because it restricts flow?

Answer: Globe valve

A globe valve creates significant flow restriction due to its internal design, which forces water to change direction through the valve body. Ball and gate valves provide full-port (unrestricted) flow and are preferred for isolation.

After cutting rigid PVC pipe with a hacksaw for a solvent-cemented joint, what must be done to the pipe end before applying primer?

Answer: Deburr and chamfer the pipe end to ensure full insertion and avoid scraping cement from the socket

Deburring and chamfering removes sharp edges that would scrape cement from socket walls and ensures the pipe seats to full depth for a strong solvent bond.

What is the purpose of a check valve on the cold water inlet to a water heater?

Answer: To prevent hot water from migrating back into the cold water supply

A check valve on the cold water inlet prevents thermosiphoning, where heated water rises back into the cold water line, causing energy waste and potentially delivering hot water to cold-water fixtures.

When installing a gas water heater in a confined space, how must combustion air be supplied?

Answer: Through dedicated air openings — one high and one low — connected to the outdoors or to a larger interior space

A confined space requires two permanent openings — one within 300 mm of the ceiling and one within 300 mm of the floor — to provide adequate combustion air. These openings must connect to the outdoors or to a sufficiently large interior space.

What is the minimum insulation R-value required for hot water supply piping in most Canadian energy codes?

Answer: R-3 to R-4 depending on pipe size

Canadian energy codes generally require R-3 to R-4 insulation on hot water supply piping, depending on the pipe diameter, to reduce heat loss and conserve energy.

What is 'induced siphonage' in a drainage system?

Answer: Trap seal loss caused by the discharge of another fixture on the same branch

Induced siphonage occurs when a nearby fixture discharges and creates negative pressure in the shared branch drain, pulling the trap seal from an adjacent, non-discharging fixture. Proper branch venting prevents this.

What material should be used to seal the joint between a lavatory pop-up drain and the basin?

Answer: Plumber's putty or silicone sealant around the drain flange

Plumber's putty (or silicone sealant on certain basin materials like marble or cultured stone) is applied around the drain flange to create a watertight seal between the drain body and the lavatory basin.

What is the purpose of a 'proof of closure' switch on a gas safety valve?

Answer: To verify that the safety shut-off valve has fully closed before allowing the ignition sequence to begin

A proof of closure switch confirms that the gas safety shut-off valve is fully closed before the controller allows a new ignition cycle to begin. This prevents unburned gas from accumulating if the valve failed to close completely during the previous shutdown.

Why should plumber's putty NOT be used on certain types of stone or composite sinks?

Answer: The oils in plumber's putty can stain or damage porous stone and certain composite materials

Plumber's putty contains oils that can leach into porous stone (marble, granite, limestone) and certain composite materials, causing permanent stains or discolouration. Silicone sealant should be used instead for these materials.

What is the purpose of a hot water recirculation system?

Answer: To provide near-instant hot water at fixtures far from the heater by continuously circulating hot water

A recirculation system uses a pump and return line to keep hot water moving through the distribution piping, so hot water is available almost immediately at remote fixtures without wasting water waiting for it to arrive.

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

Answer: Two pipe diameters or 25 mm, whichever is greater

The Code requires an air gap of at least two pipe diameters or 25 mm, whichever is greater, to prevent cross-connection and backflow contamination.

What is a 'stack vent' in plumbing terminology?

Answer: The extension of a soil or waste stack above the highest horizontal branch connection

A stack vent is the extension of a soil or waste stack above the highest horizontal drain branch connection. It continues upward through the roof to serve as a vent for the stack.

According to the Code, what is the maximum distance a P-trap can be from the vent connection?

Answer: 1.2 m for 1¼ inch trap

The Code limits the trap-to-vent distance to 1.2 m for a 1¼-inch trap arm to maintain the trap seal and prevent siphonage.

Why must a vent pipe always rise above the fixture flood level rim before connecting horizontally to the vent stack?

Answer: To prevent waste water from flowing into the vent during a fixture backup

The vent must rise above the fixture flood level rim before running horizontally to ensure that waste water cannot enter the vent pipe if the fixture backs up or overflows.

What is the hazard of operating a gas appliance with a cracked heat exchanger?

Answer: Products of combustion, including carbon monoxide, can enter the living space through the crack

A cracked heat exchanger allows combustion gases, including deadly carbon monoxide, to mix with the heated air being distributed through the home. This is an immediate life-safety hazard requiring the appliance to be shut down.

What is a 'heat pump' water heater?

Answer: A water heater that extracts heat from ambient air and transfers it to the water, operating like a refrigerator in reverse

A heat pump water heater uses a refrigeration cycle to extract heat energy from the surrounding air and transfer it to the water in the tank. It is 2 to 3 times more efficient than a conventional electric resistance heater.