306A Cheat Sheet 2026

The 30 highest-yield 306A facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What is the minimum pipe size for a building sewer according to the National Plumbing Code of Canada? → 4 inch
2. What is the minimum hot water supply temperature at a residential fixture outlet according to Canadian plumbing standards? → 43°C
3. What is the maximum permitted flush volume for a residential water closet under current Canadian standards? → 6.0 L per flush
4. When joining ABS or PVC drain pipe with solvent cement, what motion is used when inserting the pipe into the socket? → Give the pipe a quick quarter-turn while pushing to full depth, then hold without rotation
5. What is the recommended frequency for flushing sediment from a residential water heater? → Every 6 to 12 months
6. What type of venting material is required for a high-efficiency condensing gas water heater? → PVC or CPVC plastic vent pipe
7. What is a 'crown vent'? → A vent connected at the crown (top bend) of a trap
8. What compound or sealant is approved for use on threaded gas pipe joints? → Pipe joint compound or Teflon tape specifically rated for gas service
9. What material should be used to seal the joint between a lavatory pop-up drain and the basin? → Plumber's putty or silicone sealant around the drain flange
10. Where must the discharge pipe from a T&P relief valve terminate? → Within 150 mm of the floor or to an approved indirect waste receptor, with an air gap
11. What minimum slope is required for a 4-inch horizontal drainage pipe in the National Plumbing Code of Canada? → 1 in 50 (2%)
12. What is the minimum insulation R-value required for hot water supply piping in most Canadian energy codes? → R-3 to R-4 depending on pipe size
13. What is the odorant added to natural gas so that leaks can be detected by smell? → Mercaptan (methyl mercaptan or ethyl mercaptan)
14. What is the primary concern when sizing a horizontal storm drain? → The projected roof area drained and local rainfall intensity
15. What test is performed on a finished water closet installation to check for leaks at the wax ring seal? → Fill the bowl with dyed water and check for leaks at the floor connection
16. What is the proper height for a shower head in a standard residential shower? → 2000 mm (6 feet 8 inches) from the shower floor
17. What is the minimum burial depth for a water service pipe in most Canadian jurisdictions? → At or below the local frost depth
18. What valve type is NOT acceptable as an isolation valve on a water supply branch because it restricts flow? → Globe valve
19. What type of wax seal is recommended for a water closet installed on a flange that is below the finished floor level? → Extra-thick wax ring or stacked wax rings
20. What is the standard rough-in height for a tub spout? → 100 mm (4 inches) above the tub rim
21. When connecting two drainage pipes at a junction, why is a wye and 45-degree bend preferred over a tee? → It provides a smoother flow transition and reduces turbulence
22. What is the maximum allowable pressure drop in a residential gas piping system from the meter to the most remote appliance? → 0.25 kPa (1 inch WC)
23. What is the proper torque sequence when tightening the closet bolts on a water closet? → Alternate between bolts, tightening gradually and evenly until snug
24. What is the fixture unit value assigned to a domestic kitchen sink by the Code? → 2 fixture units
25. What test pressure is required for a DWV system rough-in test using water according to the Code? → A column of water at least 3 m high or 30 kPa
26. What is the purpose of a check valve on the cold water inlet to a water heater? → To prevent hot water from migrating back into the cold water supply
27. According to the National Plumbing Code of Canada, what is the minimum clearance in front of a water closet? → 550 mm
28. What is the minimum grade required for a vent pipe that runs horizontally? → 1 in 100 back toward the drainage pipe it serves
29. What safety device prevents a gas water heater from operating if the flue is blocked? → A spill switch or blocked vent safety shutoff that detects exhaust gas spillage
30. What fitting is required when connecting a horizontal branch to a vertical soil stack? → Sanitary tee or wye fitting