Canadian Code FAQs

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Doherty Plumbing

Journeyman & Gas Fitter
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Penticton, BC
Here is a list of some FAQ questions regarding the National Plumbing Code of Canada:

Potable Water

Does my house require a thermal expansion tank? Probably. If you have a check valve, PRV, or backflow preventer on your system you are required to have an expansion tank.

What is the highest PSI I am allowed for the water piping in my house? 550 kPa or 80 psi. If your incoming pressure is higher than that you are required to have a PRV installed by code.

Does my hot water tank require a vacuum breaker? Yes it does. All hot water tanks should be installed along with a vacuum breaker.

Does my hot water tank require a drain pan? If it is a storage type hot water tank then yes you require a drain pan that is not less than 50mm (2") larger in diameter then the tank itself. The drain pan must also have side walls that are not less than 25mm (1") tall.

If your drain pan is able to accept a drain (IE you can tie the pan into an existing soil-or-waste pipe) then that drain shall not be less than 2x the size of the relief valve on the tank. This would be a 1.5" drain on most standard hot water tanks. Your hot water tank shall also have a wilt tube (or similar) installed to direct any water, that is release, directly to the floor or drain pan.

Fixture Drains

What IS a fixture drain!? The NPC of Canada defines the fixture drain as the following:

"Fixture Drain means the pipe that connects a trap serving a fixture to another part of the drainage system."

How far can I run a fixture drain before I connect to another part of the drainage system?

6' for 1.5" piping.
8' for 2" piping.
12' for 3" piping.

How long can my fixture drain for my water closet be? 10' regardless of 3" or 4" piping.

Am I allowed to offset my fixture drain? Yes you can. But you are not allowed to have more then 135* of cumlitive change between the trap and the vent. For a toilet, or any other self-siphoning fixture, you are allowed 235* of cumlitive change.


Does every trap require a vent? The basic answer is yes! For every trap you have you need a vent for that trap. Either a dry vent or a wet vent.

Does every fixture need a trap? Yes and no. Sometimes fixtures are allowed to share a trap. Under certain conditions you can also have floor drains share a trap. Indirectly connected fixtures also do not require a trap.

Can I use an interceptor as a trap? Yes you can as long as it has an effective seal of not less than 38mm.

Wet Venting

Is wet venting allowed? Yes it is!

When is a vet vent most commonly used? Quite often actually. In Canada most bathrooms utilize wet venting to minimize the piping required to effectively drain and vent multiple fixtures in the same room.

What is the minimum wet vent when wet venting a toilet? 2".

May a wet vent extend through more then one story? Yes! But there are some specific rules you must adhere too. For example the wet vent shall not recieve the discharge of more then 4 fixture units from any one storey above the first storey.

Can I wet vent after the toilet? Quite simply.... No. You cannot wet vent passed a water closet.

What is the maximum length of a wet vent I can run? The length of a wet vent is not limited.

Minimum stand pipe for a washing machine: 600mm (24") and the stand pipe must terminate above the flood level rim of the washing machine.
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What is the Canadian plumbing code regarding vent pipes?

Is it that when extending through a roof the pipes shall be terminated at least (?) inches above the roof....?"

The International Residential Code says "open vent pipes that extend through a roof shall be terminated not less than 6 inches above the roof or 6 inches above the anticipated snow accumulation, whichever is greater....

Thanks, in advance, for your assistance.
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