SAIT PLUMBING SUPPLEMENT CODE APPENDIX COMBINED SEWERS

Summary

The National Plumbing Code of Canada (2020) provides guidelines for combined sewers, outlining conditions for sanitary drainage systems to connect to public combined sewers. The code emphasizes a preference for separate systems to address issues like combined sewer overflows. The video guides viewers through the process of sizing rainwater leaders and storm building drains using various formulas and tables. It includes step-by-step calculations for rainfall, hydraulic load, and fixture units, demonstrating how to combine sanitary and storm drainage systems, although separate systems are typically preferred. Key code references ensure compliance with the guidelines for proper sizing and installation.

Takeaways

• 😀 The National Plumbing Code of Canada, 2020 does not ban combined sewers, but sets specific guidelines for their use.
• 😀 Article 2.12.1 permits connections between sanitary drainage systems and public combined sewers under certain conditions.
• 😀 The code highlights a trend toward favoring separate sanitary and storm drainage systems to reduce combined sewer overflow issues.
• 😀 To determine the hydraulic load for combined drainage pipes, calculate fixture units and consider continuous flow sources.
• 😀 For drainage sizing, stormwater runoff from roofs and paved surfaces must be calculated and combined with the fixture load to determine the hydraulic load.
• 😀 Rainwater leaders are sized by calculating the total rainfall intensity and dividing by the number of leaders; for instance, two leaders draining from the same roof would split the total load in half.
• 😀 When sizing rainwater leaders, adjust for angled roofs by considering only 50% of the total rainfall intensity.
• 😀 For vertical walls or roofs, apply a similar calculation but divide the rainfall by 50% to account for angle considerations.
• 😀 When connecting stormwater drainage systems to a combined sewer, ensure to add converted sanitary fixture units as per the plumbing code.
• 😀 Even though a combined sewer system is possible under local authority approval, the code strongly prefers separating storm and sanitary systems to prevent future complications.

Q & A

What does the National Plumbing Code of Canada, 2020 say about combined sewers?

The National Plumbing Code of Canada, 2020 does not declare combined sewers illegal. Instead, it provides guidelines for their use, allowing sanitary drainage systems to connect to public combined sewers under specific conditions.

What does Article 2.12.1 of the code specify about combined sewers?

Article 2.12.1 allows sanitary drainage systems to connect to public combined sewers, but it includes limitations and considerations that reflect a trend toward favoring separate systems for sanitary and storm drainage to avoid combined sewer overflows.

How is the hydraulic load for combined drainage pipes calculated?

The hydraulic load is calculated by first determining the total load in fixture units from all fixtures, excluding continuous flow fixtures. If the load exceeds 260 fixture units, multiply by 9.1 to find the hydraulic load in liters. If the load is 260 or fewer fixture units, the load is 2360 liters.

What is the process for calculating the hydraulic load from roofs and paved surfaces?

The hydraulic load from roofs and paved surfaces is calculated similarly to storm drains, with the load being derived from the rainfall intensity and the area of the roof or paved surface.

What should be done if a roof has an angled surface?

For angled roofs, only 50% of the total rainfall intensity is considered in the calculation, meaning you multiply the height, length, and rainfall intensity, then divide by 50% to get the correct hydraulic load.

How are the rainwater leaders sized in this example?

Rainwater leaders are sized by calculating the hydraulic load for each section of the roof and then referring to the appropriate tables in the code. The size is determined based on the hydraulic load and the grade of the leader.

What happens when the hydraulic load exceeds 5,500 L?

When the hydraulic load exceeds 5,500 L, the size of the rainwater leaders must be increased. For example, in the transcript, when the load reaches 5,500 L, the rainwater leader size is increased to 5 inches.

How is the storm building drain sized after adding the sump?

After adding the storm sump, the storm building drain is sized by summing the hydraulic loads from the rainwater leaders and the sump. The size of the drain is then adjusted accordingly, with an 8-inch size required in the example provided.

What is the significance of converting fixture units into liters in the combined system?

In a combined system, the fixture units from the sanitary system must be converted into liters to ensure that the system handles the appropriate hydraulic load. This conversion is necessary to determine the correct size of the combined sewer.

What does the code say about constructing a combined sewer?

The code allows the construction of a combined sewer with permission from local authorities, but it is rare. The code generally prefers to separate storm and sanitary sewers to avoid potential issues like combined sewer overflows.