SAIT PLUMBING SUPPLEMENT CODE APPENDIX STORM SIZING VERSION 2

Summary

This video explains the process of sizing and designing storm water drainage systems using specific code book tables. It covers how to calculate rainfall intensity, apply it to sizing both vertical (rainwater leader) and horizontal (storm building drain) pipes, and consider factors such as expansion joints. The example demonstrates the process for calculating the size of the rainwater leader and storm building drain, accounting for water flow from multiple rainwater leaders. The video also briefly touches on combined drainage systems, which integrate storm and sanitary systems.

Takeaways

• 😀 Storm sizing involves referencing specific code book tables for accurate design.
• 😀 Table 24109 is used for sizing storm and combined building drains, and it’s a horizontal table.
• 😀 Table 24111 helps size rainwater leaders, which are vertical pipes used to manage stormwater.
• 😀 Rainfall intensity (e.g., 20 mm over 15 minutes) is used to calculate the required capacity for drainage systems.
• 😀 The rainwater leader size is determined by multiplying rainfall intensity by the area (e.g., 20,000 liters).
• 😀 When sizing rainwater leaders, only the left two columns for circular leaders are used; ignore non-circular columns.
• 😀 An expansion joint should be installed within 5 feet of the roof hopper for proper drainage.
• 😀 As rainwater flows down the leader, it is guided through a series of pipes and joints, including a Y-connection.
• 😀 Storm building drains increase in size based on the volume of water collected from multiple rainwater leaders.
• 😀 A 1 in 100 grade column helps determine the size of storm building drains based on the total water collected.
• 😀 After combining the flow from multiple rainwater leaders, the drain size is increased to an 8-inch storm building drain to handle the higher load.

Q & A

What is the purpose of table 24109 in storm sizing?

Table 24109 is used for sizing storm and combined building drains, specifically the horizontal table for determining the appropriate size of storm drainage pipes.

What is the difference between table 24109 and table 24111?

Table 24109 is for sizing horizontal storm drains, while table 24111 is used for sizing rainwater leaders, which are vertical pipes for directing stormwater down the building.

What factors are used to size the rainwater leader in the example provided?

The sizing of the rainwater leader is based on the rainfall intensity, which in this example is 20 mm over 15 minutes, and the amount of water being drained, which is 10,000 liters per leader.

How do you calculate the total water flow for sizing the storm drain?

To calculate the total water flow, you multiply the rainfall intensity (20 mm) by the drainage area, and then sum the water flow from all rainwater leaders. For example, two leaders each draining 10,000 liters would give a total of 20,000 liters.

What is the size of the rainwater leader in the example, and how is it determined?

The rainwater leader is sized at 4 inches based on the total water flow (10,000 liters) and the guidelines in table 24111 for circular leaders.

Why is there an expansion joint in the rainwater leader?

An expansion joint is installed within 5 feet of the roof hopper to allow for thermal expansion and prevent damage to the piping system due to temperature changes.

How do you size the storm building drain after the rainwater leader exits the building?

After the rainwater leader exits the building, you refer to table 24109 and use the 1 in 100 grade column to find the appropriate size for the storm building drain. In this example, the combined water flow of 20,000 liters leads to a 6-inch pipe size.

What happens when two rainwater leaders are connected to the same storm building drain?

When two rainwater leaders are connected, their water flows are added together. For example, two leaders each draining 10,000 liters will result in a total flow of 20,000 liters, which will determine the size of the storm building drain.

How do you determine the final size of the storm building drain when two rainwater leaders are combined?

After adding the water flows from the two rainwater leaders, you refer back to table 24109 and find the corresponding size in the 1 in 100 grade column. For a combined flow of 20,000 liters, an 8-inch storm building drain is required.

What is the role of the exterior separate storm manhole in the system?

The exterior separate storm manhole is where the storm building drain discharges, effectively managing and directing the flow of stormwater from the building to the external drainage system.