Storm Drainage Systems (D-3) Flashcards
What is a Roof Drain?
- A fitting device that is installed in the roof
- Permits stormwater to drain into a Leader
What is the purpose of a Flow-Control Roof Drain?
- Used to drain the roof at a controlled rate (usually flows at a slower rate)
- The roof must be structurally designed to hold the excess rain water
What is a Siphonic Roof Drain?
- A drain that is designed to drain water faster which in turn creates a Siphonic condition.
- Because it drains water faster, minimal roof drains are required.
- can be connected into a single rain leader
What are Rainwater Leaders (RWL)?
- Located either inside or outside a building.
- Can be made from: sheet metal, non-circular tubing, or pipe
What is a Deck Drain?
- Same idea as a roof drain
- Has a flat strainer (instead of a dome shape)
- Located in areas like walkways
What is a Roof Gutter…
- Collection device
- Located at the lower side of pitched roof
- Made from: aluminum or steel w/ corrosion-resistant coating.
- Terminates at external leader
What is a Roof Scrupper?
- Boxlike collection device
- Located on exterior building
- Receives storm water on one side
What does an Emergency Roof Scrupper do?
- Are overflow protection for flat roofs
- Usually installed with flow control roof drains + parapet walls
What is a Catch Basin?
- Used to drain areas such as parking lots
- CB lead to storm sewars.
- Is designed ti trap debris to prevent it from entering the drainage pipe.
Storm drainage piping system….
- Designed for gravity or pumped flow to point of discharge
Who regulates the discharge rate for stormwater systems?
-Authority Having Jurisdiction
Lets talk aboot Combined Drainage Piping Systems
- Designed to collect storm drainage AND wastewater
- This is not an ideal set up as a heavy rainfall or snowmelt can overload the sewer system.
- These systems may employ combined sewer overflows (CSOs)
What is a Combined Sewer Overflow?
- Installed (sometimes) in Combined drainage pipiing systems)
- They are designed to overflow / discharge excess flow directly to a predetermined disposal area (ex: river) w/o reaching the sewage treatment plant.
When couplings for corrugated steel pipe are used what needs to be kept in mind?
- Maintaining pipe alignment
- Pipe separation doesn’t occur
- Root penetration doesn’t occur
- Keeps other material out
Where is corrugated steel galvanized pipe used?
For building sewers
Where are sheet metal leaders ued?
- Above ground outside only
What is all included in the storm drainage system?
- Rainwater leaders
- Storm / combined building drains
- storm / combined building sewers
What unit is used when measuring loads for the storm drainage system?
- Litres
How does the load of litres have a relationship with flow rate?
- A time frame is needed?
What time frame is used to calculate flow rate?
- 15 min
- Lires/ 15 min
How do you calculate the load in L/15 min from a roof or paved surface?
This is for Drainage Load for a Flat Surface
- Have to find the area that is being drained
- Multiply the area in metres squared (m2) by the rainfall intensity in mm/15 min
m2 x mm = 1L
Example on page 21
How do you solve Hydraulic load for a flat roof with an adjoining wall?
Drainage Load for a Flat surface with an Adjoining Wall
- Flat roof calculation = roof area (via area) x rainfall intensity.
- When calculating the wall, only one half of the wall has to be considered (as per code)
- wall calculation: Area = L x W, then divide by 2
m2 x mm = 1L –> L/15min = rainfall intensity
What happens when there are 2 or more adjoining walls?
Code states that only one-half of the largest adjoining wall area be considered.
How do you determine Loads from appliances that produce semi or continuous flow?
- Only fixtures or appliances that discharge clearwater waste may drain to a storm drainage system
- The flow rate of a fixture expressed in L/sec is multiplied by 31.7 to find the hydraulic load expressed in fixture units imposed on the sanitary system by that fixture.
