Learn more about creating a building's gas and storm riser diagrams, explaining how they depict the flow of gas and rainwater, respectively. The gas riser shows the route of natural gas from the city supply to the building's various fixtures, while the storm riser diagram outlines how rainwater drains from the roof to the street's storm system.
Key Insights
- The gas riser diagram displays the gas service into the building, the gas piping, any required venting, and how the piping gets carried to fixtures that require gas. It also includes a natural gas equipment demand schedule.
- The fixtures that typically require gas include domestic water heaters, water heaters, and certain kitchen equipment like convection ovens and tilting skillets. The gas is delivered to these fixtures via a metering system and pressure-reducing valves to ensure proper handling within the building.
- The storm riser diagram, on the other hand, outlines the drainage of stormwater from the building, starting at the roof level with roof drains, then traveling down through various sizes of piping, to finally tie into the storm management system under the street.
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After working through sanitary riser information, the next riser sheets typically shift into other plumbing systems that support building operations. Two major ones are the gas riser diagram and the storm riser diagram. Each diagram focuses on a specific system, showing how service enters the building, how piping is distributed, and how the system connects to fixtures or discharge points.
Riser diagrams are especially useful because they provide a clear “system story.” Instead of only showing where piping runs on a floor plan, they help you understand how the system is organized vertically and how it connects from source to endpoint.
Gas Riser Diagram: How Fuel Service Reaches Building Equipment
The gas riser diagram shows the complete gas system for the project, including:
- Gas service entry into the building
- Metering components used to measure consumption
- Pressure reduction to ensure safe, usable building pressure
- Gas piping distribution and pipe sizing
- Connections to gas-fired equipment
Start with the Demand: What Needs Gas?
One of the most helpful references on the gas riser sheet is the natural gas equipment demand schedule. This schedule tells you what fixtures and equipment require gas on the project. Typical examples include domestic water heating equipment and certain kitchen appliances.
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In this case, the demand schedule highlights gas-fired equipment such as:
- Domestic water heater and other water heating equipment
- Kitchen equipment, including items like a convection oven and a tilting skillet
Once you know which equipment requires gas, it becomes much easier to trace the diagram and understand why the piping branches where it does.
Tracing the Gas Service into the Building
Pressure-reducing with the natural gas service entering the building from the municipal supply. That incoming service typically passes through a metering system, then through pressure reducing valves that ensure the gas enters the building distribution system at a pressure the interior piping and connected equipment can safely handle.
Understanding Pipe Information on the Diagram
Gas risers often include pipe sizing and run information along the branches. You may see:
- Pipe diameters called out along each segment
- Run lengths or distance information associated with segments
These callouts show how the system is sized as it branches out to serve different equipment. From the service entry, piping routes toward the kitchen equipment that needs gas and also branches to serve the water heating equipment.
What the Gas Riser Helps You Confirm
- Where gas enters the building and what components handle it first
- How pressure and metering are handled before distribution
- How the piping branches to reach each gas-fired fixture or piece of equipment
- What pipe sizes are intended along the system path
Storm Riser Diagram: How Rainwater Leaves the Building
After reviewing domestic water, sanitary, and gas systems, the storm riser diagram completes another essential plumbing story: how stormwater drains from the roof and exits the building.
The storm system is responsible for collecting rainwater and directing it into the storm infrastructure, typically tying into storm management systems under or near the street.
Where Storm Drainage Starts: Roof Drains
The storm system begins at the roof. Roof drains collect water that lands on the roof and prevent it from pooling. Roof drainage performance is not accidental. Roof insulation and roof build-up are often designed with slope so water naturally moves toward roof drains rather than sitting in low spots.
- Roof slope: built into insulation or roof assembly
- Drain collection: roof drains capture and funnel water into piping
- Vertical conveyance: water is carried down through the building via storm piping
Following the Piping Down Through the Building
On the storm riser, you will typically see multiple roof drains at roof level connecting into piping of various diameters. Smaller branches may collect water from individual drains and then tie into larger piping as flows combine.
In the diagram, you may see a progression like:
- Multiple roof drains feeding into branch piping
- Branch piping increasing in size as flows combine
- Large vertical risers carrying water down through multiple floors
The Vertical Riser and the Building Exit
As storm piping combines, it often connects into a main vertical riser that carries water down through the building levels such as from the roof through upper floors, then down to the ground level. At the bottom, the system ties into a larger storm line that exits the building and connects to the storm management system under the street.
This is where the storm riser diagram is especially helpful: it shows the full vertical path from roof collection to final discharge connection, making it easier to understand how the system is intended to function as a whole.
Why These Risers Matter for Blueprint Reading
Gas and storm riser diagrams help you understand system intent in a way floor plans alone cannot. Floor plans show where piping travels in a given level. Risers show how the system is organized vertically and how it connects from service to endpoint.
- Gas riser diagrams clarify service entry, pressure control, pipe sizing, and how equipment is served.
- Storm riser diagrams clarify roof drain collection, vertical conveyance, and storm discharge routing.
With a solid grasp of these risers, it becomes much easier to interpret the broader plumbing set and understand why certain piping routes, sizes, and connections appear the way they do on the plans.
