Gas Station Underground Fuel Piping: Pipe Size, Layout and Installation Guide
News 2026年 8月 15日 23
Introduction
Gas Station Underground fuel piping is a critical part of a gas station fuel delivery system.
It connects the underground storage tank and submersible oil pump to the fuel dispensers and must provide reliable fuel delivery while reducing leakage and environmental risks.
For gas station projects in China, GB 50156-2021 specifies requirements for underground process piping, including pipe materials, burial depth, installation method, double-wall piping and leak detection.
This guide explains the key requirements and practical considerations for selecting and installing underground fuel piping.
Note: Requirements vary by country and project. The information below is for engineering reference. Actual projects should comply with local codes, approved designs and installation requirements.
1. What Is Underground Fuel Piping?
The underground fuel piping system transfers fuel from the underground storage tank to the fuel dispenser.
A typical system includes:
Underground Fuel Tank → submersible oil pump → Main Fuel Pipe → Branch Pipes → Fuel Dispenser
Depending on the station design, the underground system may also include:
- Fuel filling pipes
- Fuel dispensing pipes
- Vapor recovery pipes
- Tank vent pipes
- Leak detection systems
- Double-wall piping systems
The pipe layout should be designed together with the submersible oil pump, fuel dispenser and underground tank rather than treated as an independent component.
2. Should Gas Station Fuel Pipes Be Single-Wall or Double-Wall?
For underground fuel dispensing pipelines, GB 50156-2021 requires the use of double-wall piping.
The standard specifies that:
- The inner pipe must comply with the relevant requirements for fuel process piping.
- Double-wall non-metallic piping must have an outer layer resistant to fuel, corrosion and aging and meet system pressure testing requirements.
- For double-wall steel piping, the outer pipe wall thickness should be at least 5 mm.
- The space between the inner and outer pipes should be continuous.
- The lowest point of the double-wall system should have a leak detection point.
- The piping should slope toward the leak detection point at not less than 5‰.
- Online leak monitoring is recommended for the piping system.
Why Is Double-Wall Piping Important?
A double-wall pipe provides an additional containment layer.
If the inner pipe develops a leak, the space between the two layers can help direct the leaked fuel toward the detection point.
This makes leakage easier to detect and helps reduce the risk of fuel entering surrounding soil.
3. What Pipe Materials Are Used?
GB 50156-2021 allows different piping materials depending on the application.
For process piping, the standard includes:
- Seamless steel pipes
- Suitable thermoplastic piping for fuel service
For seamless steel pipes, the nominal wall thickness should be at least 4 mm, and buried steel pipe connections should use welding.
For thermoplastic piping, the main structural layer should use suitable polyethylene material, with a wall thickness of at least 4 mm. Buried thermoplastic piping should use compatible electrofusion fittings.
The actual pipe material should be selected according to:
- Fuel type
- Pipe installation method
- Operating pressure
- Temperature
- Corrosion environment
- Local regulations
- Manufacturer specifications
4. How Do You Choose the Fuel Pipe Diameter?
There is no single pipe diameter that is suitable for every gas station.
Pipe diameter should be determined based on the complete fuel delivery system.
Important parameters include:
| Parameter | Why It Matters |
|---|
| Fuel flow rate | Determines required fuel capacity |
| Number of dispensers | Affects total demand |
| Number of nozzles | Affects simultaneous fueling demand |
| Pipe length | Longer pipes generally create more pressure loss |
| Number of elbows | Additional fittings increase resistance |
| Elevation difference | Affects required pump head |
| Pump performance | Must match the piping system |
A simplified engineering relationship is:
Required Pump Head = Static Head + Pipe Friction Loss + Fitting Loss + Required Outlet Pressure
Therefore, selecting a larger pump without checking the pipeline can result in an improperly matched system.
For more information, see our submersible oil pump Selection Guide.
5. One submersible oil pump Can Supply Multiple Dispensers
A common gas station configuration uses one submersible oil pump to supply several fuel dispensers.
A typical layout is:
Underground Tank
↓
submersible oil pump
↓
Main Fuel Pipeline
↓
Branch Pipelines
↓
Multiple Fuel Dispensers
The actual number of dispensers and nozzles supplied by one pump depends on:
- Required flow rate
- Simultaneous fueling demand
- Pump capacity
- Pipeline diameter
- Pipeline length
- Pressure loss
- Fuel dispenser requirements
Therefore, “one pump can supply three dispensers” should not be treated as a universal rule.
The pump and pipeline should be selected as one complete system.
6. How Deep Should Underground Fuel Pipes Be Buried?
GB 50156-2021 specifies that the burial depth of underground process piping should be not less than 0.4 m.
For piping installed beneath concrete areas or roads, the top of the pipe should be at least 0.2 m below the underside of the concrete layer.
The area around the pipe should be backfilled with at least 100 mm of neutral sand or fine soil.
Quick Reference
| Requirement | Reference Value |
|---|
| Minimum burial depth of underground process piping | ≥ 0.4 m |
| Pipe top below underside of concrete layer | ≥ 0.2 m |
| Sand/fine soil around pipe | ≥ 100 mm |
These values are different from underground tank burial requirements.
Pipe burial depth should not be confused with fuel tank burial depth.
For more information about underground tank installation and burial requirements, see our [Underground Fuel Tank Installation Guide].
7. Does Underground Fuel Piping Need a Slope?
Yes, but the required slope depends on the type of pipeline.
GB 50156-2021 specifies:
Fuel unloading pipe
Minimum slope:
2‰
Vapor recovery and tank vent horizontal pipes
Minimum slope:
1%
These pipelines should generally slope toward the underground tank.
For double-wall fuel dispensing piping, the standard requires the system to slope toward the leak detection point at not less than 5‰.
This means different pipelines in a gas station should not automatically use the same slope.
8. Why Does Pipe Length Affect Pump Selection?
Pipe length directly affects the resistance of the fuel delivery system.
As the pipeline becomes longer, friction loss generally increases.
For example:
Short Pipeline
→ Lower friction loss
→ Lower required pump head
Long Pipeline
→ Higher friction loss
→ Higher required pump head
Pipe diameter also matters.
A smaller pipe can increase flow velocity and friction loss, while a larger pipe can reduce pressure loss but may increase installation cost.
Therefore, when selecting a submersible oil pump, provide the supplier with:
- Tank location
- Dispenser location
- Pipeline length
- Pipe diameter
- Number of bends
- Elevation difference
- Required fuel flow
This information allows the pump to be matched more accurately to the actual project.
9. Common Underground Fuel Piping Layout
A typical system can be understood as:
Storage Tank
↓
submersible oil pump
↓
Main Fuel Pipeline
↓
Branch Pipeline
↓
Fuel Dispenser
The tank manhole provides access to important underground equipment such as the submersible oil pump, piping connections, liquid level monitoring equipment and leak detection components.
Learn more about [Gas Station Tank Manhole Structure and Installation].
At the same time, separate systems may include:
Fuel Filling Pipe → Underground Tank
Vapor Recovery Pipe → Underground Tank
Tank Vent Pipe → Vent System
Double-Wall Pipe → Leak Detection System
Keeping these systems clearly separated during design helps simplify installation, maintenance and inspection.
10. Common Underground Fuel Piping Problems
Problem 1: Choosing Pipe Diameter Only by Dispenser Quantity
Two stations may have the same number of dispensers but different pipeline lengths and layouts.
Better approach: Consider flow rate, pipe length, fittings and pressure loss together.
Problem 2: Treating All Underground Pipes as Having the Same Slope
Fuel pipes, vapor recovery pipes and double-wall piping have different design requirements.
Better approach: Determine the slope according to the function of each pipeline.
Problem 3: Ignoring Leak Detection
A buried pipeline is difficult to inspect visually after installation.
Better approach: Use a properly designed double-wall piping system with an appropriate leak detection point and monitoring system.
Problem 4: Selecting the Pump Before Designing the Pipeline
A high-flow pump does not automatically solve a poorly designed piping system.
Better approach:
Tank → Pump → Pipeline → Dispenser
should be evaluated as one system.
11. Underground Fuel Piping Selection Checklist
Before ordering or designing the piping system, confirm:
| Project Parameter | Required Information |
|---|
| Fuel type | Gasoline / Diesel |
| Tank capacity | m³ |
| Number of dispensers | Units |
| Number of nozzles | Units |
| Required flow rate | L/min |
| Main pipe diameter | Project-specific |
| Branch pipe diameter | Project-specific |
| Pipeline length | m |
| Elevation difference | m |
| Number of bends | pcs |
| Pipe material | Steel / Thermoplastic |
| Double-wall requirement | Yes / No according to project |
| Leak detection | Required |
| Pump flow and head | L/min + m |
Providing these parameters to the equipment supplier can significantly improve the accuracy of pump and piping selection.
12. Conclusion
Underground fuel piping is more than a connection between the fuel tank and dispenser.
A reliable system requires the correct combination of:
- Pipe material
- Pipe diameter
- Pipeline length
- Burial depth
- Slope
- Double-wall protection
- Leak detection
- submersible oil pump performance
According to GB 50156-2021, underground process piping should have a minimum burial depth of 0.4 m, while piping beneath concrete areas or roads should maintain at least 0.2 m between the pipe top and the underside of the concrete layer. Double-wall underground fuel dispensing piping is also required, with specific requirements for leak detection and slope.
For a complete gas station project, pump selection and pipeline design should be evaluated together rather than separately.
Need Help Selecting Fuel Piping or a submersible oil pump?
Send us your:
- Tank capacity
- Number of dispensers
- Required flow rate
- Pipeline length
- Pipe diameter
- Fuel type
- Voltage
Our team can help evaluate the appropriate equipment configuration for your project.
