Determining the Correct Pipe Size for a 1 HP Submersible Pump at Borehole and Height

When designing a water delivery system, determining the appropriate pipe size is crucial to ensure efficient and reliable water flow. This article will guide you through the steps to calculate the required pipe size for a 1 HP submersible pump located at a borehole depth of 70 feet and a height of 250 feet.

Step 1: Total Dynamic Head (TDH) Calculation

To calculate the Total Dynamic Head (TDH), we need to sum the static lift and dynamic lift, and consider friction losses. In this scenario, the static lift is the vertical distance the water needs to be lifted, which is 250 feet. The dynamic lift will be disregarded for simplicity since it requires more detailed information on the pipe length and fittings.

Total Dynamic Head (TDH) Calculation:

TDH Static Lift Dynamic Lift - Friction Loss

Assuming a direct lift without friction losses:

TDH 250 feet - 70 feet 320 feet

Step 2: Determining Flow Rate

A 1 HP submersible pump typically delivers around 5 to 10 gallons per minute (GPM) depending on the pump's efficiency and system setup. For this example, we will assume a flow rate of 10 GPM.

Step 3: Determine Pipe Size

To find the appropriate pipe size, we need to consider the velocity of the water in the pipe. A common recommendation is to maintain a water velocity between 3 to 5 feet per second (fps) to minimize friction loss and maintain efficiency.

Calculate Required Pipe Diameter

1. Calculate the required flow area:

Using the formula for flow rate:

Q A v

Where:

Q flow rate in cubic feet per second

A cross-sectional area of the pipe in square feet

v velocity in feet per second

2. Convert GPM to cubic feet per second:

10 GPM 10 / 7.48 cubic feet per minute ≈ 1.34 cubic feet per minute

(1.34 / 60) ≈ 0.0223 cubic feet per second

Assuming a velocity of 4 fps:

Rearranging the formula to solve for area A:

A Q / v 0.0223 cubic feet per second / 4 fps ≈ 0.005575 square feet

3. Calculate the diameter:

Using the area of a circle:

A π middot; (D / 2)2

D 2 middot; √(A / π) ≈ 2 middot; √(0.005575 / π) ≈ 0.084 feet ≈ 1.01 inches

Conclusion:

Based on these calculations, a 1-inch diameter pipe would be sufficient to deliver water from the pump at the specified conditions. However, it is advisable to consult with a plumbing engineer to consider friction losses, fittings, and other factors that could affect performance, potentially requiring a larger pipe size if necessary.

Additional Considerations:

Friction Loss: Friction loss is an important factor in water delivery systems. As water travels through the pipe, it experiences resistance, which decreases the flow rate and increases pressure drop. A detailed analysis of the total dynamic head, considering the entire length and fittings, can help in optimizing the system. Flow Rate Adjustments: Factors such as the pump’s efficiency, system setup, and the desired pressure can affect the final flow rate. Regularly reviewing the system and making adjustments as needed can ensure consistent performance. Engineering Expertise: A professional plumbing engineer can provide a more comprehensive analysis, taking into account all variables and ensuring the system is designed for maximum efficiency and reliability.