1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator determines the total flow rate (GPM) required for a gas tankless water heater based on fixture flow rates.

Purpose: It helps homeowners and plumbers properly size a tankless water heater by calculating the simultaneous hot water demand.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate (Gallons Per Minute)
• \( Q_i \) — Flow rate of each individual fixture (GPM)

Explanation: The calculator sums the flow rates of all fixtures that might be used simultaneously to determine the required capacity of the tankless water heater.

3. Importance of Proper GPM Calculation

Details: Correct GPM calculation ensures your tankless water heater can meet peak demand without temperature fluctuations or insufficient flow.

4. Using the Calculator

Tips: Enter the flow rate for each fixture (default values provided). Consider all fixtures that might run simultaneously.

5. Frequently Asked Questions (FAQ)

Q1: What if I have more than one of each fixture?
A: Multiply each fixture's GPM by the number of units (e.g., 2 showers = 2 × 2.5 GPM).

Q2: What's the typical flow rate for fixtures?
A: Standard rates are 1.5 GPM for kitchen sink, 0.75 GPM for bathroom sink, 2.5 GPM for shower, and 4.0 GPM for bathtub.

Q3: Should I include all fixtures in my home?
A: Only include fixtures that might run simultaneously during peak usage times.

Q4: How does this affect tankless water heater sizing?
A: Choose a unit with a GPM rating that meets or exceeds your calculated total.

Q5: What about temperature rise considerations?
A: This calculator determines flow rate only. For complete sizing, consider both flow rate and required temperature increase.