1. What is a Gas Tankless Water Heater Sizing Calculator?

Definition: This calculator estimates the required flow rate (GPM) for a gas tankless water heater based on the sum of all fixture flow rates in your home.

Purpose: It helps homeowners and plumbers properly size a tankless water heater to meet household hot water demands.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The calculator sums the flow rates of all fixtures that might run simultaneously to determine the minimum required GPM rating for your tankless water heater.

3. Importance of Proper Sizing

Details: Correct sizing ensures adequate hot water supply, prevents temperature fluctuations, and maximizes energy efficiency of your tankless water heater.

4. Using the Calculator

Tips: Enter the flow rate for each fixture in your home. Default values are provided based on typical flow rates. All values must be ≥ 0.

5. Frequently Asked Questions (FAQ)

Q1: What if I don't know my fixture flow rates?
A: Use the default values which represent typical flow rates for standard fixtures.

Q2: Should I include all fixtures in my home?
A: Only include fixtures that might run simultaneously. For example, two showers running at the same time.

Q3: What's the typical flow rate for a shower?
A: Standard showerheads have a flow rate of 2.5 GPM, while low-flow models may be 1.5-2.0 GPM.

Q4: How do I account for temperature rise?
A: This calculator determines flow rate only. For complete sizing, consider the temperature rise needed based on your climate.

Q5: Should I add a safety factor?
A: It's recommended to add 10-20% to the calculated GPM to account for future needs or occasional high demand.