1. What is a Tankless Hot Water Heater GPM Calculator?

Definition: This calculator estimates the total flow rate (in gallons per minute) required for a tankless water heater based on your fixture usage.

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate required (GPM)
• \( Q_i \) — 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 total GPM requirement.

3. Importance of Proper GPM Calculation

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

4. Using the Calculator

Tips: Enter the flow rates for each fixture you might use simultaneously. Default values represent typical flow rates:

• Shower: 2.5 GPM
• Sink: 1.5 GPM
• Dishwasher: 1.0 GPM
• Washing Machine: 2.0 GPM

5. Frequently Asked Questions (FAQ)

Q1: What if I have multiple showers?
A: Add each shower's GPM to the calculation (e.g., two showers would be 5.0 GPM total).

Q2: How do I find my fixture's GPM?
A: Check manufacturer specs or look for flow restrictor ratings (often printed on aerators).

Q3: Should I include cold water fixtures?
A: No, only include fixtures that will use hot water from the tankless heater.

Q4: What about temperature rise considerations?
A: This calculator determines flow rate only. Temperature rise depends on your climate and heater specs.

Q5: Do I need to account for future additions?
A: Yes, consider potential future fixtures when sizing your system.