1. What is GPM for Tankless Water Heaters?

Definition: GPM (Gallons Per Minute) measures the flow rate a tankless water heater must deliver to meet simultaneous hot water demands.

Purpose: This calculator helps determine the minimum flow rate capacity needed for a tankless water heater based on your household's fixtures.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The calculator sums the GPM requirements of all fixtures that might be used at the same time to determine the minimum tankless heater capacity needed.

3. Importance of Proper GPM Calculation

Details: Undersizing leads to insufficient hot water during peak demand, while oversizing increases energy costs. Proper calculation ensures comfortable and efficient operation.

4. Using the Calculator

Tips: Enter the number of each fixture type that might run simultaneously. The calculator uses standard GPM values:

• Shower: 2.5 GPM
• Sink: 1.5 GPM
• Dishwasher: 2.0 GPM
• Washing Machine: 2.5 GPM
• Bathtub: 4.0 GPM

5. Frequently Asked Questions (FAQ)

Q1: What if my fixtures have different flow rates?
A: Use our Advanced Tankless Calculator that allows custom GPM inputs for each fixture.

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

Q3: What about low-flow fixtures?
A: Low-flow showerheads (1.5-2.0 GPM) and faucets (0.5-1.0 GPM) will reduce total GPM needs.

Q4: How does temperature rise affect GPM?
A: Higher temperature rises reduce the effective GPM capacity. Consider both flow rate and temperature requirements.

Q5: Should I add a safety margin?
A: It's recommended to add 10-20% to the calculated GPM for unexpected demand spikes.