1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator determines the required flow rate (Gallons Per Minute) for a tankless water heater based on simultaneous fixture usage.

Purpose: It helps homeowners and plumbers properly size tankless water heaters by calculating peak hot water demand.

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

Explanation: The calculator sums the flow rates of all fixtures that might be used simultaneously to determine the peak demand.

3. Importance of Proper GPM Calculation

Details: Undersized tankless heaters can't meet demand during peak usage, while oversized units waste energy. Accurate GPM calculation ensures optimal performance and efficiency.

4. Using the Calculator

Tips: Enter the number of each type of fixture that might run simultaneously. Default flow rates are provided but can be adjusted if you know your specific fixture rates.

5. Frequently Asked Questions (FAQ)

Q1: What are typical flow rates for fixtures?
A: Showers: 2.5 GPM, Sinks: 1.5 GPM, Dishwashers: 1.0 GPM, Washing Machines: 2.0 GPM.

Q2: Should I count all fixtures in my home?
A: No, only count fixtures that might run simultaneously during peak usage times.

Q3: What if my fixtures have different flow rates?
A: Use the "Other Fixtures" field to add custom flow rates or adjust the default values.

Q4: How much extra capacity should I add?
A: Add 10-20% to the calculated GPM for safety margin and future needs.

Q5: Does this account for temperature rise?
A: No, this calculates flow rate only. Temperature rise depends on incoming water temperature and heater specifications.