1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator determines the total hot water demand (in GPM) and recommends an appropriately sized tankless water heater.

Purpose: Helps homeowners and plumbers select a tankless water heater that can meet peak 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

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

3. Importance of Proper Sizing

Details: Undersized tankless heaters can't meet demand, while oversized units waste energy. Proper sizing ensures continuous hot water and energy efficiency.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What's the typical GPM of a residential tankless heater?
A: Electric: 2-5 GPM, Gas: 5-10 GPM. Commercial units can go higher.

Q2: Should I add all fixtures or just those used together?
A: Only include fixtures that might run simultaneously during peak usage.

Q3: What if my total exceeds 10 GPM?
A: Consider multiple tankless units in parallel or a commercial-grade unit.

Q4: How do I find my fixtures' GPM?
A: Check manufacturer specs or look for flow restrictors (often marked with GPM).

Q5: Does temperature rise affect this calculation?
A: Yes, GPM ratings assume a specific temperature rise (typically 70°F). Colder incoming water may reduce effective capacity.