1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator determines the required flow rate (GPM) for a tankless water heater based on your household's peak water demand.

Purpose: Helps homeowners and plumbers select the appropriately sized tankless water heater to meet simultaneous hot water needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate (Gallons Per Minute)
• \( Q_i \) — Flow rate of individual fixtures

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

3. Importance of Proper Sizing

Details: Undersized heaters can't meet demand during peak usage, while oversized units waste energy and cost more upfront.

4. Using the Calculator

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

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

5. Frequently Asked Questions (FAQ)

Q1: What if I have low-flow fixtures?
A: Adjust the GPM values downward (e.g., 1.5 GPM for low-flow showerheads).

Q2: Should I consider future additions?
A: Yes, add 1-2 GPM if planning additional bathrooms or fixtures.

Q3: What about temperature rise?
A: This calculator determines flow rate only. Consider a separate BTU calculation for temperature requirements.

Q4: How many fixtures can run simultaneously?
A: A 7 GPM heater can typically run 2-3 fixtures (e.g., shower + sink).

Q5: What's better - gas or electric?
A: Gas heaters typically provide higher GPM (7-10) than electric (2-5).