1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator estimates the required flow rate (GPM) for a tankless water heater by summing the flow rates of simultaneously used fixtures.

Purpose: Helps homeowners and plumbers select an appropriately sized tankless water heater for their needs.

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 (GPM)

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 heaters can't meet demand, while oversized units waste energy. Proper sizing ensures consistent hot water supply and energy efficiency.

4. Using the Calculator

Tips: Enter the flow rates for all fixtures that might be used simultaneously. Default values are provided for common fixtures.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical shower flow rate?
A: Standard showerheads use 2.5 GPM, while low-flow models use 1.5-2.0 GPM.

Q2: Should I include all fixtures in my home?
A: Only include fixtures that might run simultaneously (e.g., shower + sink).

Q3: What if my total exceeds 10 GPM?
A: Consider installing multiple tankless units or a whole-house system.

Q4: Does this account for temperature rise?
A: No, this calculates flow rate only. Temperature requirements affect BTU needs.

Q5: What about fixture probability of simultaneous use?
A: This calculator assumes worst-case simultaneous use for conservative sizing.