1. What is a Tankless Water Heater GPM Calculator?

Definition: This calculator estimates the required flow rate (in gallons per minute) for a tankless water heater based on your household's fixture usage.

Purpose: Helps homeowners and plumbers properly size a tankless water heater to meet simultaneous hot water demands.

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 total demand.

3. Importance of Proper Sizing

Details: Undersized tankless heaters can't meet demand, while oversized units waste energy. Proper GPM calculation ensures consistent hot water supply.

4. Using the Calculator

Tips: Enter the number of each type of fixture in your home. The calculator uses standard flow rates (adjustable if needed).

5. Frequently Asked Questions (FAQ)

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

Q2: Should I consider simultaneous use?
A: Yes, calculate for the maximum number of fixtures likely to be used at the same time.

Q3: What about low-flow fixtures?
A: For low-flow showers (1.5-2.0 GPM) or faucets (0.5-1.0 GPM), adjust the default values accordingly.

Q4: How does temperature rise affect this?
A: This calculates flow rate only. For winter sizing, consider a separate temperature rise calculation.

Q5: Should I add a safety margin?
A: Adding 10-20% to the calculated GPM is recommended for peak demand periods.