1. What is a Flow Rate Calculator for Tankless Water Heaters?

Definition: This calculator determines the required flow rate (in gallons per minute - GPM) for a tankless water heater based on your fixture usage.

Purpose: It helps homeowners and plumbers properly size a tankless water heater by calculating the total simultaneous hot water demand.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Total flow rate needed (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 minimum required flow rate for your tankless water heater.

3. Importance of Proper Flow Rate Calculation

Details: Correct flow rate calculation ensures your tankless water heater can meet your hot water demands without temperature fluctuations or inadequate supply.

4. Using the Calculator

Tips: Enter the flow rate for each fixture in GPM. Default values are provided based on typical fixture flow rates. All values must be ≥ 0.

5. Frequently Asked Questions (FAQ)

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

Q2: Should I include all fixtures in my home?
A: Only include fixtures that might run simultaneously. For example, if you never run the dishwasher while showering, you might exclude it.

Q3: What if my actual usage is lower than the calculation?
A: It's better to slightly oversize than undersize. A unit with 20% more capacity than your calculation is often recommended.

Q4: How does temperature rise affect this calculation?
A: This calculator determines flow rate needs. For temperature considerations, you'll also need to consider your groundwater temperature and desired output temperature.

Q5: Can I add more fixtures to this calculator?
A: Yes, you could expand it to include bathtubs (typically 4-6 GPM), outdoor faucets, or other water-using appliances.