1. What is a Tankless Water Heater Flow Rate Calculator?

Definition: This calculator determines the required flow rate for a tankless water heater by summing the flow rates of all simultaneously used fixtures.

Purpose: It helps homeowners and plumbers properly size a tankless water heater to meet 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 (GPM)

Explanation: The flow rates of all fixtures that might be used simultaneously are added together to determine the minimum required flow rate for the tankless water heater.

3. Importance of Proper Flow Rate Calculation

Details: Correct flow rate calculation ensures your tankless water heater can provide enough hot water when multiple fixtures are in use, preventing temperature fluctuations and insufficient heating.

4. Using the Calculator

Tips: Enter the flow rate (GPM) for each fixture that might be used simultaneously. Common fixture flow rates:

• Shower: 2.0-2.5 GPM
• Kitchen sink: 1.5-2.2 GPM
• Bathroom sink: 0.5-1.5 GPM
• Washing machine: 1.5-3.0 GPM
• Dishwasher: 1.0-2.5 GPM

5. Frequently Asked Questions (FAQ)

Q1: What if I have more than 3 fixtures?
A: Add their flow rates to one of the existing fields or modify the calculator to include more input fields.

Q2: How do I find my fixture's flow rate?
A: Check manufacturer specifications, look for the GPM rating on the fixture, or measure by timing how long it takes to fill a one-gallon container.

Q3: Should I include cold water fixtures?
A: No, only include fixtures that will use hot water from the tankless heater.

Q4: What about temperature rise considerations?
A: This calculator determines flow rate only. Temperature rise depends on your climate and the heater's BTU rating.

Q5: Should I add a safety margin?
A: It's recommended to add 10-20% to the calculated flow rate to account for variations in water pressure and future needs.