1. What is GPM Calculation?

GPM (Gallons Per Minute) calculation determines the total flow rate required for a Rinnai tankless water heater by summing the flow rates of all fixtures that may be used simultaneously.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Shower Flow Rate — Typical range: 1.5-2.5 gpm
• Faucet Flow Rate — Typical range: 0.5-2.2 gpm
• Dishwasher Flow Rate — Typical range: 1.0-2.5 gpm
• Washing Machine Flow Rate — Typical range: 1.5-3.0 gpm

Explanation: The calculator sums the flow rates of all fixtures to determine the total GPM requirement for proper tankless water heater sizing.

3. Importance of GPM Calculation

Details: Accurate GPM calculation ensures your Rinnai tankless water heater is properly sized to meet your household's hot water demands, preventing insufficient hot water supply.

4. Using the Calculator

Tips: Enter the flow rates for each fixture in gallons per minute (gpm). Use manufacturer specifications or standard values for accurate calculations.

5. Frequently Asked Questions (FAQ)

Q1: Why is GPM important for tankless water heaters?
A: GPM determines the heating capacity needed. Undersized units won't provide enough hot water for simultaneous use.

Q2: What is a typical GPM requirement for a household?
A: Most households require 5-7 GPM, but this varies based on the number of bathrooms and appliances.

Q3: Can I reduce my GPM requirement?
A: Yes, by using low-flow fixtures and staggering hot water usage.

Q4: What temperature rise should I consider?
A: Most calculations assume a 70°F temperature rise, but this depends on your groundwater temperature.

Q5: Should I consult a professional for sizing?
A: Yes, professional consultation is recommended for accurate sizing, especially for larger homes.