Quick Answer
A standard pressure tank is not suitable for potable water due to the potential for contamination and bacterial growth inside the tank.
Pressure Tank Design for Potable Water
For potable water applications, a dedicated pressure tank specifically designed for water storage is required. These tanks have features such as a clean, food-grade interior and a seamless, welded construction to prevent contamination. A minimum 1.9 specific gravity (SG) tank is recommended to ensure the tank can hold air at the top and prevent water from leaking into the bladder.
Tank Sizing Calculations
When sizing a pressure tank for a potable water system, it’s essential to consider the maximum drawdown, which is the amount of water withdrawn from the tank before the pump kicks in. A general rule of thumb is to size the tank for 2-3 minutes of flow at the maximum rate, with a minimum of 10 gallons per minute (gpm) for a single-family home. For example, a home with a 1/2 horsepower pump drawing 10 gpm would require a tank with a minimum volume of 20-30 gallons.
Additional Considerations
In addition to tank design and sizing, other factors such as corrosion protection, tank material, and installation orientation should be considered to ensure a safe and reliable potable water system. A pressure tank designed for potable water should meet or exceed the standards set by the World Health Organization (WHO) or the American National Standards Institute (ANSI). It’s also essential to follow local regulations and codes for potable water systems.
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