When planning a water storage system, one of the first questions to answer is: How big should my water storage tank be?
Water storage tanks come in many sizes, shapes, colors, and materials, designed to meet a range of needs—from small emergency tanks to large-capacity tanks for household, agricultural, or irrigation use. This guide will help you understand how to choose the right tank size for your property.
In general, we recommend sizing your water storage tank to meet:
Local fire code requirements, and
At least two days of household and irrigation demand.
The average American household with water-efficient appliances uses about 70 gallons per person per day.
So, for a family of four, daily use averages 250–300 gallons.
If you want a more precise estimate that includes landscaping, try our Water Usage Calculator.
In Napa County, rural homes outside city fire hydrant reach must have:
2,500 gallons of dedicated fire protection storage, plus
~800 gallons for the fire sprinkler system in new homes.
That means a minimum of 3,300 gallons is required before accounting for household or irrigation use.
Because you don’t want to draw from your fire reserve, we typically recommend at least a 5,000-gallon water tank for new rural homes. This leaves about 1,700 gallons available for daily household and landscaping needs.
For larger properties or estates with extensive landscaping, 10,000 gallons or more is often ideal.
For smaller homes or properties without fire protection requirements, 2,500–3,000 gallons usually provides a comfortable buffer.
👉 Tip: Always confirm your local fire code and county requirements before choosing a tank size.
When deciding on the type of water storage tank, consider cost, installation requirements, durability, and aesthetics. Below are the most common options:
High-density polyethylene (HDPE) tanks are the most popular choice for residential and agricultural use.
They’re affordable, lightweight, and easy to install.
Best value sizes: 2,500, 3,000, and 5,000 gallons (transportable without permits).
Scalable: You can install multiple tanks side by side for greater capacity.
Installation note: Avoid setting tanks at different elevations—this can cause uneven filling and overflow issues.
Permits: In many counties, including Napa, permits are only required for tanks over 5,000 gallons.
Color choice: Avoid clear or white plastic tanks, as they promote algae growth and UV degradation.
Instead, choose blue, green, black, or dark green tanks, which can last 20+ years outdoors.
Check out Norwesco for available HDPE tank sizes and dimensions.
Oakville Pump Service can help you select and install the ideal plastic water tank for your property.
Concrete (cement) tanks are a durable and fire-resistant option, typically available in 5,000–10,000 gallon sizes.
Pros:
Fire-resistant and long-lasting
Great for permanent installations
Cons:
Higher cost
Requires a qualified contractor
Needs a permit and longer installation time than plastic tanks
For those who want a classic ranch-style aesthetic, corrugated steel tanks are a great option.
Can be customized in height and diameter
May include special linings or coatings to prevent corrosion
More expensive and have longer lead times due to their custom construction
If your tank will be in a highly visible location, a steel tank can enhance your property’s look while providing reliable water storage.
Choosing the right water storage tank size and material can be complex.
Our team at Great Northern Tanks is here to help you every step of the way.
📞 Call us at (707) 944-2471 to schedule a consultation.
We’ll help you:
Evaluate your household and irrigation water needs
Assess your well or spring supply
Find the best location for installation
Ensure compliance with Napa County water storage and fire safety requirements
If you have questions or topics you’d like us to cover in future blog posts, contact us today — we’d love to hear from you!
