How big should my water storage tank be?
Water storage tanks come is many different sizes, shapes colors and materials. Some people are looking for a small tank for emergency use while others may be looking for a large tank to meet household and irrigation demands. This post will help you understand some of the factors that need to be considered to determine the size of the storage tank. If you are wondering if you even need a storage tank, check out some of our other posts including Do I Need a Water Storage Tank? and Cost Considerations of Plastic tanks.
In general we recommend that water storage tanks should be sized large enough to meet local fire code requirements plus an additional 2 days of water supply for your irrigation and household needs. The average American household with water efficient appliances uses, on average 70 gallons per person per day. A family of 4 would use about 250 gallons per day on average. If you want to do a bit more precise calculation of your family’s water usage with landscaping, check out this handy water usage calculator!
Napa County requires rural homes that are not within reach of a city fire hydrant to have 2500 gallons of dedicated fire storage. New homes are required to have an additional ~800 gallons of water available for the fire sprinkler system. Right off the starting line a 3300 gallon tank is the minimum to build a new house in Napa County if you are outside of the city limits. This doesn’t account for any actual water use for the house or landscaping because you don’t want to be dipping into your dedicated fire supply!
With the above requirements in mind we recommend a 5000 gallons of water storage as a baseline, leaving 1700 gallons of water as a buffer for watering the yard and household uses. For large properties with significant landscaping and a large home we recommend a minimum of 10,000 gallons. For smaller properties and homes that don’t have to worry about fire considerations, 2500-3000 gallons is a common tank tank that will give you plenty of water for daily needs. Please contact us to discuss your particular situation and questions.
Tank material/construction considerations
Plastic (HDPE) storage tanks can be obtained in many sizes, but the best price points are for plastic tanks that are 2500 gallons, 3000 gallons and 5000 gallons because they can be transported via road without any special permits and can be installed very quickly. As long as the same size is chosen, multiple plastic tanks can be used to increase storage capacity by placing the tanks side by side. Installing storage tanks at different heights should be avoided as it can lead to increased system complexity and in some cases results in the tanks at higher elevations not being able to fill completely because the lower tanks overflow. In many counties, permits are not required to install a plastic storage tank and Napa County only requires permits for these tanks if they are over 5000 gallons. Check out Norwesco to see what sizes and dimensions are commonly available. When purchasing a plastic tank, do not purchase tanks that are made from white/clear plastic as they do not block the UV radiation and allow algae to grow in the tank and the plastic degrades very quickly. Blue, green, black and dark green plastic tanks are available that will easily last 20 years in the sun and algae will not grow in them! Oakville Pump Service can help you purchase and install the best HDPE tank for your application!
Cement tanks are also a good option but must be installed by a qualified contractor to ensure they do not develop cracks or have other failures. Cement tanks are commonly available in 5,000 and 10,000 gallon configurations and, while fire resistant, cost significantly more than the plastic alternative, require a permit to install and take much longer to install and commission than HDPE tanks. Cement takes are also permanent structures that cannot be moved and significant expenses can be expected in the future if plans change and the tank needs to be moved or removed altogether.
The classic look of the ranch style corrugated steel tanks are yet another option and are often chosen for their aesthetic value when the only location for the storage tank is in highly visible location . They can be customized as to height and diameter. Custom linings or coatings can be applied to minimize corrosion-the biggest drawback that metal tanks face. Because of the custom nature of steel tank construction, costs are much higher than their plastic alternatives as are lead times for installation.
If you’re considering a storage tank, please call one of our staff at (707) 944-2471 to discuss the type and size of storage tank that would best meet your needs! Our experienced project managers will make an appointment with you to review your water needs, the water supply available from your well or spring, help you find a suitable location for a storage tank to be installed and help you through the entire process of ensuring a reliable and adequate water supply in the Napa Valley.
If there are questions you’d like our blog to address, please contact us and we will try to address them for you in future blogs.