By SCWS Team
February 1, 2026 · 14 min read
Your well produces only 2 gallons per minute—but your family needs 20 GPM during peak times. This math problem stumps many well owners, but there's an elegant solution: water storage. A properly sized tank turns your slow-producing well into a reliable water system, ensuring you never run dry during showers, laundry, or irrigation.
Whether you're dealing with a low-yield well, need fire protection capacity to meet county requirements, or want backup supply during power outages, adding storage is often the smartest investment you can make. In this comprehensive guide, we'll cover everything from tank types and sizing to costs and San Diego County fire requirements.
Why Add a Water Storage Tank to Your Well System?
Not every well needs a storage tank—but many would benefit from one. Here are the most common reasons homeowners invest in well water storage:
1. Low-Yield Well Compensation
If your well produces only 1-3 gallons per minute (GPM), it can't keep up with peak household demand like showers, laundry, and irrigation running simultaneously. A storage tank acts as a buffer—your slow well fills it 24/7, then a booster pump delivers high flow rates when needed. This is often the most cost-effective solution for wells that run dry during heavy use. Learn more in our guide on what to do when your well runs dry.
2. Fire Protection Requirements
San Diego County and other fire-prone areas often require dedicated fire water storage tanks for properties in high fire severity zones. These requirements ensure firefighters have adequate water supply when they need it most. Fire storage requirements range from 2,500 to 10,000 gallons depending on your location and property characteristics.
3. Backup Water Supply
Power outages stop your well pump—but stored water keeps flowing. A storage tank with a gravity-fed or battery-backed system provides water during emergencies. For properties dependent on well water, this peace of mind is invaluable. Our drought protection guide covers additional strategies for water security.
4. Agricultural and Irrigation Needs
Orchards, vineyards, and livestock require large volumes of water that most residential wells can't provide on-demand. Storage tanks allow you to accumulate water over time and deliver it when needed. See our agricultural well guide for specific considerations.
Types of Water Storage Tanks
The right tank material depends on your budget, installation type (above or below ground), and specific needs. Here's a comparison of the four main options:
Polyethylene (Plastic) Tanks
The most popular choice for residential water tanks for wells. These tanks are lightweight, affordable, and resistant to corrosion. Food-grade polyethylene is NSF-approved for potable water storage.
- Pros: Low cost, lightweight, corrosion-proof, UV-stabilized options available, easy to install
- Cons: 15-20 year lifespan (shorter than other materials), can become brittle in extreme sun, may crack if empty in freezing temps
- Best for: Above-ground residential installations, budget-conscious buyers
- Cost: $0.50-$1.50 per gallon
Fiberglass Tanks
Fiberglass tanks offer excellent durability and can be installed above or below ground. They won't rust or corrode and maintain structural integrity for decades.
- Pros: 30-40 year lifespan, rust-proof, lightweight for transport, suitable for underground use
- Cons: Higher cost than poly, can crack if improperly supported, requires professional installation for underground
- Best for: Underground installations, long-term investment properties
- Cost: $1.50-$3.00 per gallon
Concrete Tanks
The most durable option for large-volume or underground storage. Concrete tanks are typically poured on-site or delivered as pre-cast sections.
- Pros: 50+ year lifespan, excellent for underground, naturally cool water storage, fire-resistant
- Cons: Highest installation cost, requires professional installation, difficult to repair if cracked, can affect water pH
- Best for: Large agricultural systems, underground fire storage, permanent installations
- Cost: $3.00-$6.00 per gallon installed
Steel Tanks
Steel tanks offer high strength and are common in agricultural and fire protection applications. They require interior coating or galvanization to prevent rust.
- Pros: Strong and durable, repairable, available in very large sizes, fire-resistant
- Cons: Corrosion risk without proper coating, heavier than other options, requires periodic inspection and maintenance
- Best for: Fire protection storage, large-volume needs, agricultural applications
- Cost: $2.00-$4.00 per gallon
| Tank Type | Cost/Gallon | Lifespan | Underground? | Fire Approved? |
|---|---|---|---|---|
| Polyethylene | $0.50-$1.50 | 15-20 years | No* | Yes |
| Fiberglass | $1.50-$3.00 | 30-40 years | Yes | Yes |
| Concrete | $3.00-$6.00 | 50+ years | Yes | Yes |
| Steel | $2.00-$4.00 | 25-40 years | No | Yes |
*Some specialized ribbed poly tanks are rated for underground burial with proper bedding.
Sizing Your Water Storage Tank
Proper sizing ensures you have enough water when you need it without wasting money on unnecessary capacity. Consider these factors:
Household Water Needs
The average person uses 50-100 gallons per day for drinking, cooking, bathing, and household tasks. Here's a sizing guide based on household size and desired backup duration:
Residential Tank Sizing Guide
- 1-2 people, 1-day backup: 200-500 gallons
- 2-4 people, 3-day backup: 1,000-1,500 gallons
- 4-6 people, 5-day backup: 2,000-2,500 gallons
- Large family, 7-day backup: 3,000-5,000 gallons
Low-Yield Well Compensation
For wells that produce less than your peak demand, size your tank to hold at least 24 hours of normal household usage. This allows the well to continuously refill the tank, even during high-use periods. Formula:
Minimum Tank Size = Daily Usage - (Well GPM × 1,440 minutes)
Example: If your family uses 400 gallons/day and your well produces 0.25 GPM (360 gallons/day), you need at least 500-gallon storage to cover the deficit with buffer.
Fire Protection Requirements
Fire districts calculate required storage based on flow rate (typically 500-1,500 GPM) and duration (usually 20-30 minutes). Common requirements:
- Standard residential: 2,500-5,000 gallons
- Large homes (3,000+ sq ft): 5,000-7,500 gallons
- Remote properties/high fire risk: 7,500-10,000+ gallons
- Agricultural/commercial: 10,000-50,000+ gallons
Above Ground vs. Underground Installation
Your installation choice affects cost, maintenance, and aesthetics. Here's what to consider:
Above Ground Advantages
- ✓ 40-60% lower installation cost
- ✓ Easy visual inspection
- ✓ Simple maintenance and repairs
- ✓ No excavation required
- ✓ Can be relocated if needed
- ✓ Gravity feed possible with elevation
Underground Advantages
- ✓ Saves valuable yard space
- ✓ Naturally cooler water temperature
- ✓ Protected from sun and weather
- ✓ More aesthetically pleasing
- ✓ No freezing concerns
- ✓ Often required by HOAs
For most San Diego County installations, we recommend above-ground polyethylene or steel tanks. Freezing is rarely a concern, installation costs are lower, and maintenance is straightforward. Underground makes sense when space is limited or aesthetics are critical.
Water Storage Tank Costs
Your total investment includes the tank itself plus installation, pumps, plumbing, and electrical work. Here's what to budget:
| Tank Size | Poly Tank Cost | Fiberglass Cost | Steel Cost |
|---|---|---|---|
| 500 gallon | $250-$750 | $750-$1,500 | $1,000-$2,000 |
| 1,000 gallon | $500-$1,500 | $1,500-$3,000 | $2,000-$4,000 |
| 2,500 gallon | $1,250-$3,750 | $3,750-$7,500 | $5,000-$10,000 |
| 5,000 gallon | $2,500-$7,500 | $7,500-$15,000 | $10,000-$20,000 |
| 10,000 gallon | $5,000-$15,000 | $15,000-$30,000 | $20,000-$40,000 |
Installation Costs
- Site preparation (above ground): $200-$1,000
- Excavation (underground): $2,000-$8,000
- Booster pump system: $800-$2,500
- Plumbing connections: $500-$1,500
- Electrical work: $300-$1,000
- Fire department connection: $500-$1,500
- Permits: $200-$800
Total project cost for a typical 2,500-gallon above-ground poly tank with booster pump: $4,000-$8,000 installed.
Pump Configurations with Storage Tanks
Adding a storage tank to your well system typically requires a two-pump configuration:
Well Pump to Tank
Your existing well pump (or a new submersible pump) fills the storage tank. A float switch or level sensor controls operation—the pump runs when water drops below a set level and stops when full. For low-yield wells, this pump may run frequently at low GPM to keep up with the well's production rate.
Booster Pump to House
A booster pump (or transfer pump) draws water from the storage tank and delivers it to your home's pressure tank and plumbing. This pump is sized for your home's demand—typically 10-20 GPM for residential use—regardless of your well's actual production rate. Common configurations include:
- Jet pump: Good for shallow tanks, moderate pressure needs
- Submersible booster: Ideal for underground tanks
- Variable speed pump: Energy-efficient, consistent pressure
- Constant pressure system: Best performance, higher cost
For pump selection guidance, see our article on types of well pumps.
Maintenance and Cleaning
Regular maintenance extends tank life and keeps your water safe:
Annual Inspection Checklist
- Check tank exterior for cracks, rust, or damage
- Inspect fittings and connections for leaks
- Test float switches and level sensors
- Verify overflow drain is clear
- Check screens and filters
- Inspect roof/cover for damage and debris
Tank Cleaning (Every 1-3 Years)
Even potable water tanks accumulate sediment and biofilm over time. Professional cleaning involves:
- Draining the tank completely
- Entering the tank (for large tanks) or using specialized tools
- Scrubbing interior surfaces
- Removing sediment from the bottom
- Sanitizing with chlorine solution (50-100 ppm)
- Rinsing thoroughly until chlorine is below 4 ppm
- Refilling and testing water quality
Professional cleaning costs: $200-$500 depending on tank size and accessibility.
For more on keeping your well water safe, see our water testing guide and bacteria treatment guide.
San Diego County Fire Water Storage Requirements
If you're building in a high fire severity zone, you'll likely need dedicated fire water storage. Requirements vary by fire district, but here's what to expect:
Typical San Diego County Fire Storage Requirements
- Minimum capacity: 2,500-5,000 gallons for most residential
- Fire department connection: 2.5" NST female coupling, accessible
- Tank color: Must be visible (often red or light-colored)
- Dedicated capacity: Fire storage cannot be counted as household supply
- Access road: Fire apparatus must be able to reach the tank
- Signage: "Fire Water" marking required
Always contact your local fire district before purchasing a tank. Requirements vary significantly between districts and can depend on:
- Distance from fire station
- Building square footage
- Property location and terrain
- Proximity to fire hydrants
- Type of construction (sprinklered vs. non-sprinklered)
For permit information, see our San Diego well permit guide.
Frequently Asked Questions
What size water storage tank do I need for my well?
For household use, plan for 50-100 gallons per person per day. A family of four typically needs a 1,000-2,500 gallon tank for 3-7 days of backup supply. If you have a low-yield well, size your tank to hold at least 24 hours of household demand so the well can slowly refill it overnight. Fire protection requirements in San Diego County typically require 2,500-10,000 gallons depending on your fire district.
How much does a water storage tank cost?
Polyethylene tanks cost $0.50-$1.50 per gallon ($500-$3,000 for 1,000-2,500 gallons). Fiberglass costs $1.50-$3.00 per gallon. Steel tanks run $2-$4 per gallon. Concrete tanks cost $3-$6 per gallon installed. Add $1,000-$5,000 for professional installation including pump configuration, plumbing, and electrical work.
Should I install my water storage tank above ground or underground?
Above-ground tanks cost 40-60% less to install and are easier to maintain and inspect. Underground tanks save space, keep water cooler, and are more aesthetically pleasing. Choose underground if you have freeze concerns (rare in San Diego), limited space, or HOA restrictions. Most residential installations in Southern California use above-ground polyethylene tanks for cost-effectiveness.
What are San Diego County fire water storage requirements?
San Diego County fire districts typically require 2,500-10,000 gallons of dedicated fire water storage for properties in high fire severity zones. Requirements vary by fire district, property size, distance from fire hydrants, and building square footage. The tank must have a fire department connection, be painted a visible color, and maintain the required capacity at all times. Contact your local fire district for specific requirements.
How often should I clean my water storage tank?
Clean and inspect your water storage tank every 1-3 years depending on water quality. Signs you need cleaning sooner include visible sediment, algae growth, off-tastes, or odors. Cleaning involves draining the tank, scrubbing interior surfaces with a chlorine solution, rinsing thoroughly, and sanitizing before refilling. Professional cleaning costs $200-$500 depending on tank size and accessibility.
Need Help Sizing or Installing a Water Storage Tank?
We design and install complete water storage systems for wells throughout San Diego and Riverside Counties. Whether you need to compensate for a low-yield well, meet fire protection requirements, or add backup supply, we'll help you choose the right tank and configure your pumps for optimal performance.