By SCWS Team
Published February 17, 2026 · 9 min read
The casing is your well's backbone—a vertical pipe extending from ground surface down through loose soil and unstable formations. It keeps the hole open, prevents collapse, and protects groundwater from surface contamination. Choosing the right material and size affects well performance for decades.
Casing Materials at a Glance
- Steel: Strong, durable, traditional choice; susceptible to corrosion in some water
- PVC: Corrosion-proof, lighter, less expensive; requires stable formation
- Stainless steel: Premium option for corrosive water; highest cost
- Fiberglass: Specialty applications; rare in residential
Steel Casing
Steel has been the traditional casing material for over a century. Its strength allows it to support significant overburden, span voids, and withstand driving during installation. For deep wells or challenging geology, steel remains the standard.
Advantages of Steel
- Structural strength: Can be driven through obstacles and support unstable formations
- Durability: Handles stress during installation and use
- Versatility: Works in any geology
- Heat resistance: No concerns with temperature during installation
Disadvantages of Steel
- Corrosion: Susceptible to rust, especially in acidic or high-mineral water
- Weight: Requires heavier equipment to handle
- Cost: Generally more expensive than PVC
- Limited life in corrosive water: May need replacement in 20-30 years with aggressive water
PVC Casing
PVC (polyvinyl chloride) casing has become increasingly common for residential wells, especially in stable formations. Modern well-casing-grade PVC (Schedule 40 or SDR-21) provides excellent performance at lower cost.
Advantages of PVC
- Corrosion-proof: Won't rust regardless of water chemistry
- Lightweight: Easier handling and installation
- Lower cost: Typically 30-50% less than steel
- Smooth interior: Better flow characteristics
- Long lifespan: 50+ years with no corrosion concerns
Disadvantages of PVC
- Lower strength: Can't be driven; requires pre-drilling larger hole
- Temperature sensitivity: Softens at high temperatures (not for thermal wells)
- UV degradation: Surface exposure should be protected
- Not suitable for unstable formations: Needs stable hole conditions
Casing Diameter Selection
Diameter affects pump options, flow capacity, and future serviceability. Residential wells typically use 5" or 6" casing.
- 4-inch: Minimum for domestic wells in California; limits pump choices
- 5-inch: Most common residential size; accommodates 4" pumps with room
- 6-inch: Better flow, easier service, more pump options; slightly higher cost
- 8-inch+: For high-demand applications (irrigation, community wells)
Our recommendation: For new residential wells, 6-inch casing provides the best long-term value. The small additional cost buys easier pump service, better flow, and more equipment options.
California Requirements
California has specific requirements for well casing:
- Minimum diameter: 4 inches for domestic wells
- Grouting: Required for top 50 feet minimum or to first confining layer
- Surface seal: Must extend 2 feet above ground and be sloped away
- Wall thickness: Must meet specified standards (varies by diameter)
- Material approval: Both steel and PVC are acceptable when properly installed
Frequently Asked Questions
What is the best material for well casing?
Steel and PVC are both excellent choices for different situations. Steel offers superior strength and is required in unstable geology or where the casing must support significant weight. PVC is corrosion-resistant, lighter, less expensive, and suitable for most residential wells in stable formations. California allows both materials when properly installed to code.
How long does well casing last?
Steel casing typically lasts 25-50+ years depending on water chemistry—corrosive water shortens lifespan. PVC can last 50+ years as it doesn't corrode, though UV exposure at the surface should be minimized. Proper grouting and installation are more important than material choice for longevity. Failed seals cause more problems than casing material degradation.
What diameter well casing do I need?
Residential wells typically use 5-inch or 6-inch diameter casing. Larger diameter allows higher-capacity pumps and better flow, plus easier future service. The minimum depends on pump size—a 4-inch submersible pump requires at least 5-inch casing. California requires minimum 4-inch diameter for new domestic wells.
Does well casing need to be grouted?
Yes. California requires grouting (sealing) the annular space between the casing and borehole wall for at least the top 50 feet or to the first confining layer, whichever is deeper. Grouting prevents surface water from entering the well and contaminating groundwater. Neat cement or bentonite grout are typical materials.
Questions About Well Construction?
We can explain your well's construction and identify any concerns. New drilling, inspections, and service throughout San Diego and Riverside Counties.
Call (760) 463-0493